Dissertations / Theses: 'Root density; soil moisture'

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Pellegrini, André. "Sistemas de cultivo da cultura do fumo com ênfase às práticas de manejo e conservação do solo." Universidade Federal de Santa Maria, 2006. http://repositorio.ufsm.br/handle/1/5513.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Soil management systems with minimum tillage and mulch are predominant in agriculture of Southern of Brazil. No-tillage for tobacco crop is not common and restricted to isolated places and only for some farmers that, through empiric tests and adaptation of equipments, search for soil preservation and increased yield. The objective of this work was study the main soil management systems for tobacco crop and possibilities of changing the traditional system of tobacco cropping, with emphasis on practices of soil management and conservation to maintain the levels of yield and decrease the environmental impacts. Six treatments, in a completely randomized blocks design with three replicates, were installed: PC conventional till; CMP - minimum tillage rest; CMA - minimum tillage oat; PDcC no-tillage with camalhão; PDcCC no-tillage with consolidated camalhão; PDsC no-tillage without camalhão. The experiment was installed in a watershed, located in Agudo-RS city, in the agricultural year of 2004, in a Leptosol. The maim physical parameters were soil moisture, measured with a time domain reflectometer (TDR), in the depths of 0-0,06, 0,06-0,12 and 0,12-0,18 m, and soil temperature in the depth of 0,05 m, measured with datalogger and termopars, both during 87 days in the growth cycle; total porosity, macroporosity, microporosity, bulk density and soil water retention curve (CRA), determined in the depths of 0-0,06, 0,06-0,12, 0,12-0,18 and 0,18-0,24 m, 30 days after transplantion (DAT) and on 135 DAT, except for CRA, in the depths of 0-0,06 and 0,06-0,12 m; water and soil loss by runoff, determined for eight rain events, in two blocks, with on area of 1.2 m2 of collection; potassium and phosphorus, soluble and total were determined for seven rain events; the root system, the distribution in the cultural profile, nutrients availability in the exploration area, dry mass for soil volume and maximum depth of roots were determined; mechanical resistance of soil was determined with a manual penetrometer to verify the depth of the root impediment; measures of the plants included the leaf area, determination of plant height, number of leaves and yield for hectare. The conservation managements reduced soil and water losses, providing smaller amplitude in the daily temperature variation, larges soil moisture, but the yield was smaller than PDsC. This result for the PDsC was directly influenced by the shallower roots depth, which was a consequence of several factors, such as: presence of impediment layer; absence of ridge; nutrients in the surface and favorable initial conditions of soil temperature and moisture. However, there was great interaction among factors, turning complex the explanation of the results obtained; therefore, factors such as nutrients in the surface favored the losses of P and K soluble, decreasing their availability to plants; the impediment layer reduced the volume of soil explored by the roots and the ability for water storage, whereas the management systems PDcCC and PDsC were outside the upper or lower limit of water availability, in the layer of 0 to 0,06 m, for about 15 days. Sistemas de manejos do solo com o mínimo de revolvimento e com palha em superfície predominam na maioria dos cultivos agrícolas, no Sul do Brasil. A utilização do plantio direto na cultura do fumo está sendo iniciada, mas restrita a locais isolados e a alguns agricultores, que, via testes empíricos e adaptação de equipamentos, buscam preservar o solo e aumentar a produtividade. O objetivo deste trabalho foi estudar os principais sistemas de manejo do solo para a cultura do fumo e as possibilidades de mudança no sistema tradicional de cultivo de fumo, com ênfase às práticas de manejo e conservação do solo, mantendo os níveis de produtividade e diminuindo os impactos ambientais. O delineamento experimental foi blocos ao acaso com três repetições e seis tratamentos, sendo eles: PC - preparo convencional; CMP - cultivo mínimo pousio; CMA - cultivo mínimo aveia; PDcC - plantio direto com camalhão; PDcCC - plantio direto com camalhão consolidado; PDsC - plantio direto sem camalhão. O experimento foi implantado em uma microbacia hidrográfica, localizada no município de Agudo-RS, no ano agrícola de 2004, sobre em um Neossolo litólico eutrófico típico. Os principais avaliadores físicos foram umidade volumétrica do solo, medida com reflectômetro de domínio de tempo (TDR), nas profundidades de 0-0,06, 0,06-0,12 e 0,12-0,18 m, e temperatura do solo na profundidade de 0,05 m medida com datalogger e termopares, ambas durante 87 dias no período de crescimento; porosidade total, macroporosidade, microporosidade, densidade do solo e curva de retenção de água (CRA), realizadas nas profundidades de 0-0,06, 0,06-0,12, 0,12-0,18 e 0,18-0,24 m aos 30 dias após transplante (DAT) e aos 135 DAT, exceto CRA, nas profundidades de 0-0,06 e 0,06-0,12 m; perda de água e solo pelo escoamento superficial, determinados em oito chuvas, em dois blocos, com uma área de coleta de 1,2 m2; fósforo e potássio solúvel e total, em sete chuvas; no sistema radicular foram determinados a distribuição no perfil cultural, disponibilidade de nutrientes na região de exploração, massa seca por volume de solo e profundidade máxima das raízes; a resistência mecânica do solo determinada com um penetrômetro manual para diagnosticar a profundidade de impedimento radicular; medidas avaliadoras das plantas foram área foliar, comprimento de caule, número de folhas e produtividade por hectare. Os preparos conservacionistas reduziram as perdas de solo e água e proporcionaram uma menor amplitude na temperatura diária, maior umidade do solo, mas a produtividade no PDsC ficou aquém dos preparos convencionais. Esse resultado no PDsC foi diretamente influenciado pelo menor aprofundamento das raízes, sendo esse conseqüência de vários fatores como presença de camada de impedimento, não possuir camalhão, posicionamento mais superficial da adubação de base e condições iniciais favoráveis de temperatura e umidade do solo. Contudo, houve grande interação de fatores, tornando complexa a explicação do resultado obtido, pois fatores como a adubação superficial favoreceu as perdas de P e K solúvel, diminuindo a disponibilidade; a camada de impedimento diminuiu o volume de solo explorado pelas raízes e a capacidade de armazenamento de água, sendo que os manejos PDcCC e PDsC ficaram em torno de 15 dias fora da faixa de disponibilidade de água, na camada de 0 a 0,06 m.

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Omotere, Olumide Olubunmi. "Improvement of the Soil Moisture Diagnostic Equation for Estimating Root-Zone Soil Moisture." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157607/.

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Soil moisture information can be used accurately in determining the timing and amount of irrigation applied to plants. Pan and Pan et al. proposed a robust and simple daily diagnostic equation for estimating daily soil moisture. The diagnostic equation evaluates the relationship between the soil moisture loss function and the summation weighted average of precipitation. The loss function uses the sinusoidal wave function which employs day of the year (DOY) to evaluate the seasonal variation in soil moisture loss for a given year. This was incorporated into the daily diagnostic equation to estimate the daily soil moisture for a location. Solar radiation is an energy source that drives the energy and water exchanges between vegetation and the atmosphere (i.e., evapotranspiration), and thus impacts the soil moisture dry-down. In this paper, two parameters (the actual solar radiation and the clear sky solar radiation) are introduced into loss function coefficient to improve the estimation of soil moisture. After the Introduction of the solar radiation data into soil moisture loss function, a slight improvement was observed in the estimated daily soil moisture. Pan observed that generally the correlation coefficient between the estimated and the observed soil moisture is above 0.75 and the root mean square error is below 5.0 (%v/v). The introduction solar radiation data (i.e. clear sky solar radiation and actual solar) improve the correlation coefficient average for all the sites evaluated by 0.03 when the root mean square error is generally below 4.5(%v/v) for the entire root zone.

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Erindi-Kati, Anila. "Remote sensing and root zone soil moisture." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84027.

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This study investigated the possibility of three approaches in determination of soil moisture in the root zone. The aim of the study was to contribute to the development of soil moisture monitoring methods to better help crop best management practices. Two fields were examined, one at the Macdonald Campus of McGill University and the other near St. Jean-sur-Richelieau. Three approaches were used; (1) a hand-held hyper-spectral sensor (350-2500 nm), (2) a Geonics RTM EM-38 conductivity meter and, (3) gravimetric soil moisture sampling. The first experiment (at St. Jean-sur-Richelieu) investigated the possibility of monitoring soil moisture with the EM_38, in the presence of field elevation and soil texture. The second experiment (at Macdonald Campus) investigated the possibility of using hyper-spectral sensor data for determination of soil characteristics in the root zone, in the presence of such factors as (a) irrigation (main treatment), (b) nitrogen (sub-treatment), and (c) weed control (sub-sub-treatment). Statistical regression analyses and Artificial Neural Network models were used to select the best waveband region for determination of soil root zone moisture. The coefficients of determination obtained by the statistical analyses ranged from 0.75 to 0.94. The wavebands most frequently identified by these analyses ranged from 1100 nm-1900 nm. The performances of the ANN training models were considered acceptable (R2 from 0.6 to 0.8). The lack of sufficient data greatly impacts this approach.

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Dassanayake, Kithsiri Bandara. "Differential responses of perennial root systems to change in soil moisture." Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU089928.

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There is evidence in the literature that drought avoidance/tolerance in many annual crop plants is associated with root system characteristics. However, investigations on the morphological traits associated with drought resistance of tree crops is very limited. Identification of such traits would be useful in screening genotypes for drought tolerance. To assess the impact of environmental conditions on plant behaviour requires a carefully defined test environment, a procedure for monitoring changes in the environment and the testing of the test environment for reliability. The filter paper procedure was modified, calibrated and adopted to monitor soil water potential in experimental pots. A multi-compartmental pot system was developed to a create discontinuous soil water distribution. Wax and coarse sand were used to create spatially variable soil water potentials in adjacent pot compartments and the effects were assessed using broad bean as the test plant. Wax affected root morphology but sand did not. The vertically segmented pot set-up proved to be effective for the assessment of genotypic differences in rooting patterns in response to heterogeneously distributed soil water. Genotypic variations in morphology and growth patterns of whole root systems in coconuts were studied under favourable soil moisture conditions. The root systems of coconut cultivars varied in size, growth, patterns and in individual characteristics. Differences were apparently related to the drought tolerance of cultivars. Differences were associated with important differences in patterns of dry matter partition. Three coconut cultivars were evaluated in relations to root system responses to dehydration in the surface soil.

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Bellett-Travers, David Marcus. "Water relations and soil moisture requirements of transplanted amenity trees during establishment." Thesis, University of Hertfordshire, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251544.

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Newill, Paul Anthony. "Imaging of soil moisture in the root zone using capacitively coupled electrodes." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/imaging-of-soil-moisture-in-the-root-zone-using-capacitively-coupled-electrodes(24dbb858-3a0f-4fd7-8956-0070d2e47283).html.

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This research explores the use of insulated electrodes to determine electrical impedance distributions within soil cores. It is used to infer the effect of roots on soil moisture which, in turn, can provide knowledge relating to crop breeding programmes. These programmes are becoming increasingly important in order to address challenges posed by global population growth and climate change. Direct contact electrical impedance measurements in soil are frequently used but these are vulnerable to electrochemical effects and corrosion. Insulated electrodes are used in the present work to overcome these difficulties and a modified electrode model has been proposed. Measurements require the acquisition of spectroscopic complex impedance and extraction of the real impedance to infer soil moisture content. Calculated and simulated impedance, from the analytical solution and an FEM model respectively, were compared to measurements performed within a parallel-plate test cell containing saline solutions. The effects of moisture, compaction and temperature on soil impedance measurements have been explored. Finally, two growth trials using maize plants and control vessels were performed to create 2D images of impedance distributions, from which moisture placement was inferred. Results show that for saline electrolytes, the insulated electrode method was capable of estimating the impedance of tap water to within 10% of calibrated laboratory equipment. For soil based measurements, the variation of moisture content from 5-30% resulted in a 1000-fold decrease in impedance. The change was most significant in drier soils. For compaction based testing, at 5% moisture content soil impedance decreased by approximately 40%, compared to only 20% in the wettest samples. Temperature testing revealed an impedance change of approximately 2%/ °C, in agreement with earlier reports. Plant growth trials revealed increases in electrical impedance due to soil drying from an initial value of 1-2kΩ when the soil was wetted to field capacity, to as much as 60kΩ when dry. Only small changes were evident in the control vessels. It was also found that areas exposed to potential evaporation, such as at the surface closest to the plant stem, suffered significant losses in moisture content, reaching as high as 15-20kΩ. This research utilises a measurement technique which has not previously been used to measure soil impedance to infer moisture content. The research also found that the scaling of a thin layer within an FEM model can significantly reduce computational demands, while retaining accuracy, and allow more complex FEM simulations to be performed on a less powerful computer.

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Evans, Douglas. "Soil water regime, root water extraction and the growth of fine roots of Sitka Spruce." Thesis, University of Aberdeen, 1988. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU020973.

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The effect of removing soil water stress on fine root growth and the pattern of water use was studied by irrigating a small plot (20 m x 20 m) of 40 year old Sitka spruce. A control plot was established close by. Soil water content and soil matric potential were measured independently on both plots at several depths. Root growth was measured using monthly coring for the surface horizons (c. 10 cm depth) and ingrowth cores to study rooting at depth. In the absence of irrigation the 2 plots had similar water regimes. The irrigation kept matric potential > 20 kPa and water content > 20%. Areas between trees were wetter than areas close to stems and wetted up more during periods of rainfall. This is in contrast to young plantations where stemflow accounts for a much larger proportion of precipitation reaching the forest floor. At field capacity most of the water uptake was from near the surface but as the profile dries the proportion from depth increases, at the end of a dry period 50% of uptake was from the bottom half of the rooted zone. Water uptake from below the rooted zone was small. Irrigation had a significant effect on root tip density and on small root mass but not on fine and dead root masses. Root tip density stayed high through the summer with irrigation but fell on the control plot, the number of tips began to increase earlier on the control plot. This is interpreted as irrigation increasing the longevity of tips from 2-3 months (control) to 5 months. Rewetting of the soil in autumn appears to act as a cue for an increase in root growth. Irrigation had no effect on root growth at depth and there was no difference in growth at different depths on either plot.

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Zhang, Hongjuan [Verfasser]. "Improved characterization of root zone soil moisture by assimilating groundwater level and surface soil moisture data in an integrated terrestrial system model / Hongjuan Zhang." Jülich : Forschungszentrum Jülich GmbH, Zentralbibliothek, 2018. http://d-nb.info/1163839310/34.

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Snelson, Jonathan Bundy. "Plant Growth and Root Zone Management of Greenhouse Grown Succulents." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32398.

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Effects of media, soil moisture, fertility rate, and plant growth regulators on plant growth were investigated for 13 taxa of succulents. Media: Liners were grown in five common greenhouse substrates: 80% peat, 60% bark + 30% peat moss, 80% pine bark/20% Permatil (v/v), 100% composted pine bark, or whole tree substrate until market ready. Overall, higher percentage bark mixes yielded smaller plants, with lower shoot dry weights, shoot heights and widths. Soil Moisture: Liners were potted into a 60% bark/30% peat soilless potting mix. In group 1 , irrigation to container capacity occurred when volumetric soil moisture content fell below 30%, 20%, or 10%,. Group two (seven species) irrigation thresholds were shifted to 35%, 25%, and 15%. Effects of irrigation rate were significant in three of the 13 species studied, and those effects were species-specific. Fertility Rate: Liners were potted into60% bark/30% peat substrate. Fertility reatments in group were 0, 50, 100, or 200 mg.L-1 nitrogen. Group 2 plants received treatments of 50, 150, 250, or 350 mg.L-1 nitrogen. Four of the 11 species studied were affected by nitrogen rate, with rates up to 200 mg.L-1 generally producing the largest plants. PGRs: Seven species were potted into a 60% bark/30% peat substrate. Group one plants were treated with a foliar application of benzyladenine (Configure) at rates of 0, 400, 800, or 1600 mg.L-1. Group 2 plants were treated either BA at 0, 250, 500, or 1000 mg.L-1, dikegulac sodium (Augeo) at 400, 800, or 1600 mg.L-1, or a tank mix of 500 mg.L-1 Configure and 800 mg.L-1 Augeo. BA caused an increase in branches leaders or offsets in two species. Master of Science

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Pijl, Isabelle. "Drip fertigation : effects on water movement, soil characteristics and root distribution." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52245.

