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1
El-Bishti, Magda Bashier. "Determination of soil moisture using dielectric soil moisture sensors : effect of soil temperature and implication for evaporation estimates." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487102.
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The reliability and accuracy of several sensors that employ the relationship between dielectric constant and soil moisture constant, e, in particular capacitance sensors were investigated. Results obtained from laboratory examinations ,of a Theta probe, TP, selected as a representative model for capacitance sensors, suggested that the sensor output was affected by temperature variations, electrical conductivity levels, spatial variation in sample bulk density as well as the level of compaction of the soil surrounding the sensor's rods. Detailed in situ e data collected usmg capacitance sensors were used to calculate sub-daily estimates of evaporation, E, using the soil water balance method, combined with the zero-flux-plane (ZFP) approach, for plots of bare soil, rapeseed and a maize field. These sensors comprised Theta probes (TP), Profiles probes (PP), ECH20 probes (EP) and Aquaflex sensors (AF). / The field output data of these sensors were analysed and compared with e obtained with both, the gravimetric and neutron probe method. The absolute values of B as measured by the various capacitance sensors differed considerably. Furthermore, the outputs of these sensors (apart from the AF probes) were found to be affected by temperature, which would result in an anomalous course of diurnal E. Also, B-data were subject to noise which required smoothing to ensure a physically realistic variation in E, when compared to estimates with the Penman-Monteith equation, EPAf, and the eddy-covariance method (maize field). E was determined from diurnal changes in vertically integrated soil moisture content above the ZFP. Smoothed values of Bwere temperature-corrected using fieldbased and laboratory-based correction equations. A considerable difference between field- and laboratory-based temperature corrections procedures was noticed, and correction factors strongly depended on B. As this resulted in an overly complicated correction procedure, which consequently gave unreliable E-values, it was then decided to use a constant correction factor (based on the field correction procedure), for each capacitance probe. For the bare soil plot, with the exception ofPP and EP only Bprofiles obtained with the TP and AF sensors produced relatively reliable E values when compared to Enf. By contrast, when these capacitance sensors were used under a canopy, all sensors yielded satisfactory E-values. This was most likely caused by reduced amplitudes of soil temperatures under the canopy and the fact that the dimensions of most sensors do not allow installation in the top soil (~3-5cm) layer at which most evaporation would take place in bare soils. We therefore recommended that these sensors can be used for diurnal B measurements and E determination under canopy provided that an appropriate temperature-correction procedure for each