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Thesis (MScAgric)--University of Stellenbosch, 2001. ENGLISH ABSTRACT: The application of water and nutrients via a drip irrigation system influences the water distribution in the soil, soil characteristics and root distribution beneath the dripper. To determine the water distribution pattern beneath a dripper in sandy soil, EnviroSCAN (Sentek) capacitance probes were installed directly below the dripper and at distances of 20, 40 and 60 cm from the dripper. The continuous monitoring of the soil water content (SWC) beneath the dripper provided a good indication of how the water applied through the dripper is distributed in the soil. In this study a semi-impermeable layer in the soil was detected through observing water accumulation patterns in the SWC. Water accumulated above the layer and SWC values increased to far above the upper level of easily available soil water (EAWupper),while the lower soil layers remained drier. The measurements also show that the horizontal water movement is restricted to 20 cm from the dripper. Specific parameters, such as the lower level of easily available soil water (EAWlower),can be used to determine optimal irrigation management. Together with the water distribution study, the root distribution beneath a dripper was also investigated. A high concentration of roots in the area beneath the dripper was found, which corresponds with the area wetted by irrigation. In another study, three irrigationlfertigation methods where investigated to ascertain the influence on soil characteristics and root distribution. These were: micro irrigation (MI) (micro-spinner irrigation with broadcast granular fertilization), conventional drip fertigation (CDF) (daily drip irrigation with daily or weekly fertigation with a unbalanced nutrient solution, containing macronutrients only) and daily drip fertigation (DDF) (daily fertigation of a balanced nutrient solution, containing macro- and micronutrients). The study was conducted in two locations, viz. in the Western Cape Province, on sandy soil, and in the Eastern Cape Province, on silt loam soil. Micro Irrigation: A wide and even root distribution in the entire wetted volume was found on the sandy and silt loam soil. On the sandy soil, the soil pH(KC1)directly beneath the spinner was significantly lower than the pH(KC1)at positions further away from the spinner. Conventional Drip Fertigation: Root studies on sandy soil indicate a poor root development beneath the dripper, with a high concentration of roots in the area between the drippers. The poor root development directly beneath the dipper may be due to oxygen deficiency and/or acidification beneath the dripper. The soil pH(KC1)values show a significant lower pH(KC1)value directly beneath the dripper than further away. In comparison to the sandy soil, the roots developed well beneath a dripper in a silt loam soil. It appears as if soil acidity and/or oxygen deficiency was not a problem on this soil type. The rest of the root system was also well developed. This may be due to this soil's higher water holding capacity which creates a bigger wetted zone. Daily Drip Fertigation: In the sandy soil it seems that the roots developed in a continuous column beneath the dripper line, with little root development further than 20 cm from the dripper line. Where over-irrigation occurred, it caused a poor root development directly beneath the dripper. The root density in this treatment was much higher than in the other two treatments. The use of a balanced nutrient solution and pulse irrigation may be reasons for the better root development. In a silt loam soil a very high concentration of roots was found beneath the dripper and the rest of the root system was also well developed. As with the CDF treatment, it appears as if oxygen deficiency was not a problem on this soil type. AFRIKAANSE OPSOMMING: Die toediening van water en voedingstowwe deur 'n drip-besproeiings stelsel beïnvloed die waterverspreiding in die grond sowel as die grondeienskappe en wortelverspreiding onder die dripper. Die waterverspreiding onder 'n dripper in 'n sandgrond is bepaal deur EnviroSCAN kapasitansie meetpenne direk onder die dripper en 20, 40 en 60 cm van 'n dripper af te installeer. Die aaneenlopende monitering van die grondwaterinhoud het 'n goeie indikasie van waterverspreiding in die grond gegee. Die horisontale waterbeweging is grootliks beperk tot 'n 20 cm radius vanaf die dripper en die waterbeweging was hoofsaaklik in 'n vertikale rigting. Die teenwoordigheid van 'n semi-deurlaatbare grondlaag in die grondprofiel is opgemerk deur water-akkumulasie in die profiel waar te neem. Wortelverspreiding onder die dripper is ook ondersoek en 'n hoë konsentrasie wortels is in die benatte sone gevind. In 'n verdere studie is drie besproeiings/sproeibemestings behandelings gebruik om die invloed van besproeiing/sproeibemesting op grondeienskappe en wortelverspreiding te ondersoek. Die drie behandelings was: mikro-besproeiing (mikro-besproeiing met korrelbemesting), konvensionele-drip-sproeibemesting (daaglikse drip-besproeiing met daaglikse of weeklikse sproeibemesting van 'n ongebalanseerde, voedingsoplossing wat alleenlik uit makro-elemente bestaan) en daaglikse-drip-sproeibemesting (daaglikse drip-besproeiing met daaglikse sproeibemesting van 'n gebalanseerde voedingsoplossing wat mikro- en makro-elemente bevat). Die studie is in twee areas gedoen, een in die Wes-Kaap, op 'n sandgrond, en die ander in die Oos-Kaap, op 'n slik-leemgrond. Mikro-besproeiing: Die wortelverspreidings studies op die sand- en slik-leemgrond wys op 'n wye en eweredige wortelontwikkeling in die totale benatte volume. Op die sand grond is gevind dat die grond pR(KCl)direk onder die sproeiertjie betekenisvol laer was as die pR(KCl)waardes verder weg van die sproeiertjie. Konvensionele-drip-sproeibemesting: Die wortelverspreiding in die sandgrond wys op geringe wortelontwikkeling direk onder die dripper met die hoogste konsentrasie wortels tussen die drippers. Grondversuring en/of suurstoftekorte onder die dripper kan die oorsaak wees van die swak wortelontwikkeling direk onder die dripper. Die grond pR(KCl)direk onder die dripper was betekenisvol laer as die pR(KCl)verder weg van die dripper. In vergelyking met die sandgrond, het die wortels in die slik-leemgrond goed ontwikkelonder die dripper. Dit wil voorkom of versuring en suurstoftekorte onder die dripper nie 'n probleem was in die slik-leemgrond nie. Die res van die wortelstelsel was ook goed ontwikkel. Dit mag wees weens die grond se hoë waterhoudingsvermoë wat 'n groot benatte area tot gevolg het. Daaglikse-drip-sproeibemesting: In die sand grond wil dit voorkom asof die wortels in 'n aaneenlopende kolom onder die dripperlyn ontwikkel met weinig wortelontwikkeling verder as 20 cm van die dripperlyn. Waar oorbesproeiing 'n probleem was, was daar weinig wortelontwikkeling in 'n klein area direk onder die dripper. Die wortel-digtheid in die behandeling was baie hoër as in die ander behandelings. Die gebruik van 'n gebalanseerde voedingsoplossing en puls-besproeiing mag dalk redes wees vir die beter wortelontwikkeling. In die slik-leemgrond is 'n hoë konsentrasie wortels onder die dripper gevind en die res van die wortelstelsel was ook goed ontwikkel. Soos in die konvensionele-drip-sproeibemesting behandeling wil dit voorkom of suurstoftekort en versuring onder die dripper nie 'n probleem was in die grond nie.

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Costa, Carlos Alexandre Gomes. "Soil moisture and water availability in the root zone under natural conditions of preserved Caatinga." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8261.

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico A Ãgua na bacia hidrogrÃfica estÃ distribuÃda em diversos compartimentos importantes no que se refere Ã ecohidrologia. Muitos estudos em regiÃes semiÃridas apontam os reservatÃrios superficiais como principais compartimentos de Ãgua. Entretanto, a bacia hidrogrÃfica tem maior abrangÃncia que as bacias hidrÃulicas nela contida, e os recursos hÃdricos nos compartimentos distribuÃdos na bacia hidrogrÃfica (como no solo) devem ser analisados nÃo somente no que se refere aos usos ecolÃgicos, mas tambÃm como espaÃo de disponibilidade hÃdrica. Portanto, o objetivo do trabalho foi analisar, com base em medidas e modelagem, a dinÃmica da Ãgua nos solos de uma bacia semiÃrida de Caatinga preservada e seu impacto sobre a disponibilidade hÃdrica. Para isso foi medida, entre outros, a umidade do solo a cada hora, de 2003 a 2010 (2923 dias) na Bacia Experimental de Aiuaba (BEA, 12 kmÂ), totalmente preservada e com precipitaÃÃo mÃdia anual de 560 mm. O monitoramento foi realizado atravÃs de trÃs sensores TDR, um instalado em cada uma das trÃs associaÃÃes entre solo e vegetaÃÃo (SVA) identificadas na bacia. O mÃtodo de investigaÃÃo considerou seis etapas principais: i) determinaÃÃo da profundidade efetiva das raÃzes da Caatinga preservada; ii) calibraÃÃo dos sensores de umidade tipo TDR; iii) representaÃÃo espaÃo-temporal da umidade do solo em cada unidade de SVA; iv) anÃlise da disponibilidade hÃdrica do solo na zona das raÃzes; v) parametrizaÃÃo do modelo hidrolÃgico WASA-SED; e vi) parametrizaÃÃo do modelo hidrolÃgico DiCaSM. Os resultados obtidos nesta pesquisa indicam a importÃncia da abordagem da anÃlise temporal da umidade do solo e da disponibilidade hÃdrica do solo na zona das raÃzes para a manutenÃÃo do bioma Caatinga. Mais especificamente, foi observado que a profundidade efetiva do sistema radicular na BEA oscilou entre 70 e 80 cm nas regiÃes com solos profundos, porÃm, em regiÃes com solos rasos, observou-se que a profundidade efetiva das raÃzes adaptou-se Ãs restriÃÃes, ficando reduzida a menos de 40 cm. AlÃm disso, a anÃlise sazonal demonstrou que, na estaÃÃo de estio, as raÃzes tÃm comprimentos atÃ 11 cm menores, abrindo, portanto, poros secundÃrios que facilitarÃo a penetraÃÃo da Ãgua nas eventuais chuvas dos meses secos (junho a dezembro), assim como nas primeiras chuvas da estaÃÃo Ãmida. Nas duas SVAs cujos solos sÃo profundos e cuja vegetaÃÃo Ã densa, a Ãgua no solo encontra-se ânÃo-disponÃvelâ (isto Ã, abaixo do ponto de murcha permanente â WP) em quase nove meses ao ano (72% do tempo); e somente durante trÃs meses ao ano (25%) a Ãgua no solo encontra-se disponÃvel. Nos 3% restantes do ano (cerca de 10 dias) hÃ Ãgua gravitacional nessas SVAs. Na SVA cujo solo Ã raso e cuja vegetaÃÃo Ã esparsa, a dinÃmica da Ãgua no solo Ã diferente: o tempo em que hÃ Ãgua gravitacional, disponÃvel e nÃo disponÃvel Ã praticamente o mesmo (quatro meses ao ano). Isso se deve, entre outros, Ã baixa umidade do solo no ponto de murcha permanente do neossolo litÃlico; e Ã sua restrita espessura, gerando saturaÃÃo muito mais frequentemente que nos demais solos que â ao contrÃrio deste â dispÃem de drenagem profunda. A depleÃÃo da Ãgua no solo sob condiÃÃes de umidade abaixo do ponto de murcha foi outro resultado importante desta pesquisa. Nas duas associaÃÃes com solos profundos e vegetaÃÃo densa, observou-se â ao longo de todo o perÃodo investigado â decaimento contÃnuo da umidade atÃ que a mesma se aproximasse assintoticamente da umidade residual. AnÃlise mais detalhada demonstrou que a reduÃÃo da umidade do solo entre o WP e a umidade residual sempre obedecia ao decaimento exponencial. Na associaÃÃo com solo raso e vegetaÃÃo esparsa observou-se que a umidade nÃo caÃa para valores inferiores ao WP, mesmo sujeita ao mesmo rigor climÃtico das demais associaÃÃes. Considerando-se: (i) que em solo tÃo seco, a drenagem Ã improvÃvel; e (ii) que os processos associados de percolaÃÃo e evaporaÃÃo tampouco devam ser os responsÃveis pela retirada de Ãgua do solo (posto que o fenÃmeno nÃo se observa na SVA cujo solo Ã raso e, portanto, mais quente); levanta-se a hipÃtese que o secamento do solo nessas condiÃÃes deva ser causado por extraÃÃo de Ãgua pela vegetaÃÃo. Isso reforÃaria a tese de que a Caatinga dispÃe de adaptaÃÃo para sobreviver mesmo em condiÃÃes de estresse hÃdrico. Os modelos hidrolÃgicos WASA-SED e DiCaSM nÃo conseguiram representar adequadamente a dinÃmica temporal da Ãgua nos solos da BEA. No entanto, os modelos reproduziram satisfatoriamente as curvas de permanÃncia da umidade dos solos, permitindo representar a disponibilidade hÃdrica na zona das raÃzes para fins de planejamento. Por fim, logrou-se avaliar â quantitativa, espacial e temporalmente â a disponibilidade hÃdrica do solo. Esta Ã da mesma ordem de grandeza da disponibilidade de um reservatÃrio superficial Ãtimo. Em termos quantitativos, a disponibilidade no solo chega a ser quase cinco vezes superior Ã do reservatÃrio superficial, entretanto, a garantia associada da Ãgua superficial (90%) Ã bem superior Ã permanÃncia da Ãgua disponÃvel na BEA: apenas 28% nas Ãreas com solos profundos e 65% nas Ãreas com solos rasos. Regarding ecohydrology, the catchment water is distributed over several important compartments. Many studies in semiarid re gions indicate the surface reservoirs as the main water compartments. However, the watershed has greater scope than the water reservoirs contained therein, and water resources in compartments distributed in the watershed (like in soil) should be analyzed not only with regard to ecological uses, but also as spaces of water availability. Therefore, the object ive of this work was to analyze, based on measurements and modeling, the water dynamics in th e soils of a semi-arid basin in preserved Caatinga, and its impact on water availability. Wit h this in mind, it was measured, among others, the soil moisture, every hour, from 2003 to 2010 (2923 days) in the Aiuaba Experimental Basin (AEB, 12 km Â), fully preserved and with average annual rainfall of 560 mm. Monitoring was carried out through three TDR se nsors, one installed in each of the three soil and vegetation associations (SVA) identified in the basin. The research method considered six main steps: i) assessment of the eff ective root depth of preserved Caatinga ii) calibration of humidity TDR sensors iii) space-time representation of soil moisture in each SVA unit iv) analysis of soil water availability in the root zone, v) parameterization of the WASA-SED hydrological model, and vi) parameterizati on of the DiCaSM hydrological model. The results of this research indicate the importance of addressing the temporal analysis of soil moisture and soil water availability in the root zone to maintain the Caatinga biome. More specifically, it was observed that the effecti ve depth of the root system on AEB ranged between 70 and 80 cm in areas with deep soils, but in areas with shallow soils, it was observed that the effective depth of the roots had adapted to the constraints, having been reduced to less than 40 cm. Furthermore, the season al analysis showed that in the dry season, the roots have lengths up to 11 cm smaller, openin g, therefore, secondary pores that facilitate the penetration of what little rain water falls in the dry months (June-December), as well as in the first rains of the wet season. In the two SVAs whose soils are deep and the vegetation is dense, the soil water is 'not available' (ie below the permanent wilting point - WP) during nearly nine months a year (72% of the time), and on ly during three months of the year (25% of the time) the soil water is available. In the re maining 3% of the year (about 10 days) there is gravitational water in these SVAs. In the SVAs whose soil is shallow and whose vegetation is sparse, the dynamics of soil water are different : the time when there is gravitational water, available and unavailable, is practically the same (four months a year). This is due to, among other things, the low soil moisture at the permanen t wilting point of the Udorthent, and to its limited thickness, generating saturation much more frequently than in others that - unlike this one - have deep drainage. The depletion of soil wat er under conditions of moisture below the wilting point was another important result of this research. In the two associations with deep soils and thick vegetation, it was observed â throu ghout the observation period â continuous fall of moisture level until it approached asymptot ically the residual moisture. More detailed analysis showed that the reduction of soil moisture between the WP and the residual moisture level always followed the exponential decay. It was observed, in the association of shallow soil and sparse vegetation, that the moisture did not fall to below the WP, even subjected to the same rigorous climate of the other associations . Considering: (i) that in such a dry soil, the drainage is unlikely, and (ii) that the associated processes of percolation and evaporation should not be responsible for the removal of soil w ater either (since the phenomenon is not observed in SVAs whose soil is shallow and therefor e warmer) , it is raised the hypothesis that the soil drying under these conditions must be caused by water extraction by vegetation. This would strengthen the argument that the Caating a has adapted to survive under water stress. The hydrological models WASA-SED and DiCaSM failed to adequately represent the temporal dynamics of soil water in the AEB. However , the models did satisfactorily reproduce the retention curves of soil moisture, al lowing the representation of the water availability in the root zone for planning purposes . Finally, we managed to evaluate - quantitatively, spatially and temporally â the soil water availability. This availability is of the same order of magnitude of the availability of an o ptimal surface reservoir. The availability in the soil, in quantitative terms, can be almost five times higher than that of the surface reservoir. However, the security associated with su rface water (90%) is much higher than the water permanence available in the AEB: just 28% in areas with deep soils and 65% in areas with shallow soils.

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Goble, Peter. "Maximizing the utility of available root zone soil moisture data for drought monitoring purposes in the Upper Colorado River Basin and western High Plains, and assessing the interregional importance of root zone soil moisture on warm season water." Thesis, Colorado State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10139009.

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Root Zone Soil Moisture (RZSM) data have both drought monitoring and seasonal forecasting applications. It is the lifeblood of vegetation, an integral component of the hydrologic system, a determining factor in irrigation requirements, and works to govern the means by which energy imbalances are settled between land and atmosphere. The National Integrated Drought Information System (NIDIS) has worked in conjunction with the Colorado Climate Center to improve regional drought early warning through enhanced monitoring and understanding of RZSM. The chief goals of this research have been as follows: 1. Examine regional drought monitoring in the Upper Colorado River Basin and eastern Colorado with specific inquiry as to soil moisture’s role in the process. 2. Develop operational products that can be used to improve the weekly drought monitoring process in the Upper Colorado River Basin and eastern Colorado with an emphasis on utilization of soil moisture data. 3. Review in-situ soil moisture data from high elevation Snow Telemetry measurement sites in Colorado in order to understand the descriptive climatology of soil moisture over the Colorado Rockies. 4. Compare output from soil sensors installed by the Snow Telemetry and Colorado Agricultural Meteorological Network using current calibration methods in order to better understand application of direct comparison between output from the two different sensor types. Engineer a soil moisture core measurement protocol that is reliable within ten percent of the true volumetric water content value. This protocol, if successful on a local plot, will be expanded to alpha testers around the United States and used by the USDA for drought monitoring as well as NASA for ground validation of the Soil Moisture Active Passive (SMAP) Satellite. 5. Expose the seasonality and spatial variability of positive feedbacks that occur between RZSM and the atmosphere across the Upper Colorado River Basin and western High Plains using reanalysis data from the North American Land Data Assimilation System Phase-2 (NLDAS). Regional drought monitoring was found to involve assimilation of data from a bevy of sources. The decision-making process includes assessment of precipitation, soil moisture, snowpack, vegetative health, streamflow, reservoir levels, reference evapotranspiration, surface air temperature, and ground reports from the regional agricultural sector. Drought monitoring was expanded upon in this research through the development of several products intended for future Colorado Climate Center use. In-situ soil moisture timeseries are now being created from select SNOTEL and SCAN measurement sites. Reservoir monitoring graphics are being produced to accompany spatial analyses downloaded from the bureau of reclamation. More soil moisture data is being used, and now come from an ensemble of models rather than just the VIC model. While only ten years of data were collected in analyzing the descriptive soil moisture climatology of the Colorado Rockies, these data were telling in terms of the expected seasonal cycle of soil moisture at high elevations. SNOTEL measurements reveal that soil moisture levels peak prior to snowmelt, large decreases in soil moisture are expected in June and early July, a slight recovery is anticipated in association with the North American Monsoon, and the sign of near-surface water balance flips back to positive in the first two weeks of September before soils freeze. Seasonal variance and distribution of volumetric water content varies in ways that are useful to understand from a drought monitoring standpoint. The data show that measurements are affected when soil freezes. Comparing output from soil sensor relays using sensor types and calibration methods consistent with current SNOTEL and CoAgMet specifications revealed large differences in output regardless of being subject to the same meteorologic conditions. Soil moisture measurement protocol development proved to be a trial and error process. The data collected at Christman Field was not sufficient proof that soil coring results did come within ten percent of ground truth perhaps due to microscale variations in infiltration. It was possible to develop a protocol of an acceptable standard that could be followed by citizen scientist for an estimated cost of $50. Results from statistical modeling of post-processed NLDAS data from the last 30 years point primarily to a time frame between May and July in which soil moisture anomalies become significantly correlated with seasonal temperature and precipitation anomalies. This time of year is partially characterized by a climatologic maximization of downwelling solar radiation and a northward recession of the polar jet, but also precedes the anticipated arrival of the North American Monsoon. (Abstract shortened by ProQuest.)

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Peruzzo, Luca. "Geoelectrical approaches for characterizing soil geochemical processes and soil-root interactions." Thesis, Bordeaux 3, 2019. http://www.theses.fr/2019BOR30015.

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Cette thèse porte sur les possibilités que les méthodes d’imagerie géoélectrique offrent à la fois pour la caractérisation des processus géochimiques mais aussi pour l’étude d’interaction sol-racines. La ligne conductrice de ce travail, repose sur la position centrale de la qualité des sols et des interactions racines-sols dans de nombreux problèmes environnementaux. En effet, un nombre croissant d’études rapportent l’importance des interactions mutuelles entre les racines et le sol. Dans cette optique, cette thèse explore l’utilisation le développements approfondis de méthodes géoélectriques. Les processus physico-chimiques ainsi que les interaction sol-racines sont à l’origine de mouvement d’eau et de soluté, d’altération de la structure des sols ainsi que de perturbations biologiques. Les méthodes géoélectriques sont potentiellement sensibles à ces modifications hydrologique et biochimique. La méthode de Polarisation Provoquée Spectrale (PPS) a été combinée avec des analyses et des modélisations géochimiques permettant de connaitre sa sensibilité à la composition du fluide interstitiel (contenu dans l’espace poral), du pH et de la force ionique. Plus particulièrement, la signature PPS de la substitution Na+/Cu2+ a été analysée car il s’agit d’un critère pertinent traduisant la qualité d’un sol et reconnu mondialement. L’analyse PPS a été réalisée sur un sable (silicate) saturé et pour des concentrations typiques de Na+/Cu2+ que l’on trouve classiquement dans des sols exposés à des utilisations de pesticides au Cuivre (Cu). Les résultats ont montré que le pH et la force ionique ont été les variables prépondérantes contrôlant le signal PPS, alors que des effets négligeables sont liés à la substitution Cu/Na. L’utilisation simultanée d’analyses chimiques et géophysiques en laboratoire a permis de mieux caractériser les processus de complexation étudiés et d’appuyer considérablement l’interprétation des signaux PPS. Enfin, la tomographie de résistivité électrique et la méthode de Mise-A-La-Masse ont été combinées pour développer une nouvelle approche d'imagerie du chemin préférentiel emprunté par le courant électrique dans le système racines-sols. Etant donné que la conduction électrique dans le sol et les racines est principalement électrolytique, l'approche proposée repose sur le mouvement de l'eau et des solutés dans le système racines-sol. Le potentiel de la méthode pour son application in-situ a été testée à l’aide d’une série d’expériences sur une vigne. À la suite des résultats prometteurs, la méthode a été développée et appliquée lors d’une expérience en laboratoire portant sur la croissance racinaire dans un rhizotron de plantes de coton et de maïs. La méthode s'est révélée sensible aux différences physiologiques entre les espèces et éventuellement à la réponse de la plante aux facteurs de stress environnementaux. De nouvelles expériences contrôlant les variables physiologiques des tissus racinaires sont nécessaires pour une meilleure compréhension de leurs influences. Les développements technologiques récents soutiennent fortement la diffusion de l’imagerie et du suivi géoélectriques à l'échelle du terrain. Dans ce contexte prometteur, les résultats de cette thèse contribuent au développement d'approches géoélectriques pour l'étude du sol et de ses interactions mutuelles avec les racines des plantes à des échelles spatio-temporelles pertinentes In this thesis I investigate some of the possibilities offered by the use of geoelectrical methods for characterizing soil geochemical processes and root-soil interactions. The motivation for this thesis arises from the pivotal role of soil quality and root-soil interactions in manifold environmental issues. In addition, there is growing evidence of the importance of mutual interactions between roots and soil, for this reason this thesis explores the use of geoelectrical methods for more comprehensive approaches. Both soil physicochemical processes and root-soil interactions involve, among others, the movement of water and solutes, altercations of the soil structure, and biological feedbacks. Geoelectrical methods are potentially sensitivity to these hydrogeological and biogeochemical modifications. The Spectral Induced Polarization (SIP) method was combined with geochemical analyses and modeling in order to investigate its sensitivity to pore fluid composition, pH, and ionic strength. In particular, the SIP signature of Na+/Cu2+ substitution was investigated because of their worldwide relevance for soil quality. The SIP investigation focused on saturated silica, and explored concentrations of Na+ and Cu2+ that are typical to agricultural soils exposed to the use of Cu pesticides. The results showed how pH and ionic strength were the main variables controlling the SIP signals, while negligible effects were related to the Cu/Na substitution. The concurrent use of chemical and geophysical laboratory experiments allowed a better characterization of the investigated complexation processes and significantly supported the interpretation of the SIP signals. The Electrical Resistivity Tomography and the Mise-A-La-Masse methods were combined to develop a novel approach for imaging the electric current pathways in the root-soil system. Since the current conduction in soil and roots is mostly electrolytic, the proposed approach relates to the movement of water and solutes within the root-soil system. The potential of the method for field investigations was explored with a set of experiments on a grapevine. In light of the promising results, the method was further developed and applied to rhizotron laboratory experiments on cotton and maize plants. The method proved to be sensitive to inter-species physiological differences and possibly to the plant response to environmental stressors. New experiments with physiological analyses of root tissues are needed to elucidate these aspects. Emerging technologies are strongly supporting to the diffusion of imaging and monitoring geoelectrical applications at the field-scale. In this promising context, the results of this thesis contribute to the development of geoelectrical approaches for studying soil and its mutual interactions with plant roots over relevant spatiotemporal scales

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Alhabeeb, Abdulrahman S. I. "Effects of irrigation and plant density on growth and yield of faba bean (Vicia Faba L.)." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267430.

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15

Arvelo, Andres. "EFFECTS OF THE SOIL PROPERTIES ON THE MAXIMUM DRY DENSITY OBTAINED FRO." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2966.

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In the construction of highways, airports, and other structures, the compaction of soils is needed to improve its strength. In 1933 Proctor developed a laboratory compaction test to determine the maximum dry density of compacted soils, which can be used for specifications of field compaction. The Compaction of soils is influenced by many factors, the most common are the moisture content, the soil type and the applied compaction energy. The objective of this research is the analysis of the maximum dry density values based on the soil classification and characterization. The method of choice in the determination of the maximum dry density from different soils was the Standard Proctor Test following the procedure for the standard Proctor test as is explained in ASTM Test Designation D-698. From this investigation, the maximum dry density of eight types of sands was obtained, the sands were classified by using the Unified Soil Classification System. The influence on the maximum dry density of the type of sands, type of fines, amount of fines and distribution of the grain size was determined, followed by a sensitivity analysis that measured the influence of these parameters on the obtained maximum dry density. The research revealed some correlations between the maximum dry density of soils with the type of fines, the fines content and the Uniformity Coefficient. These correlations were measured and some particular behavioral trends were encountered and analyzed. It was found that well-graded sands have higher maximum dry density than poorly graded when the soils have the same fines content, also it was encountered that plastic fines tend to increase the maximum dry density. M.S.C.E. Department of Civil and Environmental Engineering Engineering and Computer Science Civil Engineering

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Kingsley-Richards, Sarah. "Influence of Plant Age, Soil Moisture, and Temperature Cylcing Date on Containter-Grown Herbaceous Perennials." ScholarWorks @ UVM, 2011. http://scholarworks.uvm.edu/graddis/122.

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Perennial growers overwintering plant stock require information to assist in deciding which containerized plants are most likely to successfully overwinter. Three studies on container-grown herbaceous perennials were conducted to examine the influence of plant age, soil moisture, and temperature cycling date on cold hardiness. In January, plants were exposed to controlled freezing temperatures of -2, -5, -8, -11, and -14C and then returned to a 3-5C greenhouse. In June, plants were assessed using a visual rating scale of 1-5 (1 = dead, 3-5 = increasing salable quality, varying by cultivar) and dry weights of new growth were determined. Controlled freezing in November and March were also included in the third study. In the first study, two ages of plants were exposed to controlled freezing temperatures in January. For Geranium x cantabrigiense 'Karmina', age had no effect on either rating or dry weight in one study year. In two Sedum 'Matrona' study years, age had no effect on dry weight but ratings were higher for older plants than younger plants in the first year and higher for younger plants than older plants in the second year. In two Leucanthemum x superbum 'Becky' study years, age had an effect on both rating and dry weight which were both generally higher for younger plants than older plants. In the second study, plants were maintained in pots at two different soil moisture levels prior to exposure to controlled freezing temperatures in January. Coreopsis 'Tequila Sunrise' and Carex morrowii 'Ice Dance' showed no effect on either rating or dry weight from soil moisture level. Soil moisture level had no effect on dry weight but ratings were higher for Geranium x cantabrigiense 'Cambridge' “wet” plants and for Heuchera 'Plum Pudding' “dry” plants. Carex laxiculmus 'Hobb' (Bunny Blue™) soil moisture level had an effect where dry weight was higher for “dry” plants. Means at were of salable quality for Geranium and Heuchera at all temperatures and Carex laxiculmus at temperatures above -11C. The effects of soil moisture level on Carex oshimensis were inconclusive. In the third study, during November, January, and March, plants were subjected to temperature cycling treatments prior to exposure to controlled freezing temperatures. Geranium x cantabrigiense 'Cambridge' were more tolerant of both temperature cycling and freezing temperatures in January and an increased number of cycles in November had an advantageous effect. Sedum 'Matrona' were more tolerant of temperature cycling and freezing temperatures in January and an increased number of cycles in March had an advantageous effect. Leucanthemum x superbum 'Becky' were more tolerant of temperature cycling in January in the second year of the study and an increased number of cycles in November had an advantageous effect in the first year and in all months in the second year. Overwintering younger container-grown plants is likely to result in more growth and higher quality following exposure to freezing temperatures. Effects of soil moisture level on overwintering container-grown plant growth and quality are cultivar-specific and a general effect could not be established in these studies. Overwintering container-grown plants are likely to be hardier in January and slight temperature cycles prior to exposure to freezing temperatures generally increase hardiness.

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17

Siegel-Issem, Cristina Marie. "Forest Productivity as a Function of Root Growth Opportunity." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/36323.

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Compaction caused by certain intensive forest management practices can reduce tree growth, but the causes of growth reduction are usually complex interactions between soil properties and tree species. We used a 7 by 7 factorial greenhouse experiment to create a matrix of bulk density ((Ï b)) and volumetric water content (Î¸v) to determine soil compaction effects on seedling growth of: (i) ponderosa pine (Pinus ponderosa Dougl. ex Laws) grown on Dome and Cohasset soils from California; (ii) shortleaf pine (Pinus echinata) on a Clarksville soil from Missouri; and (iii) loblolly pine (Pinus taeda) on an Argent soil from South Carolina. We also characterized soil physical properties and determined compaction effects on soil strength, air/water balance and least limiting water range (LLWR) for each of the soils. Optimum water content for compaction varied from 19%(Argent) to 34%(Cohasset). Compactive effort curves varied for the four soils;maximum Ï b were 1.33, 1.52, 1.58 and 1.65 Mg m-3 for the Cohasset, Dome, Clarksville, and Argent soils, respectively. Compression indices ranged from 0.33 to 0.38. In general, soil strength increased linearly with a Î¸v decrease at the higher Ï b levels, but the effect varied with each soil type. Cohasset, with the lowest BD, had the highest soil strength (3.5 MPa), while strengths exceeding 2.0 MPa were not found for the Argent soil. Compaction affected the soil water retention curves and associated air/water balance parameters for all soils, particularly the Cohasset and Dome soils. Aeration porosity became limiting at Ï b of 1.3, 1.42, 1.44 and 1.55 Mg m-3 for the Cohasset, Dome, Clarksville and Argent soils respectively. The LLWR was lowest for the Dome and Argent soils (0.3 cm 3 cm-3 ) and in some cases increased with compaction. Models of root growth opportunity were developed using multiple regression. The general model of root length density (RLD) = b0 + b1 Î¸v + b2 Ï b + b3 Î¸v2 described rooting response for the Clarksville-shortleaf and Argent-loblolly soil-species combinations (p = 0.005). However, the root response of ponderosa pine on Cohasset was linear and pine roots in the Dome soil responded to an interaction between Î¸v and Ï b. No model adequately described oak seedling growth as a function of BD and VW. High soil strength at low water contents and low aeration porosity at high water contents limited root growth. Shoot mass of seedlings growing within the least limiting water range (LLWR) was greater than those growing outside the range for all soil-species combinations except the Argent-loblolly pine (p = 0.05). The loblolly pines had greater shoot mass at volumetric water contents above the upper LLWR limits (aeration limiting). The LLWR is a promising method for integrating compaction's influence on soil properties and thus root growth potential since single factors did not appear to adequately explain each soil's compressibility. Furthermore, response surface models of RLD as a function of VW and BD in conjunction with the LLWR and seasonal site water data have potential for determining compaction- induced soil limitations for tree growth, but need to be calibrated for both soil and species. Master of Science

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Thosago, Setshele Standford. "Response of selected cowpea lines to low soil phosphorus and moisture stress conditions at Ukulima Farm in Limpopo Province." Thesis, University of Limpopo, 2015. http://hdl.handle.net/10386/1585.

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Thesis (M. Sc.(Agronomy)) -- University of Limpopo, 2015 Cowpea (Vigna unguiculata L. Walp) is an important grain legume grown in many parts of the world mostly by smallholder (SH) farmers. Low soil phosphorus (P) and drought stress are major constraints to legume production and threaten food security. Root architecture is a spatial configuration of the root system which is influenced by moisture status and P uptake. A field experiment was conducted at Ukulima farm near Modimolle in Waterberg district during 2012/13 summer growing season. The treatments comprised of two levels each for soil P (low and high) and moisture status (water stress and well-watered); and eight cowpea genotypes (Tvu 4632, Tvu 6365, Tvu 9848, Tvu 15445, Tvu 16408, Tvu 15143, Oloyin and IT00K-1217). The low P level implied the available P in the soil measured in situ, which was less than 8 mg kg-1 while the high P level entailed fertilization at the rate of 40 kg P ha-1 application to achieve approximately 35 mg P kg-1 of soil . The root traits measured included angle of adventitious and basal roots, number of basal roots, tap root diameters at 5, 10, 15 and 20 cm soil depths; lateral branching densities at depth 5,10 and 15 cm, nodule score, deep score, shallowness score, 3rd order branching density, and 1.5 branching densities at 5 and 10 cm depth. Plant parameters measured were plant height, number of pods per plant, number of seeds per pod, length of the pods, unshelled weight, shelled weight and number of primary and secondary branches. Photosynthetic parameters measured were photosynthetic rate, intercellular CO2 concentration, water conductance, transpiration rate, vapour pressure deficits, sample cell CO2, sample cell H2O and relative humidity in the cell. All treatment factors were combined as split-split plot arrangement fitted into randomized complete block design; with four replicates. Results indicate that the lateral root branching density at 5 and 10 cm differed significantly (P≤0.05) across cowpea genotypes. Genotype showed significant effect on taproot diameter at 10 cm. Moisture status and P level exerted significant effect on cowpea genotypes 15 cm. There were significant differences (P≤0.05) for lateral root branching density observed at 5 and 10 cm depth in P rates x genotype interaction. Statistical analysis showed that P levels and cowpea genotypes had significant effects (P≤0.05) on mean plant height, biomass and highly significantly effects (P≤0.01) on number of branches, days to physiological maturity and mean pod length. The interaction between cowpea genotype and moisture stress condition significantly (P≤0.05) affected hundred (100) seed weight. Cowpea genotype Tvu16408 obtained highest grain yield of 3240 kg ha-1 and lowest was by IT00K1217 which obtained grain yield of 1256 kg ha-1. Results showed that photosynthetic rate, water conductance, transpiration rate, sample cell CO2, sample cell H2O, relative humidity in the cell, intercellular CO2 and vapour pressure deficit differed significantly (P≤0.05) across cowpea genotypes. Soil moisture condition and cowpea genotype exerted significant (P≤0.01) effect on photosynthetic rate, water conductance, transpiration rate, sample cell CO2, sample cell H2O and relative humidity in the cell. Variation in P levels had no significant effect on the measured photosynthetic parameters. Oloyin genotype had the highest photosynthetic rate followed by Tvu 4632 while cowpea genotype Tvu 9848 had the least photosynthetic rate. Interaction of moisture stress and cowpea genotype had a significant effect on intercellular CO2 concentration. Water stress reduced the intercellular CO2 concentration of Oloyin, Tvu 6365 and 4632 but resulted in a significant increase in intercellular CO2 concentration in Tvu 9848 genotype. Results showed that variation in soil P level exerted a significant (P≤0.05) effect on grain tissue P content and uptake, and a highly significant (P≤0.01) difference in P content across the various cowpea genotypes. Moisture stress exerted a significant (P≤0.05) difference on P uptake. The results showed that P levels and cowpea genotype variation exerted significant (P≤0.05) effects on P content, P uptake and nitrogen (N) uptake. Moisture status and cowpea genotype variation exerted significant (P≤0.05) effects on total N and N uptake. Cowpea genotype Tvu 9848 obtained more total N content (4.37%), while the lowest total N content was obtained by cowpea genotype Tvu 15445 with 3035 mg kg-1. The interaction between cowpea genotype and moisture status exerted a significant (P≤0.05) effect on N and P uptake of immature green pods harvested. There is a need to conduct more studies to identify cowpea genotypes, their root architecture and agronomic measures that can do well under xvii drought stress and low soil P conditions. Research needs to be conducted to enhance cowpea productivity under both low soil P and drought stress. Keywords: cowpea genotypes; moisture stress; phosphorus fertilisation; root traits

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Moffett, Jody E., William B. McCloskey, Stephen H. Husman, and Gary L. Dixon. "The Interaction and Effects of Soil Moisture Regime and Yellow Nutsedge (Cyperus esculentus) Density on Cotton (Gossypium hirsutum) Growth." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/210293.

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The goal of our research is to determine the effects of yellow nutsedge competition on cotton and to examine how the competitive relationship between these two species is modulated by soil moisture. In support of this goal, a competition experiment with various nutsedge densities and three irrigation regimes was conducted at the University of Arizona, Maricopa Agricultural Center. The results of this study indicate that increasing nutsedge density caused a significant linear decrease in cotton seed yield in both 1993 (p=0.03) and 1994 (p=0.002). The cotton yield reductions caused by the highest nutsedge densities, 33 and 50 tubers /m of crop row in 1993 and 1994, respectively, were 13.5 and 15.5 percent, respectively. Stem biomass, an indicator of total above ground biomass, increased significantly with increasing soil moisture. There was also a trend of increasing seed cotton yield with increasing soil moisture with the wet treatment (i.e., irrigation at 35 percent soil moisture depletion) resulting in the highest biomass and yields. In 1994 this trend was significant (p=0.0001) but in 1993 it was not (p=0.098) probably because fewer replications were used in 1993. An important goal of this research was to determine if cotton, with its deeper tap root type of root architecture, is more competitive against yellow nutsedge, which has a fibrous root system, when irrigation is less frequent. However, analysis of variance showed that there was no significant interaction between soil moisture availability and seed cotton yield reductions caused by nutsedge competition in either 1993 (p=0.44) or 1994 (p=0.62).

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20

Lee, Hock Seng, and n/a. "An ODE/MOL PDE Template For Soil Physics: A Numerical Study." Griffith University. Australian School of Environmental Studies, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030616.142709.

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The aim of the thesis is to find a method, in conjunction with the ordinary differential equation (ODE) based method of lines (MOL) solution of Richards equation, to model the steep wetting front infiltration in very dry soils, accurately and efficiently. Due to the steep pressure head or steep water volumetric content gradients, highly nonlinear soil hydraulic properties and the rapid movement of the wetting front, accurate solutions for infiltration into a dry soil are usually difficult to obtain. Additionally, such problems often require very small time steps and large computation times. As an enhancement to the used ODE/MOL approach, Higher Order Finite Differencing, Varying Order Finite Differencing, Vertical Scaling, Adaptive Schemes and Non-uniform Stretching Techniques have been implemented and tested in this thesis. Success has been found in the ability of Vertical Scaling to simulate very steep moving front solution for the Burgers equation. Unfortunately, the results also show that Vertical Scaling needs significant research and improvement before their full potential in routine applications for difficult nonlinear problems, such as Richards equation with very steep moving front solution, can be realized. However, we have also shown that the use of the composed form of RE and a 2nd order finite differencing for the first order derivative approximation is conducive for modelling steep moving front problem in a very dry soil. Additionally, with the combination of an optimal influx value at the edges of the inlet, the ODE/MOL approach is able to model a 2-D infiltration in very dry soils, effectively and accurately. Furthermore, one of the strengths of this thesis is the use of a MATLAB PDE template. Implementing the ODE/MOL approach via a MATLAB PDE template has shown to be most suitable for modelling of partial differential equations. The plug and play mode of modifying the PDE template for solving time-dependent partial differential equations is user-friendly and easy, as compared to more conventional approaches using Pascal, Fortran, C or C++. The template offers greater modularity, flexibility, versatility, and efficiency for solving PDE problems in both 1-D and 2-D spatial dimensions. Moreover, the 2-D PDE template has been extended for irregular shaped domains.

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Morgenroth, Justin. "The Effect of Porous Concrete Paving on Underlying Soil Conditions and Growth of Platanus orientalis." Thesis, University of Canterbury. School of Forestry, 2010. http://hdl.handle.net/10092/5112.

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Urbanisation is characterised by mass migration of people to urban areas and conversion of land from rural to urban land uses. Changes in population dynamics have led to half the world’s population living in urban areas; in developed countries, urban dwellers account for three-quarters of the total population. Though populations have shifted from rural to urban areas, people continue to rely on their environment, and trees in particular, for tangible and intangible benefits alike. A great deal of factual and anecdotal knowledge supports the role of trees for ecological, social, and economic well-being. In spite of this, during urbanisation, previously vegetated land is converted to housing, roads, or utility corridors, all of which are necessary to support growing populations. This thesis investigates tree growth in these modified urban landscapes, in particular, the effects of pavements on urban trees. Pavements are truly pervasive, covering more than half of all land in highly developed urban areas. Their durability and strength are of great importance to transportation, but large-scale soil sealing is not without consequence. Pavements affect the hydrologic cycle, soil and air temperature, and nutrient cycling. Because of their effect on the surrounding environment, pavements inherently affect remnant or planted trees. They are believed to negatively affect tree growth and survival, thereby compromising the ecological, social, and economic benefits otherwise derived from the urban forest. In recent times, porous pavements have been increasingly installed in favour of impervious pavements. Porous pavements are perceived to be an environmentally-sound alternative to standard impervious pavements. This thesis begins by reviewing the literature concerning porous pavement’s effect on underlying soil and urban vegetation, thus illustrating the scarcity of empirical data describing the effect of porous pavement on tree growth. A greater understanding of porous pavement’s impact on the surrounding environment is needed, if its installation is to continue. With this aim in mind, this thesis describes an experiment in Christchurch, New Zealand, which monitored the impacts of porous and impervious pavement on underlying soil conditions, and subsequent tree growth. The experiment comprised 50 Platanus orientalis trees planted in an augmented factorial design, which consisted of controls and four treatments. Trees were split evenly amongst plots, such that ten replicates existed per treatment. The pavement treatments measured 2.3m by 2.3m, and were based on the combination of pavement type (2 levels: porous, impervious) and pavement profile design (2 levels: +/- subbase compaction and gravel base). The resulting four treatments were impervious concrete pavement (IP), impervious concrete pavement with compacted subbase and gravel base (IP+), porous concrete pavement (PP), and porous concrete pavement with compacted subbase and gravel base (PP+). From December 2007 to March 2009, data were collected to determine the effect of these treatments on soil moisture, aeration, pH, and nutrient concentration. Final tree height, stem diameter, shoot and root biomass, and root distribution were also measured at the conclusion of the experiment. Results of this experiment indicated that the effects of pavement porosity on soil moisture and aeration were dynamic, varying with season and soil depth. Increased soil moisture beneath porous pavements resulted from rapid infiltration following precipitation. This decreased the duration of plant stress resulting from drought. Relative to bare soil, paved plots had consistently greater soil moisture, likely because pavements reduced evaporation. The inclusion of a gravel base in the profile design limited capillary upflow, which resulted in lower soil moisture under pavements designed with a gravel base. Soil aeration was significantly lower beneath pavements relative to unpaved plots. This is likely related to greater soil moisture beneath pavements. Finally, soil pH increased beneath pavements, in particular beneath porous pavements. Though all growth parameters increased for trees surrounded by porous, rather than impervious pavement, this occurred only in the absence of a compacted subgrade and gravel base. Evidently, the impact of the compacted subgrade superseded the impact of pavement porosity. Furthermore, root growth was relatively shallow beneath pavements, likely due to favourable soil moisture directly beneath pavements. This research highlights (i) the dramatic effect of pavements on underlying soil conditions; (ii) that pavements do not inherently limit tree growth; (iii) that porous pavements can conditionally improve tree growth; and (iv) that soil compaction limits potential benefits resulting from porous pavements.

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Drake, Arly Marie. "The Effect of Cultural Practices on the Surface Firmness of Putting Greens." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1398957202.

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Lloyd, Davidson A. "Effects of rhizosphere priming and microbial functions on soil carbon turnover." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9278.

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A major uncertainty in soil carbon studies is how inputs of fresh plant-derived carbon affect the turnover of existing soil organic matter (SOM) by so-called priming effects. Priming may occur directly as a result of nutrient mining by existing microbial communities, or indirectly via microbial population adjustments. Soil type and conditions may also influence the intensity and direction of priming effects. However the mechanisms are poorly understood. The objectives of this study were (1) to investigate how additions of labile C4 substrate affected SOM turnover in two contrasting unplanted C3 soils (clayey fertile from Temple Balsall, Warwickshire (TB) and sandy acid from Shuttleworth, Bedfordshire (SH) using13 C isotope shifts; (2) to investigate the influence of rhizodeposition from plant roots on SOM turnover in the same two soils planted with a C4 grass; (3) to assess an automated field system for measuring soil temperature, moisture and photosynthesis sensitivities of SOM turnover in the same two soils over diurnal to seasonal time scales. I used a combination of laboratory incubation, glasshouse and field experiments. In the soil incubation experiment, I made daily applications of either a maize root extract or sucrose to soil microcosms at rates simulating grassland rhizodeposition, and followed soil respiration (Rs) and its δ13 C over 19 days. I inferred the extent of priming from the δ13 C of Rs and the δ13 C of substrate and soil end-members. There were positive priming effects in both soils in response to the two substrates. In the SH soil there were no differences in priming effects between the substrates. However in the TB soil, sucrose produced greater priming effects than maize root extract, and priming effects with sucrose increased over time whereas with maize root extract declined after the first week. I explain these effects in terms of the greater fertility of the TB soil and resulting greater microbial nitrogen mineralization induced by priming. Because the maize root extract contained some nitrogen, over time microbial nitrogen requirements were satisfied without priming whereas with sucrose the nitrogen demand increased over time. In the glasshouse experiment, I planted C4 Kikuyu grass (Pennisetum clandestinum) in pots with the same two soils. The extent of rhizodeposition by the plants was altered by intermittently clipping the grass in half the pots (there were also unplanted controls) and priming effects were inferred from the δ13 C of Rs and the δ13 C of plant and soil end-members. Unclipped plants in both soils generated positive priming effects, while clipping reduced priming in TB soil and produced negligible PEs in SH soil. Microbial nutrient mining of SOM again explained the observed PEs in this experiment. Photosynthesis was a major driver of priming effects in the planted systems. In the third experiment, I found that the tested automated chamber system provided reliable measurements of Rs and net ecosystem exchange (NEE), and it was possible to draw relations for the dependency of Rs and NEE on key environmental drivers. Collectively, the results contribute to a better understanding of the mechanisms of priming effects and highlight possibilities for further research. The methods developed here will allow high temporal and spatial resolution measurements of Rs and NEE under field conditions, using stable isotope methods to separate fluxes into plant- and soil-derived components. Keywords: Soil respiration, soil moisture, soil temperature, Isotope ratio, maize root, flux chamber, climate change, organic matter, rhizodeposition.

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Brunke, Michael A., Patrick Broxton, Jon Pelletier, et al. "Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)." AMER METEOROLOGICAL SOC, 2016. http://hdl.handle.net/10150/612995.

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One of the recognized weaknesses of land surface models as used in weather and climate models is the assumption of constant soil thickness because of the lack of global estimates of bedrock depth. Using a 30-arc-s global dataset for the thickness of relatively porous, unconsolidated sediments over bedrock, spatial variation in soil thickness is included here in version 4.5 of the Community Land Model (CLM4.5). The number of soil layers for each grid cell is determined from the average soil depth for each 0.9 degrees latitude x 1.25 degrees longitude grid cell. The greatest changes in the simulation with variable soil thickness are to baseflow, with the annual minimum generally occurring earlier. Smaller changes are seen in latent heat flux and surface runoff primarily as a result of an increase in the annual cycle amplitude. These changes are related to soil moisture changes that are most substantial in locations with shallow bedrock. Total water storage (TWS) anomalies are not strongly affected over most river basins since most basins contain mostly deep soils, but TWS anomalies are substantially different for a river basin with more mountainous terrain. Additionally, the annual cycle in soil temperature is partially affected by including realistic soil thicknesses resulting from changes in the vertical profile of heat capacity and thermal conductivity. However, the largest changes to soil temperature are introduced by the soil moisture changes in the variable soil thickness simulation. This implementation of variable soil thickness represents a step forward in land surface model development.

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CHIMENTO, CARLO. "ASSESSMENT OF THE CARBON SEQUESTRATION POTENTIAL IN SOIL AND IN BELOWGROUND BIOMASS OF SIX PERENNIAL BIOMASS CROP." Doctoral thesis, Università Cattolica del Sacro Cuore, 2015. http://hdl.handle.net/10280/6072.

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L'obiettivo della ricerca è stato quello di identificare la coltura bioenergetica con il maggior potenziale di sequestro del carbonio (C); sono state considerate tre colture perenni arboree (pioppo, robinia e salice) e tre colture erbacee perenni (canna comune , miscanto e panico ) al sesto anno dal loro impianto e coltivate nello stesso ambiente. In primo luogo sono state misurate le variazioni dei tassi del C organico del suolo (COS) per il primo 1 m, mentre per i primi 30 cm di suolo è stato stimato il grado di stabilita del COS valutando sette frazioni di COS che presentano differenti gradi di stabilizzazione; in secondo luogo, sono stati caratterizzati gli apparati radicali delle sei specie per la stessa profondità di suolo, per valutare dove le specie accumulano la biomassa radicale lungo il profilo di suolo. I risultati confermano che l’impianto di colture bioenergetiche perenni su superfici precedentemente dedite a colture annuali gestite convenzionalmente rappresenta una opzione valida per sequestrare C nel soulo. Tuttavia, è stata osservata una diversa capacità di sequestro di C tra specie arboree ed erbacee: le specie arboree hanno dimostrato aumentre il contenuto di COS nel primo strato di suolo ( 0-10 cm di suolo), ma la loro capacità di allocare biomassa radicale negli strati profondi del suolo è limitata; mentre, la specie erbacee allocano un’alta quantità di biomassa radicale negli strati profondi del suolo, ma solo il panico ed il miscanto hanno aumentato il contenuto di C nel primo strato di suolo. The objective of the present research was to identify the bioenergy crop with the greatest carbon sequestration potential among three perennial woody crops (poplar, black locust and willow) and three perennial herbaceous crops (giant reed, miscanthus and switchgrass) at the sixth year from plantation and in the same location. First of all the SOC stock variations for the first 1 m soil depth and the quantification of seven soil C fractions related to SOC stabilization level of the first 30 cm of soil were assessed; secondly, a characterization of the root system and the traits which affect the carbon allocation in soil were considered. The results confirm that the establishment of perennial bioenergy crops in previous arable fields can be a suitable option to sequester carbon (C) belowground. However, a different C sequestration capacity was observed between woody and herbaceous crops: woody species showed the greatest SOC sequestration potential in the first soil layer (0-10 cm of soil) but their ability to allocate root biomass in the deeper soil layers was limited; while, the herbaceous species allocated a high amount of root biomass in the deeper soil layers, but only switchgrass and miscanthus sequester C in the first soil layer.

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26

CHIMENTO, CARLO. "ASSESSMENT OF THE CARBON SEQUESTRATION POTENTIAL IN SOIL AND IN BELOWGROUND BIOMASS OF SIX PERENNIAL BIOMASS CROP." Doctoral thesis, Università Cattolica del Sacro Cuore, 2015. http://hdl.handle.net/10280/6072.

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L'obiettivo della ricerca è stato quello di identificare la coltura bioenergetica con il maggior potenziale di sequestro del carbonio (C); sono state considerate tre colture perenni arboree (pioppo, robinia e salice) e tre colture erbacee perenni (canna comune , miscanto e panico ) al sesto anno dal loro impianto e coltivate nello stesso ambiente. In primo luogo sono state misurate le variazioni dei tassi del C organico del suolo (COS) per il primo 1 m, mentre per i primi 30 cm di suolo è stato stimato il grado di stabilita del COS valutando sette frazioni di COS che presentano differenti gradi di stabilizzazione; in secondo luogo, sono stati caratterizzati gli apparati radicali delle sei specie per la stessa profondità di suolo, per valutare dove le specie accumulano la biomassa radicale lungo il profilo di suolo. I risultati confermano che l’impianto di colture bioenergetiche perenni su superfici precedentemente dedite a colture annuali gestite convenzionalmente rappresenta una opzione valida per sequestrare C nel soulo. Tuttavia, è stata osservata una diversa capacità di sequestro di C tra specie arboree ed erbacee: le specie arboree hanno dimostrato aumentre il contenuto di COS nel primo strato di suolo ( 0-10 cm di suolo), ma la loro capacità di allocare biomassa radicale negli strati profondi del suolo è limitata; mentre, la specie erbacee allocano un’alta quantità di biomassa radicale negli strati profondi del suolo, ma solo il panico ed il miscanto hanno aumentato il contenuto di C nel primo strato di suolo. The objective of the present research was to identify the bioenergy crop with the greatest carbon sequestration potential among three perennial woody crops (poplar, black locust and willow) and three perennial herbaceous crops (giant reed, miscanthus and switchgrass) at the sixth year from plantation and in the same location. First of all the SOC stock variations for the first 1 m soil depth and the quantification of seven soil C fractions related to SOC stabilization level of the first 30 cm of soil were assessed; secondly, a characterization of the root system and the traits which affect the carbon allocation in soil were considered. The results confirm that the establishment of perennial bioenergy crops in previous arable fields can be a suitable option to sequester carbon (C) belowground. However, a different C sequestration capacity was observed between woody and herbaceous crops: woody species showed the greatest SOC sequestration potential in the first soil layer (0-10 cm of soil) but their ability to allocate root biomass in the deeper soil layers was limited; while, the herbaceous species allocated a high amount of root biomass in the deeper soil layers, but only switchgrass and miscanthus sequester C in the first soil layer.

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27

Nyalemegbe, Kenneth K. "Growth, nodulation and nitrogen fixation of the faba bean (Vicia faba L.) under contrasting soil moisture conditions and under varied crop density and shading." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240164.

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Cline, Nathan Lyle. "Wet-Thermal Time and Plant Available Water in the Seedbeds and Root Zones Across the Sagebrush Steppe Ecosystem of the Great Basin." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4384.

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Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature conditions. In an effort to help improve plant materials selection and to evaluate sites potential revegetation, we have worked toward developing methodology to predict germination and root growth based on site specific soil moisture and temperature conditions. First, we characterized the seedbed environment of 24 sagebrush (Artemisia spp.) steppe sites throughout the Intermountain West to determine the wet-thermal time of five temperature ranges relevant to germination response and thermal-time model accuracy (Chapter 1). Second, we predicted potential germination for 31 plant materials at those same sites (Chapter 2). Third, in preparation to predict root growth at multiple sites, we characterized the drying patterns and the associated plant-available water for in the seedling root zone across nine woodland (Juniperus spp. and Piñus spp.) sites (Chapter 3). For all of these studies, we determined the effects of tree reduction and tree infilling phase at time of tree reduction. Our key findings are that seedbeds generally sum most wet-thermal time at temperature ranges where the germination rates fit thermal accumulation models quite well (R2 ≥ 0.7). The majority of plant materials summed enough wet-thermal time for a potential germination at most sites during the fall, early spring, and late spring. Soil drying primarily occurs from the soil surface downward. Drying rates and Plant available water associated with the first drying event increased with increasing soil depth. Root zone (1-30 cm) plant-available water increased before and decreased after the first spring drying event with increasing soil depth. Tree removal with increasing pretreatment tree infilling phase generally added progress toward germination, plant available water, and wet-thermal time in the seedbed and root zones of the sagebrush steppe in the Great Basin. Because soil moisture and temperature does not appear to be limiting for potential germination, combining germination and root growth models to create a more comprehensive model may allow for a more robust prediction for seedling survival. For either root growth or combined germination and root growth models, plant available water and wet-thermal time before the first spring drying period hold the most potential for successfully predicting seedling survival.

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Kusumo, Bambang Hari. "Development of field techniques to predict soil carbon, soil nitrogen and root density from soil spectral reflectance : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1015.

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The objectives of this research were to develop and evaluate a field method for in situ measurement of soil properties using visible near-infrared reflectance spectroscopy (Vis-NIRS). A probe with an independent light source for acquiring soil reflectance spectra from soil cores was developed around an existing portable field spectrometer (ASD FieldSpecPro, Boulder, CO, USA; 350-2500 nm). Initial experiments tested the ability of the acquired spectra to predict plant root density, an important property in soil carbon dynamics. Reflectance spectra were acquired from soil containing ryegrass roots (Lolium multiflorum) grown in Allophanic and Fluvial Recent soils in a glasshouse pot trial. Differences in root density were created by differential nitrogen and phosphorus fertilization. Partial least squares regression (PLSR) was used to calibrate spectral data (pre-processed by smoothing and transforming spectra to the first derivative) against laboratory-measured root density data (wet-sieve technique). The calibration model successfully predicted root densities (r2 = 0.85, RPD = 2.63, RMSECV = 0.47 mg cm-3) observed in the pots to a moderate level of accuracy. This soil reflectance probe was then tested using a soil coring system to acquire reflectance spectra from two soils under pasture (0-60 mm soil depths) that had contrasting root densities. The PLSR calibration models for predicting root density were more accurate when soil samples from the two soils were separated rather than grouped. A more accurate prediction was found in Allophanic soils (r2 = 0.83, RPD = 2.44, RMSECV = 1.96 mg g-1) than in Fluvial Recent soils (r2 = 0.75, RPD = 1.98, RMSECV = 5.11 mg g-1). The Vis-NIRS technique was then modified slightly to work on a soil corer that could be used to measure root contents from deeper soil profiles (15- 600 mm depth) in arable land (90-day-old maize crop grown in Fluvial Recent soils). PLSR calibration models were constructed to predict the full range of maize root densities (r2 = 0.83, RPD = 2.42, RMSECV = 1.21 mg cm-3) and also soil carbon (C) and nitrogen (N) concentrations that had been determined in the laboratory (LECO FP- 2000 CNS Analyser; Leco Corp., St Joseph, MI, USA). Further studies concentrated on improving the Vis-NIRS technique for prediction of total C and N concentrations in differing soil types within different soil orders in the field. The soil coring method used in the maize studies was evaluated in permanent and recent pastoral soils (Pumice, Allophanic and Tephric Recent in the Taupo-Rotorua Volcanic Zone, North Island) with a wide range of soil organic matter contents resulting from different times (1-5 years) since conversion from forest soils. Without any sample preparation, other than the soil surface left after coring, it was possible to predict soil C and N concentrations with moderate success (C prediction r2 = 0.75, RMSEP = 1.23%, RPD = 1.97; N prediction r2 = 0.80, RMSEP = 0.10%, RPD = 2.15) using a technique of acquiring soil reflectance spectra from the horizontal cross-section of a soil core (H method). The soil probe was then modified to acquire spectra from the curved vertical wall of a soil core (V method), allowing the spectrometer’s field of view to increase to record the reflectance features of the whole soil sample taken for laboratory analysis. Improved predictions of soil C and N concentrations were achieved with the V method of spectral acquisition (C prediction r2 = 0.97, RMSECV = 0.21%, RPD = 5.80; N prediction r2 = 0.96, RMSECV = 0.02%, RPD = 5.17) compared to the H method (C prediction r2 = 0.95, RMSECV = 0.27%, RPD = 4.45; N prediction r2 = 0.94, RMSECV = 0.03%, RPD = 4.25). The V method was tested for temporal robustness by assessing its ability to predict soil C and N concentrations of Fluvial Recent soils under permanent pasture in different seasons. When principal component analysis (PCA) was used to ensure that the spectral dimensions (which were responsive to water content) of the data set used for developing the PLSR calibration model embraced those of the “unknown” soil samples, it was possible to predict soil C and N concentrations in “unknown” samples of widely different water contents (in May and November), with a high level of accuracy (C prediction r2 = 0.97, RMSEP = 0.36%, RPD = 3.43; N prediction r2 = 0.95, RMSEP = 0.03%, RPD = 3.44). This study indicates that Vis-NIRS has considerable potential for rapid in situ assessment of soil C, N and root density. The results demonstrate that field root densities in pastoral and arable soil can be predicted independently from total soil C, which will allow researchers to predict C sequestration from root production. The recommended “V” technique can be used to assess spatial and temporal variability of soil carbon and nitrogen within soil profiles and across the landscape. It can also be used to assess the rate of C sequestration and organic matter synthesis via root density prediction. It reduces the time, labour and cost of conventional soil analysis and root density measurement.

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Sun, Hongwei. "The effect of seaweed concentrate on turfgrass growth, nematode tolerance and protein synthesis under moisture stress conditions." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-163430/.

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31

Klinka, Karel. "The association between western hemlock fine roots and woody versus non-woody forest floor substrates in coastal British Columbia." Forest Sciences Department, University of British Columbia, 2001. http://hdl.handle.net/2429/664.

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In the wetter climates associated with the coastal forests of the Pacific Northwest, coarse woody debris (CWD) accumulations in the form of snags, downed boles, and large branches can be large in natural forest ecosystems. Although maintaining organic matter for sustainable site productivity is not in dispute, the importance of CWD as a source of soil organic matter is questionable. Forest managers attempting to optimize timber production need to know how CWD affects short-term forest tree growth and productivity. This study addresses the question of the immediate value of CWD for growth of mature (90 year old) western hemlock (Hw). Because of practical difficulty with mature trees growing in different substrates, we utilized fine root distribution or proliferation, as an indicator of important substrates.

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Falkenberg, Nyland Ray. "Remote sensing for site-specific management of biotic and abiotic stress in cotton." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/478.

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This study evaluated the applicability of remote sensing instrumentation for site- specific management of abiotic and biotic stress on cotton grown under a center pivot. Three different irrigation regimes (100%, 75%, and 50% ETc) were imposed on a cotton field to 1) monitor canopy temperatures of cotton with infrared thermometers (IRTs) in order to pinpoint areas of biotic and abiotic stress, 2) compare aerial infrared photography to IRTs mounted on center pivots to correlate areas of biotic and abiotic stress, and 3) relate yield to canopy temperatures. Pivot-mounted IRTs and IR camera were able to differentiate water stress between the irrigation regimes, however, only the IR camera was effectively able to distinguish between biotic (cotton root rot) and abiotic (drought) stress with the assistance of groundtruthing. The 50% ETc regime had significantly higher canopy temperatures, which were reflected in significantly lower lint yields when compared to the 75% and 100% ETc regimes. Deficit irrigation up to 75% ETc had no impact on yield, indicating that water savings were possible without yield depletion.

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Vanella, Daniela. "Monitoring and modeling fluxes transfer processes in soil-plant-atmosphere continuum across scales." Doctoral thesis, Università di Catania, 2017. http://hdl.handle.net/10761/4084.

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Alle interazioni tra le diverse componenti del sistema suolo-pianta-atmosfera (SPA) è attribuito un ruolo critico nel ciclo idrologico e della biosfera terrestre. La comunità scientifica specializzata è sempre più consapevole della necessità di portare avanti studi a carattere interdisciplinare per la comprensione delle interazioni funzionali tra le risorse naturali ed i relativi problemi di sostenibilità del sistema SPA. All interno di tali studi interdisciplinari, l analisi delle interazioni suolo-radice risulta rilevante anche per la gestione ottimale dell'irrigazione, in particolare nelle zone caratterizzate da scarsa disponibilità idrica, come le aree mediterranee. A tal fine nasce l esigenza di valutare, ad alta risoluzione sia spaziale che temporale, le dinamiche idrologiche del sistema SPA, sino alla scala dell apparato radicale. Il contributo della tesi di dottorato consiste nell applicazione di tecniche di monitoraggio avanzate e minimamente invasive, per valutare gli scambi di massa ed energia all'interno del sistema SPA. L aspetto innovativo del lavoro di tesi consiste nell integrazione di tecniche geofisiche con misure micrometeorologiche e dati di traspirazione, al fine di interpretare alcuni dei principali processi di trasferimento di flussi nel sistema SPA (evapotraspirazione ed assorbimento radicale) in ambiente semi-arido. Tale approccio, è stato applicato a due Casi studio con l obiettivo di monitorare le complesse interazioni del sistema suolo-pianta, con particolare riferimento al processo di assorbimento radicale di alberi di agrume. Nel primo Caso studio, la tecnica della tomografia di resistività elettrica (ERT) tridimensionale è stata integrata con dati di traspirazione, misure micrometeorologiche e modellistica idrologica al fine di delineare la porzione di suolo non satura interessata dalle radici attive di un aranceto adulto. Nel secondo Caso studio, il monitoraggio ERT è stato integrato con misure di traspirazione al fine di delineare i pattern di RWU di alberi di arancio irrigati in regime di deficit. I risultati del lavoro di tesi dimostrano l abilità della tecnica di monitoraggio geofisico ERT nello spiegare le dinamiche idriche del suolo e la risposta fisiologica della pianta, in termini di attività delle radici nel processo di uptake, contribuendo, in tal senso, a migliorare la conoscenza dei processi di assorbimento radicale.

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Szota, Christopher. "Root morphology, photosynthesis, water relations and development of jarrah (Eucalyptus marginata) in response to soil constraints at restores bauxite mines in south-western Australia." University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2010.0058.

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Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.

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35

Rupollo, Carlos Zandoná. "Avaliação físico-hídrica de um latossolo vermelho em pastagem de jiggs manejada sob diferentes intensidades de pastejo." Universidade Federal de Santa Maria, 2016. http://repositorio.ufsm.br/handle/1/5623.

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Perennial summer pastures are an excellent forage option for livestock feed, a fact that has boosted milk production in Rio Grande do Sul. However, the lack of animal load control coupled with high grazing intensities have contributed to the degradation of pastures and loss of soil quality. The study was conducted on a farm in northern Rio Grande do Sul, and the forage used was Jiggs (Cynodon dactylon) and management method adopted was the rotational grazing, covering a 268 days production cycle. The treatments consisted of different grazing intensities in a randomized block design with four replications which the following treatments were: T1 = intensity of 0%, T2 = 30%, T3 and T4 = 50% = 70%. The experimental area was disposed within a total area of 1,760 m2, which were distributed pickets 16 (4 treatments x 4 replicates) with dimensions equal to 100 m2 each (10 x 10 m). The production of forage Jiggs had no statistical difference among treatments and the production decreases with the end of the production cycle, however, the highest concentration of leaves was found at the end of the grazing cycle influenced by plant height. There is a reduction with respect to the length and root density with increasing soil depth and the treatment one where grazing intensity was zero, had the lowest average density with respect to other treatments. The air permeability of the soil (Kar) equilibrated to tensions of 6 and 100 kPa did not reach statistical difference between treatments and the depth in the periods pre and post grazing 1. The soil layer of 0-5 and 5-10 cm was that the only influenced by the treatments in Ksat, Kar and 6 and 100 kPa, leading to a reduction in the flow of air and water in the grazing periods post 3 is 5. The grazing intensity significantly alter the soil density and macroporosity and total porosity in the 0-5 and 5-10 cm. The T1 had increasing density mean values with increasing depth, however, the treatment had decreasing average values obtained in the course of depths, where the 0-5 cm layer obtained density 1.49 g cm-3. During the grazing cycle was observed generally that the microporosity remained virtually constant. The forage production showed no statistical difference in relation to grazing intensity, the roots are concentrated in the 0-5 cm layer and cattle trampling influenced root density. In general, the grazing periods influenced Kar, Ksat and bulk density in the surface layers of the soil and the micro, macro and total porosity were mainly influenced by grazing period post 3 and post 5. As pastagens perenes de verão surgem como uma excelente opção de forrageira para alimentação do gado, fato esse que tem impulsionado a produção de leite no Rio Grande do Sul. Todavia, a falta de controle da carga animal aliada a intensidades de pastejo elevada tem contribuído com a degradação das pastagens e perda da qualidade do solo. O estudo foi desenvolvido numa propriedade rural no norte gaúcho, sendo que a forrageira utilizada foi o Jiggs (Cynodon dactylon) e o método de manejo adotado foi o pastejo rotacionado, contemplando um ciclo de produção de 268 dias. Os tratamentos foram compostos de distintas intensidades de pastejo em blocos ao acaso e contaram com quatro repetições as quais constituíram os seguintes tratamentos: T1= intensidade de 0%, T2= 30%, T3= 50% e T4= 70%. A área experimental estava disposta dentro de uma área total de 1.760 m2, onde foram distribuídos 16 piquetes (4 tratamentos x 4 repetições) com dimensões iguais a 100 m2 cada (10 x 10 m). A produção da forrageira Jiggs não apresentou diferença estatística com relação aos tratamentos, sendo que a produção decresce com o fim do ciclo produtivo, em contrapartida, a maior concentração de folhas foi encontrada no fim do ciclo de pastejo influenciada pela altura das plantas. Ocorreu redução com relação ao comprimento e densidade de raiz com aumento da profundidade sendo que a intensidade de pastejo igual a zero, apresentou a menor densidade média com relação as demais intensidades. A permeabilidade do solo ao ar (Kar) equilibrado à tensões de 6 e 100 kPa não obteve diferença estatística entre as intensidades de pastejo e a profundidade nos períodos de Pré Pastejo e no Pós Pastejo 1. A camada de solo de 0-5 e 5-10 cm foi a única que sofreu influencia dos tratamentos na Ksat e Kar à tesões de 6 e 100 kPa, ocorrendo redução do fluxo de ar e água nos períodos de pastejo Pós 3 e 5. A intensidade de pastejo altera significativamente a densidade de solo bem como a macroporosidade e porosidade total nas camadas de 0-5 e de 5-10 cm. a intensidade de 0% obteve valores médios crescentes de densidade conforme o aumento da profundidade, no entanto, o tratamento 4 obteve valores médios decrescentes no decorrer das profundidades, onde a camada de 0-5 cm apresentou densidade de 1,49 g cm-3. No decorrer do ciclo de pastejo, observou-se de modo geral que a microporosidade manteve-se praticamente constante. Em síntese, a produção de forragem não apresentou diferença estatística com relação às intensidades de pastejo, as raízes se concentram na camada de 0-5 cm e o pisoteio animal influencia na densidade de raiz. De modo geral, os períodos de pastejo influenciaram a Kar, Ksat e densidade do solo nas camadas superficiais do solo e a micro, macro e porosidade total foram influenciadas principalmente pelos períodos de pastejo Pós 3 e 5.

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36

Eastman, Christopher Mark. "Soil Physical Characteristics of an Aeric Ochraqualf amended with Biochar." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316548127.

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37

Akgul, Alper. "Performance of slash pine (Pinus elliottii Engelm.) containerized rooted cuttings and bare-root seedlings established on five planting dates in the flatlands of western Louisiana." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2230.

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The forest product industry is keenly interested in extending the normal planting season, as well as in the comparative field performance of standard nursery bare-root seedlings and containerized rooted cuttings. The effect of seasonal planting dates on survival, above and belowground biomass allocation, water relations, gas exchange attributes and foliar carbon isotope composition (δ13C) of two stock types of slash pine (Pinus elliottii Engelm.) were examined. Slash pine bare-root seedlings (BRS) and containerized rooted cuttings (CRC) were hand planted in September, November, January, March and April in three consecutive planting seasons (2000-2001, 2001-2002 and 2002-2003) on three sites with silt loam topsoils in southwestern Louisiana. First-year mean survival of CRC across all planting dates and sites was consistently high at 96 to 98%, whereas BRS survival was significantly (P < 0.0001) lower at 59 to 81% and highly variable among study sites and dates through three planting seasons. Generally, there was a negative relationship between soil moisture at the time of planting and first-year survival of BRS planted September through March in 2001-2002 and 2002-2003 planting seasons, whereas the opposite was observed only for BRS planted in April 2002 and 2003. Survival of CRC was affected very little by the variation in soil moisture. Containerized rooted cuttings had higher early above and belowground biomass, and height and diameter than did BRS. However, three years after planting the size differences between stock types disappeared or became negligible. Early size differences among trees planted September through March also decreased after three years, although September trees were tallest. Growth of the April-planted trees was poor compared to trees planted in other months. Late-planted April trees had higher δ13C values, and higher water-use efficiency in the first growing season compared to earlier planted trees. Differences in δ13C values among the planting dates disappeared in the second growing season. Net photosynthesis rates did not differ considerably between stock types or among planting dates in the second and third growing seasons. This study indicates that it is possible to extend the planting season to as early as September and as late as March by using CRC.

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38

Juhász, Carlos Eduardo Pinto. "Relação solo-água-vegetação em uma toposseqüência localizada na Estação Ecológica de Assis, SP." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-17042006-163701/.

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O bioma Cerrado está cada vez mais fragmentado devido à ocupação agrícola e antrópica. Para a manutenção da biodiversidade, corredores de vegetação devem ser criados com o auxílio da revegetação e recuperação de áreas degradadas. Isto é facilitado pelo conhecimento da distribuição e dinâmica natural dos solos. O objetivo deste trabalho foi caracterizar o funcionamento físico-hídrico dos solos distribuídos em uma toposseqüência sob vegetação nativa. A área de estudo foi localizada dentro de uma parcela permanente instalada na Estação Ecológica de Assis, SP, Brasil, com vegetação predominante de cerradão ou savana florestada. Para a caracterização do funcionamento físico-hídrico dos solos foram realizados inicialmente estudos morfológicos, a partir da técnica da análise estrutural e da descrição de perfis de solo dispostos em cinco posições-chave da encosta. Amostras deformadas de solo foram utilizadas em análises químicas, granulométricas e densidade de partículas. Amostras indeformadas coletadas em anéis cilíndricos definiram as curvas de retenção de água e a densidade do solo. Blocos de solo foram impregnados e polidos para análise de imagens, obtendo-se a distribuição de poros em número, forma e tamanho. Em poços perfurados em três setores da toposseqüência, foi determinada a condutividade hidráulica saturada de campo. O monitoramento da umidade do solo in situ foi obtido por sensores instalados nos principais horizontes das trincheiras, calibrados para cada horizonte, durante o período de novembro de 2003 a novembro de 2004. Foram também utilizados os dados de precipitação mais próximos. Fotografias digitais adquiridas nos perfis de solo determinaram a distribuição das raízes. Os solos foram classificados, de montante a jusante, em Latossolo Vermelho, Latossolo Vermelho-Amarelo, Latossolo Amarelo e Gleissolo Háplico, com transição homogênea de cor e predomínio de textura franco-arenosa. No horizonte de superfície da toposseqüência, pequeno número de poros complexos de diâmetro equivalente superior a 1000µm ocupou quase a área total da imagem, representando uma estrutura de empilhamento de grãos simples com porosidade maior que em profundidade. Este comportamento provocou uma menor retenção hídrica, apesar do maior teor de matéria orgânica, e oscilação da umidade do solo após cada evento chuvoso. Predominaram raízes aglomeradas ou ramificadas nesta camada. Em profundidade, as raízes são mais individuais. Nos Latossolos, maior número de poros complexos de diâmetro equivalente superior a 1000 µm ocupa menor área em Bw do que em superfície. Isto indica a presença de aglomerados de microagregados em Bw que conferem maior retenção de água, maior número de microporos e menor oscilação da umidade do solo do que em superfície. No Gleissolo, o horizonte Btg2, mais profundo e mais argiloso, apresentou estrutura mais densa representada por uma porosidade expressiva de forma arredondada ou cavitária de diâmetro de 30 a 1000 µm. Neste horizonte, foi obtida a maior retenção hídrica, drenagem imperfeita e menor condutividade hidráulica. Nos outros horizontes da toposseqüência a condutividade foi elevada. O relevo influenciou nas propriedades físicohídricas e morfológicas dos solos que, por sua vez, determinaram o conteúdo de água limitante na estação seca e em períodos de estiagem. Este comportamento pode definir o padrão florístico de cerradão na parcela permanente. The Cerrado bioma is being fragmented due to the human and agricultural occupation. To maintain the biodiversity, ecological corridors must be created by the revegetation and the restoration of the degraded areas. It can only be ameliorated upon the knowledge of the soils natural dynamics and distribution. The aim of this work was to characterize the behavior of soil water flow and soil physical properties, distributed in a toposequence under native vegetation. The study area was in a permanent plot installed in the Assis Ecological Station, São Paulo, Brazil. The predominant vegetation is the closed cerrado or savanna woodland. The soil physical, hydraulic characterization depended on soil morphology. The morphological study was carried out by structural analysis and by description of soil profiles arranged in five key positions on the slope. Disturbed soil samples were taken for chemical, particle size and soil particle density analyses. Undisturbed samples collected in cylindrical cores were used to define the soil water retention and bulk density. Soil blocks were impregnated and polished for image analysis to obtain the distribution of pores in number, shape and size. In wells perforated in three sectors of the toposequence the field saturated hydraulic conductivity was determined. The soil moisture monitoring in situ was obtained by sensors installed in the main horizons of the pits and calibrated for each soil horizon, during the period of November 2003 to November 2004. The nearest rain volume data were collected too. Digital photos of the soil profiles were acquired for the determination of the root distribution. The soils were classified, from the top backslope down to the footslope, as Rhodic Haplustox, Typic Haplustox and Epiaquic Haplustult, with a homogeneous color transition and the predominance of a sandy loam texture. In the soil surface on the toposequence, a little number of complex pores with equivalent diameter over 1,000 µm occupied almost the total pore area, characterizing the predominance of a structure formed by the packing of single grains. The porosity was higher than in the other horizons. This behavior caused lower water retention even with the highest organic matter content. On the surface, the oscillation of the soil moisture is closely related to each rain event. The roots were distributed in ramified or grouped roots in the surface layer and individually in the deeper horizons. In Oxisols, the presence of microaggregates in the B-horizon was characterized by a number of complex pores with equivalent diameter over 1,000 µm larger than in the soil surface but in minor area than in the surface layer. This conferred higher water retention, larger number of micropores and lower oscillation of soil moisture than in soil surface. The structure of the deepest B-horizon of Epiaquic Haplustult was denser, featured by an expressive rounded or vugh porosity with diameters between 30 and 1,000 µm. This conferred the largest content of clay, with the highest water retention, imperfect drainage and lowest hydraulic conductivity. The other soil horizons in the toposequence presented greater hydraulic conductivity. The landscape influences the physical, hydraulic and morphological soil properties in the toposequence. So the water content is limited in the dry season and partially in the humid season too, which can define the floristic pattern of the closed cerrado in this permanent plot.

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Čermák, Petr. "Použití programu Rosetta k odhadu retenčních čar půdní vlhkosti z experimentální plochy Bohaté Málkovice." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227176.

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Hydraulic characteristics are the most important properties of soil, i.e. retention curve of soil moisture and hydraulic conductivity. Hydraulic conductivity of soil characterizes the ability of the soil to conduct water. Retention curve expresses the relationship between moisture and moisture potential of soil. The running of retention curve is influenced by many factors, eg. grain size and mineralogical composition, content of humus, reduce bulk density and structure of soil. Measurement of retention curves takes a lot of time and money in laboratory conditions therefore pedotransfer functions seem to be an alternative solution. The thesis aims to estimate moisture retention curves of soil in a selected area of interest in South Moravia using program Rosetta (Schaap, 2003). Data of granularity (% content of clay, sand and dust), bulk density of soil and hydrolimits field water capacity and wilting point were used as predictors in individual models of program Rosetta. Data of grain were matched by FAO / USDA system. Retention curves of soil moisture were measured on a sand tank and overpressure devices. The measured retention curves were parameterized by RETC program. Estimated retention curves were graphically compared with measured to determine the quality of the estimate. The accuracy of the estimate was assessed by correlation coefficient R of determination coefficient R2 and standard error SMRE. Usability own derivatives pedotransfer functions is hard to say due to the size of the input data file. I would recommend further verification of data at the other localities in south Moravia.

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40

Mauritsson, Karl. "Ecological and Edaphic Correlations of Soil Invertebrate Community Structure in Dry Upland Forests of Eastern Africa." Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-15369.

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Natural forests are characterised by great vegetation diversity and create habitats for a major part of Earth’s terrestrial organisms. Plantation forests, which are mainly composed of a few genera of fast-growing trees, constitute an increasing fraction of global forests, but they only partly compensate for loss of area, habitat and ecological functions in natural forests. Plantation forests established near natural forests can be expected to serve as buffers, but they seem to be relatively poor in invertebrate species and it is not clear why. This bachelor’s degree project aimed at establishing the ecological and edaphic factors that correlate with soil invertebrate diversity in dry upland forests and surrounding plantation forests in eastern Africa. Some aspects of the above-ground vegetation heterogeneity were investigated since this was assumed to influence the heterogeneity of the soil environment, which is considered as critical for soil biodiversity. The obtained knowledge may be valuable in conservation activities in East African forests, which are threatened by destruction, fragmentation and exotic species. The study area was Karura Forest, a dry upland forest in Nairobi, Kenya. Three different sites were investigated; a natural forest site characterized by the indigenous tree species Brachylaena huillensis and Croton megalocarpus, and two different plantation forest sites, characterized by the exotic species Cupressus lusitanica and Eucalyptus paniculata, respectively. For each forest type, six plots were visited. Soil invertebrates were extracted from collected soil and litter samples by sieving and Berlese-Tullgren funnels. The invertebrates were identified, and the taxonomic diversity calculated at the order level. The ecological and edaphic factors, measured or calculated for each plot, were tree species diversity, ratio of exotic tree species, vertical structure of trees, vegetation cover, vegetation density, litter quality, soil pH, soil temperature and soil moisture. One-way ANOVA was used to compare soil invertebrate diversity and other variables between different forest types. Akaike’s Information Criterion and Multiple Linear Regression were used to establish linear models with variables that could explain measured variations of the diversity. There was some evidence for higher soil invertebrate diversity in natural forests than in surrounding plantation forests. The abundance of soil invertebrates was also clearly higher in natural forests, which indicates that natural forests are more important than plantation forests for conservation of soil invertebrate populations. Soil invertebrate diversity (in terms of number of orders present) was found to be influenced by forest type and litter quality. The diversity was higher at places with high amounts of coarse litter, which here is considered as more heterogenous than fine litter. The dependence on forest type was partly a consequence of differences in soil pH since Eucalyptus trees lower soil pH and thereby also soil biodiversity. No relation to heterogeneity of above-ground vegetation was found. For future conservation activities in Karura Forest Reserve it is recommended to continue removing exotic plant species and replanting indigenous trees, to prioritize the removal of Eucalyptus trees before Cypress trees, to only remove a few trees at a time and to establish ground vegetation when doing so.

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Veiga, Milton da. "Propriedade de um nitossolo vermelho após nove anos de uso de sistemas de manejo e efeito sobre culturas." Universidade Federal de Santa Maria, 2005. http://repositorio.ufsm.br/handle/1/3351.

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Long-term use of management systems result in alteration in physical and chemical soil properties and its intensity is related to time, soil and climate conditions. Physical properties are more susceptible to changes by the tillage system, while chemical properties by the residue management and nutrient application, resulting in different responses of crops growth and yield. This study was performed in order to evaluate long-term effect of applying soil tillage systems (NT = no-till; CP = chisel plow + 1 secondary disking; CT = primary + 2 secondary disking; CTb = CT with crop residues burned; and CTr = CT with crop residues removed from the field) and nutrient sources (C = control, without nutrient application; MF = mineral fertilizers according official recommendation for each crop; PL = 5 Mg ha-1 of wet matter of poultry litter; CM = 60 m3 ha-1 of liquid cattle manure; and SM = 40 m3 ha-1 of liquid swine manure) on soil properties and crop production. Soil physical and hydraulic properties and aggregate stability were evaluated at the end of ninth year of the experiment and in five sampling times throughout the tenth year; soil mechanical properties related to soil strength and penetration resistance were determined for some treatments combinations in the tenth year; soil cover, temperature and moisture were determined throughout corn cycle in 2003/2004 crop season, when corn growth and yield were also measured. No-till showed greater bulk density and lower macroporosity and total porosity after tillage and seeding operations, but the differences reduced over time. All tillage systems showed higher compaction degree at depth around 15 cm. Greater mean diameter of air-dry aggregates were found in tillage treatments and layers with higher bulk density, showing close relation between these two parameters. Wet-aggregate stability, on the other hand, was affected by aggregate moisture previous to wet-sieving determination, and greater values were found in tillage treatments where residues were kept in the field. At superficial layer of no-till was observed higher soil strength, as determined by the precompression stress, and to penetration resistance in untrafficked interrow. In seeding row and recent trafficked interrow the differences in penetration resistance among tillage systems were smaller. Higher soil temperature and daily amplitude were found in tilled treatments, mainly at the beginning of corn cycle. After rainfall events, soil moisture reduced faster in chisel plow system, followed by conventional tillage. Higher moisture content and lower water tension was found in no-till system even in long period with hydric deficits, resulting in higher water storage and availability to crops. Higher water availability seems to be the main factor in determining higher crop growth and yield in no-till treatment. Nutrient sources treatments had small effect on physical soil properties, but high effect on chemical properties and crop growth and yield. Greater growth and yield were observed with poultry litter and swine manure application, because of residual and immediate effect of nutrient application through these materials. A utilização continuada de diferentes sistemas de manejo determina alterações nas propriedades físicas e químicas do solo, cuja intensidade depende do tempo de uso e das condições edafoclimáticas. As propriedades físicas são mais afetadas pelos sistemas de preparo enquanto que as propriedades químicas pelo manejo dos resíduos das culturas e pela aplicação de nutrientes, resultando em respostas diferenciadas em termos de crescimento e produção das culturas. O efeito de sistemas de manejo sobre as propriedades do solo e produção de culturas foi estudado em um experimento conduzido desde 1994 na Estação Experimental da Epagri de Campos Novos, em um Nitossolo Vermelho. Os tratamentos de manejo do solo foram constituídos de uma combinação de cinco sistemas de preparo (PD = plantio direto; PE = preparo com escarificador + 1 gradagem; PC = lavração + 2 gradagens; PCq = PC com resíduos queimados e; PCr = PC com resíduos retirados) e cinco fontes de nutrientes (TT = testemunha, sem aplicação de nutrientes; AM = adubação mineral de acordo com a recomendação para cada cultura de verão; EA = 5 Mg ha-1 ano-1 de matéria úmida de cama de aviário; EB = 60 m3 ha-1 ano-1 de esterco líquido de bovinos e; ES = 40 m3 ha-1 ano-1 de esterco líquido de suínos). Foram avaliadas algumas propriedades físicas do solo associadas à forma da estrutura e a estabilidade de agregados após nove anos de condução do experimento e em cinco épocas durante o décimo ano; propriedades mecânicas e resistência à penetração foram determinadas em algumas combinações de tratamentos no décimo ano; temperatura e umidade do solo foram determinadas durante o ciclo da cultura do milho na safra 2003/2004, quando também foram avaliados o crescimento da parte aérea e sistema radicular do milho, bem como a produção de massa seca das culturas de cobertura de inverno e de grãos de milho. O PD apresentou maior densidade e menor macroporosidade e porosidade total logo após as operações de preparo e semeadura, mas estas diferenças reduziram com o passar do tempo. Todos os sistemas de preparo apresentaram maior estado de compactação na camada de 5 a 20 cm de profundidade após seis meses da última operação de preparo. Maior diâmetro médio de agregados secos ar foram observados nos tratamentos e profundidades com maior densidade do solo, indicando estreita associação entre estas duas variáveis. A estabilidade dos agregados, por sua vez, foi afetada por pequenas variações na umidade das amostras por ocasião da análise e maiores valores de estabilidade foram encontrados nos tratamentos de preparo com manutenção da palha na lavoura. Nas camadas superficiais do PD foi observada maior resistência mecânica à deformação, estimada pela tensão de pré-consolidação, e à penetração de raízes nas entrelinhas de semeadura sem tráfego recente. Na linha de semeadura e na entrelinha com tráfego recente as diferenças da resistência à penetração entre os sistemas de preparo foram menores. Maior temperatura do solo e maior amplitude diária foram observadas nos sistemas com maior revolvimento do solo, principalmente no início do ciclo da cultura do milho. Na camada superficial, após a ocorrência de chuvas, a umidade do solo reduziu mais rapidamente no PE, seguido do PC. No PD foi observado maior teor de umidade nesta camada mesmo em período prolongado de déficit hídrico, indicando ma ior armazenamento e disponibilidade de água para as plantas. Os tratamentos de aplicação de fontes de nutrientes tiveram pouco efeito sobre as propriedades físicas, hídricas e mecânicas do solo e sobre a temperatura e armazenamento de água, mas foram determinantes para o crescimento vegetativo e produção das culturas. Maiores crescimento e produção foram observados nos tratamentos com aplicação de cama de aviário e de esterco de suínos, resultado do efeito residual e imediato da aplicação destes materiais ao longo de nove anos. Entre os sistemas de preparo, a produção foi maior no PD, provavelmente em função do maior armazenamento e disponibilidade de água, já que a fertilidade do solo neste tratamento era inferior ao PE e PC ao final do nono ano.

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Collares, Gilberto Loguercio. "Compactação em latossolos e argissolo e relação com parâmetros de solos e de plantas." Universidade Federal de Santa Maria, 2005. http://repositorio.ufsm.br/handle/1/3308.

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Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul Soil compaction is closed related to agriculture as well as animal production management. Soil quality improvement has not been always achieved with use of soil conservation practice as no-tillage or use of animal production integrated to agriculture management. Agricultural traffic and soil management effects on soil compaction are not well known, specially associated to wet soils, and in many cases, has induced to compaction states which restrict crop growth and productivity, which in turn, has lead farmers to break the compaction using mechanical tools as plow or chisel. To better understand compaction effects and critical values of soil physical properties on black beans growth and productivity four studies were set up out in the field. Another field study were performed in five typical dairy farms in Rio Grande do Sul plateau which use systems with agriculture integrated with animal production, including forage management and time of grazing. The objective of this study was to study animal trampling effects on soil physical properties, bulk density, porosity and soil resistance. The first experiment cultivated black beansi in a clayey Oxisol with the following treatments: a) immediate compaction caused by traffic of 16.6 Mg front buck loader; b) chiseling and; c)residual compaction from six years no-tillage. The additional compaction affected mass-volume relations, soil moisture and resistance, a well as black beans growth and productivity. The other three experiments were carried out in an Alfisol from central depression of Rio Grande do Sul with objectives to compare effects of immediate and residual compaction and soil chiseled on soil physical properties and black beans growth and productivity. The immediate compaction was obtained by traffic of a 9 Mg buck loader on present soil condition and on soil compacted with 10 Mg one year ago. For studied Alfisol the bulk density which restricted crop growth and productivity had value higher than 1.7 Mg m-3. The state of compaction with bulk density higher than 1.8 Mg m-3 and macroporority lower than 0.1 m3 m-3 reduced black beans height, leaf area index and crop productivity in abou 50%. The negative effects of additional compaction were maintained after twelve months and succession of three crops (soybeans, oats and black beans), reducing the black benas productivity in 61.8 %. Breaking compaction of a Oxisol under six no-tillage or Alfisol under twelve years no-tillage by soil chiseling did not improve soil quality which induce significant black benas productivity. The bulk density expressed the increase of soil compaction caused by animal trampling, reaching values of 1.77 Mg m-3, measured immediately after animal trampling and, was more significant at superficial layers where the effects on macroporosity were greater. A compactação dos solos está intimamente relacionada com o manejo da agricultura e da pecuária na propriedade rural. A adoção de práticas conservacionistas como o plantio direto e a integração pecuária e agricultura não tem refletido em segurança aos agricultores quanto à melhoria permanente de aspectos físicos, químicos e biológicos do solo. O desconhecimento de ideais condições de trafegabilidade e manejo dos solos, associado à umidade inadequada às práticas agrícolas, tem aumentado a compactação do solo, podendo comprometer a produtividade e o desenvolvimento de plantas exigindo a adoção de medidas extremas como a escarificação do solo para melhorar a condição presente. Foram realizados quatro experimentos a campo, onde os efeitos da compactação causada pelo tráfego de máquinas foram avaliados pelos atributos do solo e no crescimento e produtividade da cultura do feijão. Outro estudo, realizado a campo, em cinco propriedades típicas de produção leiteira do planalto riograndense, que adotavam como sistema de produção a integração lavoura e pecuária, com distintos manejos de forrageiras e tempo de permanência dos animais nas glebas, teve por objetivo estudar o impacto do pisoteio animal nos atributos físicos do solo como: densidade, porosidade e resistência do solo a penetração. No primeiro experimento foi cultivado feijão em Latossolo argiloso do Planalto Gaúcho e se estabeleceu comparação entre: a) compactação imediata aplicada por tráfego de máquina com 16,6 Mg, b) compactação residual de 6 anos de plantio direto, e c) escarificação. A compactação adicional afetou as relações massa-volume, a umidade e a resistência do solo à penetração, assim como, a produtividade e o crescimento do feijoeiro. Os outros experimentos foram desenvolvidos em Argissolo da Depressão Central do RS, com o objetivo de comparar estados de compactação imediata, compactação residual aplicada em ano anterior e residual de compactação de 12 anos de plantio direto com a escarificação nas propriedades físicas do solo, na umidade e no crescimento e produtividade do feijoeiro. A compactação imediata foi obtida pelo tráfego de máquina com 9 Mg sobre o solo na condição presente e sobre resíduo de compactação de tráfego de 10 Mg aplicada em ano anterior. No Latossolo a densidade restritiva a produtividade do feijão e do trigo foi de 1,4 a 1,5 Mg m-3. Para o Argissolo, a densidade do solo restritiva a produtividade do feijoeiro foi superior a 1,7 Mg m-3. Os estados de compactação com densidade do solo maior que 1,8 Mg m-3 e macroporosidade menor que 0,1 m3 m-3, reduziram a altura de planta, a área foliar e a produtividade do feijoeiro em torno de 50 %. Os efeitos negativos da compactação adicional mantiveram-se após doze meses e sucessão de três cultivos (soja, aveia e feijão), reduzindo a produtividade de feijão em 61,8 %. O valor da densidade crítica baseada no intervalo hídrico ótimo (IHO) foi de 1,75 Mg m-3. A escarificação não representou ganho em qualidade do solo para áreas com seis anos de plantio direto em Latossolo e doze anos de plantio direto em Argissolo que implicasse em aumento de produtividade. A densidade do solo expressou o aumento da compactação do solo provocada pelo pisoteio animal, atingindo o valor de 1,77 Mg m-3 medida imediatamente após o pisoteio animal e mostrando-se mais significativa nas camadas superficiais do solo e, nessas, os efeitos na macroporosidade foram mais evidentes.

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43

Gavlasová, Iva. "Pedotransferové funkce pro odhad vlhkostních retenčních křivek středně těžkých půd jižní Moravy." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226857.

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The most important characteristics of each soil is its hydro-physical properties, which include retention curve. Retention curve expresses the relationship between humidity and pressure head. It is course affected by many factors such as grain size and mineralogical composition, humus content, structure and bulk density of dry soil. This thesis deals with direct and indirect determination of one of the basic hydraulic characteristics of the soil, soil moisture retention curve. For laboratory determination of moisture retention curves were used for sand tank and pressure instruments. Measured body retention curves were optimized RETC program.For indirect determination of retention curves were used Pedotransfer function by Wösten et . al .(1998 ) , derived from the European soils and under HYPRES Šútora and Štekauerová (2000). As in the project Wösten et al . (1998), PTF were processed for arable land in the area. The accuracy of both models PTF was assessed by the correlation coefficient R and standard error RMSE. Simple models PTF provide estimates of retention curves with sufficient accuracy for practical use in the locality.

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Olivera, Guerra Luis Enrique. "Suivi des ressources en eau des cultures irriguées par télédétection multi-spectrales optique/thermique." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30324.

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L'agriculture est une pression importante sur les ressources en eau, consommant plus de 70% de l'eau douce mobilisée à l'échelle mondiale. Cependant, les informations sur l'irrigation, pourtant cruciales pour assurer une durabilité de la ressource, sont souvent indisponibles. Par conséquent, il est essentiel d'estimer les différents termes du bilan d'eau des cultures à grande échelle. Cette thèse vise à intégrer les données de télédétection optique/thermique dans un modèle simplifié de bilan d'eau des cultures pour le suivi du bilan d'eau des zones agricoles irriguées. Une approche innovante est développée pour estimer simultanément l'irrigation, l'évapotranspiration (ET) et l'humidité en zone racinaire (RZSM) journalières à l'échelle de parcelle (ou à 100 m de résolution). Dans une première partie, une étude de faisabilité est réalisée à l'aide de mesures optiques/thermiques in situ collectées sur une parcelle de blé d'hiver dans la plaine du Haouz, au Maroc. En pratique, un coefficient de stress hydrique (Ks) dérivé de la température de surface (LST) et d'un indice de végétation (NDVI) est d'abord traduit en une première approximation de RZSM, qui est utilisée pour estimer les quantités et les dates d'irrigation au cours de la saison. Les irrigations obtenues permettent ensuite de forcer le modèle FAO-56 à coefficient cultural double (FAO-2Kc) et de fournir des ré-analyses ET et RZSM journalières. La RZSM ré-analysée est significativement améliorée par rapport aux premières estimations de RZSM, atteignant la même précision que celle obtenue en utilisant les irrigations réelles (RMSE=0,03 m3m-3 et R2=0,7). Toutefois, l'approche doit encore être testée avec des données satellitaires afin de démontrer son applicabilité dans le cas réel. La deuxième partie consiste à adapter l'approche précédente aux données optiques/thermiques Landsat à faible fréquence temporelle. Une méthode contextuelle est utilisée pour obtenir des estimations dérivées de Landsat (coefficients de culture et RZSM), qui sont utilisées pour réinitialiser un modèle basé sur le FAO-2Kc et propager ces informations à l'échelle journalière tout au long de la saison. Ensuite, les irrigations obtenues à l'échelle des pixels sont agrégées à la parcelle pour ré-analyser l'ET et la RZSM journalières. L'approche est appliquée sur trois zones agricoles (12 km x 12 km) de la région semi-aride de la plaine du Haouz et validée sur cinq parcelles de blé d'hiver avec différentes techniques d'irrigation (goutte à goutte, gravitaire et sans irrigation). Les résultats montrent que l'irrigation saisonnière sur l'ensemble des sites et des saisons est estimée avec une bonne précision (RMSE=44 mm et R=0,95), et ce quelque soit la technique d'irrigation. Des erreurs acceptables (RMSE=27 mm et R=0,52) sont obtenues pour des irrigations cumulées sur 15 jours, mais les erreurs sont beaucoup plus importants à l'échelle journalière et hebdomadaire. Cependant, les RZSM et ET journalières sont estimées avec précision à l'aide de des irrigations inversées et sont même très proches de celles estimées à l'aide des irrigations réelles (RMSE=0,04 m3m-3 pour RZSM et RSME=0,83 mm.d-1 pour ET). Dans la troisième partie, une méthode opérationnelle de désagrégation des données de LST basée sur les relations NDVI/LST et Landsat/MODIS est mise en œuvre pour améliorer la résolution spatio-temporelle de la LST utilisée en entrée de l'approche d'estimation de l'irrigation. La méthode de désagrégation est testée sur une région aride du Chili et sur notre zone d'étude dans la plaine du Haouz. La combinaison des données deLST Landsat et des données de LST désagrégées permet, grâce au gain en résolution temporelle, une meilleure détection des événements et des quantités d'irrigation. Le RMSE global de l'irrigation cumulée à différentes échelles de temps est réduite de 46 à 34 mm, tandis que le R passe de 0,50 à 0,64 Irrigated agriculture is an important pressure on water resources, consuming more than 70% of the mobilized freshwater resources at global scale. However, the information on irrigation, which is crucial for the sustainability of water resources in agricultural regions, is often unavailable. Therefore, monitoring and quantifying the crop water budget over extended areas is critical. This PhD thesis aims to integrate optical/thermal remote sensing data into a simplified crop water balance model for monitoring the water budget of irrigated agricultural areas. For this purpose, an innovative and stepwise approach is developed to estimate simultaneously the irrigation, the evapotranspiration (ET) and the root-zone soil moisture (RZSM) at crop field scale (100 m resolution) on a daily basis. In a first step, a feasibility study is carried out using in situ optical/thermal measurements collected over a winter wheat field of the Haouz plain, Morocco. A crop water stress coefficient (Ks) derived from the land surface temperature (LST) and vegetation index (NDVI) is first translated into RZSM diagnostic estimates, which is then used to estimate irrigation amounts and dates along the season. Next, the retrieved irrigations allow forcing the dual crop coefficient FAO-56 model (FAO- 2Kc) to re-analyze the daily ET and RZSM. The re-analyzed RZSM is significantly improved with respect to RZSM diagnostic estimates, reaching the same accuracy as that obtained by using actual irrigations (RMSE = 0.03 m3m-3 and R2 = 0.7). However, the approach needs to be tested using satellite data in order to demonstrate its real applicability. The next step consists in adapting the previous approach to spatially integrated but temporally sparse Landsat NDVI/LST data. For this purpose, a contextual method is first used to derive Landsat-derived estimates (crop coefficients and RZSM), which are used to re-initialize a FAO-based model and propagate this information daily throughout the season. Then, the retrieved pixel-scale irrigations are aggregated to the crop field-scale. The approach is applied to three agricultural areas (12 km by 12 km) in the semi-arid region of Haouz Plain, and validated over five winter wheat fields with different irrigation techniques (drip-, flood- and no-irrigation). The results show that the seasonal irrigation amounts over all the sites and seasons is accurately estimated (RMSE = 44 mm and R = 0.95), regardless of the irrigation techniques. Acceptable errors (RMSE = 27 mm and R = 0.52) are obtained for irrigations cumulated over 15 days, but poor agreements at daily to weekly scales are found in terms of irrigation. However, the daily RZSM and ET are accurately estimated using the retrieved irrigation and are very close to those estimated using actual irrigations (overall RMSE equal to 0.04 m3m-3 and 0.83 mm.d-1 for RZSM and ET, respectively). In a final step, an operational LST disaggregation method based on NDVI/LST and Landsat/MODIS relationships is implemented for enhancing the spatio-temporal resolution of LST as input to the irrigation retrieval approach. The disaggregation method is tested over an arid region of Chile and our study area in the Haouz Plain. Combining both disaggregated LST and Landsat LST data sets, thanks to the increase in the temporal frequency of LST data, results in a better detection of irrigation events and amounts. The overall RMSE of cumulated irrigation at different time scales is decreased from 46 to 34 mm, while the R is increased from 0.50 to 0.64. Consistently, the RZSM estimated using the disaggregated LST in addition to Landsat LST as input is improved by 26% and 14% in terms of RMSE and R, respectively

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Komárková, Markéta. "Vliv základní agrotechniky na fyzikální a hydrofyzikální vlastnosti půdy." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372322.

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In the master’s thesis, we evaluate the impact of different types of soil treatment on the physical and hydro-physical properties of the subsurface layers of soil. The experimental research took place near the town of Šakvice in two chosen areas treated conventionally, i.e. by tillage. The PRP SOL substance was applied to one of the observed areas. Unimpaired soil samples were taken during the vegetation period of the grown crops in the topsoil (10,20 cm) and in the undersoil (30 cm) on 13th May 2009 and on 10th September 2009. The chosen physical parameters of the soil, i.e. the reduced volume mass, the porosity, the distribution of pores, the actual content of water and air, were determined by standard analytical methods. The double-ring infiltration method was used during the field measuring of infiltration. The Philip’s equation and the Philip’s type three-parameter equation were used for the data analysis, serving as a base for estimation of saturated water content Ks. A protractor with a constant gradient was used during laboratory measuring. The results of a year-long research have not shown any major influence of the PRP SOL substance on the physical quality of the subsurface layers of soil in the observed area. On the contrary, the permeability od the soil obtained on the basis of Ks estimation is higher in the area treated by the PRP SOL substance.

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46

Schulte-Eickholt, Anna. "Erfassung, Analyse und Modellierung des Wurzelwachstums von Weizen (Triticum aestivum L.) unter Berücksichtigung der räumlichen Heterogenität der Pedosphäre." Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2010. http://dx.doi.org/10.18452/16187.

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Das Wurzelwachstum von Winterweizen wurde erfasst und modelliert, um teilflächenspezifisches Boden- und Düngemanagement zu verbessern. Die Variation von Wurzellängendichten im Feld wurde über zwei Vegetationsperioden hinweg an zwei unterschiedlichen Standorten in Ostdeutschland untersucht. Zur Auswertungserleichterung der hohen Anzahl an Wurzelproben, wurde eine halbautomatische Methode zur Bildanalyse von Wurzeln entwickelt. Der Einfluss von Änderungen bezüglich Bodenwasserstatus und Bodendichte bzw. Durchdringungswiderstand auf das Wurzelwachstum wurde untersucht. Die erhobenen Felddaten dienten gleichzeitig dazu, die Bodenwasser- und Wurzelwachstumsberechnung des Modells CERES-Wheat zu validieren. Das Modell simulierte die unterschiedlichen Bodeneigenschaften sowie die Wurzellängendichten und Bodenwassergehalte nur unzureichend. Der Effekt von Änderungen der Niederschlagsmengen auf die Simulationen von Wurzellängendichten und Bodenwassergehalten wurde anhand einer Unsicherheitsanalyse getestet und war extrem gering. Des Weiteren wurde eine Methode für praktische Zwecke entwickelt, mit der die Generierung von räumlich hoch aufgelösten Bodeninformationen unter Verwendung limitierter Eingangsdaten möglich ist. Die Modellkalkulationen basieren auf der Dempster-Shafer-Theorie. Anhand von multitemporal und multimodal erfassten Bodenleitfähigkeitsdaten, die Eingangsdaten für den Modellansatz sind, wurden Bodentypen und Texturklassen bestimmt. Das Modell generiert eine digitale Bodenkarte, die flächenhafte Informationen über Bodentypen und Bodeneigenschaften enthält. Die Validation der Bodenkarte mit zusätzlich erhobenen Bodeninformationen ergab gute bis sehr gute Ergebnisse. Winter wheat root growth was measured and modelled to improve site-specific soil and fertilizer management in commercial wheat fields. Field variations in root length densities were analysed at two contrasting sites in East-Germany during two vegetation seasons. A semi-automated root analysing method was developed to facilitate analyses of large numbers of samples. Influences of variations in soil water states, bulk densities and penetration resistances on spatial distributions of roots were quantified. Differences in soil characteristics were large between the two sites and affected root growth considerably. The same field data was used for validating the soil moisture and root growth calculations of the widely applied growth model CERES-Wheat. Simulations of root length densities, soil physical properties and soil water contents were inadequate. The effects of changes of rainfall variabilities on simulated root length densities and soil water contents were tested by uncertainty analysis but were negligible low. A methodology for generating soil information for practical management purposes at a high degree of spatial resolution using limited input information was developed. The corresponding model calculations were carried out based on the Dempster and Shafer theorem. Soil types and texture classes were determined with multimodally and multitemporally captured data of soil electrical conductivities which are required input data of the new model approach. The model generates a digital map with extensive information of spatial variations in soil properties. The validation of the generated soil map with soil data from independent measurements yielded close correlation between measured and calculated values.

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Gherardi, Mark James. "Availability and management of manganese and water in bauxite residue revegetation." University of Western Australia. Soil Science and Plant Nutrition Discipline Group, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0038.

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[Truncated abstract] Industrial processing to refine alumina from bauxite ore produces millions of tonnes of refining residue each year in Australia. Revegetation of bauxite residue sand (BRS) is problematic for a number of reasons. Harsh chemical conditions caused by residual NaOH from ore digestion mean plants must overcome extremely high pH (initially >12), saline and sodic conditions. At such high pH, manganese (Mn) is rapidly oxidised from Mn2+ to Mn4+. Plants can take up only Mn2+. Thus, Mn deficiency is common in plants used for direct BRS revegetation, and broadcast Mn fertilisers have low residual value. Added to this, physical conditions of low water-holding capacity and a highly compactable structure make BRS unfavourable for productive plant growth without constant and large inputs of water as well as Mn. However, environmental regulations stipulate that the residue disposal area at Pinjarra, Western Australia, be revegetated to conform with surrounding land uses. The major land use of the area is pasture for grazing stock. Hence, pasture revegetation with minimum requirement for fertiliser and water application is desirable. This thesis investigates a number of avenues with potential for maintaining a productive pasture system on BRS whilst reducing the current level of Mn fertiliser and irrigation input. Emphasis was placed on elucidation of chemical and physical factors affecting Mn availability to plants in BRS

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Belehu, Terefe. "Agronomical and physiological factors affecting growth, development and yield of sweet potato in Ethiopia." Thesis, 2003. http://upetd.up.ac.za/thesis/available/etd-07262004-141704.

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HO, SHIH-SHEN, and 何信賢. "Model on soil moisture movement of unsaturated condition in root zone." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/07701145525696416672.

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"Field-scale root-zone soil moisture : spatio-temporal variability and mean estimation." Thesis, 2015. http://hdl.handle.net/10388/ETD-2015-12-2397.

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This thesis is focused around improving soil moisture estimates of spatial variability and mean at the field scale, which are useful for many different applications. The objectives were: (1) examine soil moisture spatial patterns and variability within field scale, and (2) compare field-scale soil moisture determination methods. An observational study was conducted, in which soil moisture was monitored over a 500 m by 500 m area during two and a half growing seasons at a prairie pasture in central Saskatchewan. Analysis of the spatial patterns of root-zone soil moisture revealed two distinct spatial patterns representing wet (spring) and dry (fall) periods. The relationship between spatial variability and mean soil moisture was found to follow an unusual concave trend, where variability was smallest at mid-range moisture contents. These spatial variability characteristics are a result of differences in participation level. Some locations were non-participating having only small moisture changes over the growing season, while others were dynamic having large changes. At the pasture site, these participation differences are a result of high soil heterogeneity, which may be characteristic of Solonetzic soils. In the second part of this thesis, methods to determine mean field-scale root-zone soil moisture were evaluated. The cosmic-ray neutron probe has the most potential for providing field-scale measurements. However, these measurements are only representative of moisture in the top 20 cm of soil, and need to be scaled up in order to represent the entire root-zone (0–110 cm). The three scaling methods applied to obtain lower root-zone soil moisture were: (1) a single time stable location, (2) representative landscape unit, where a single monitoring profile for each vegetation type was used, and (3) modeling by exponential filter. The representative landscape unit approach estimated soil moisture changes well, but not volumetric water content. The time stability method performed the best, followed by the exponential filter. However, the exponential filter has more potential, as the time stability method is difficult to apply to other field sites; particularly those without existing soil moisture instrumentation, due to its calibration requirements. The findings of this thesis make a contribution to the large body of existing literature on soil moisture variability and scaling. Suggestions for future research are provided.

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Dissertations / Theses on the topic 'Root density; soil moisture'

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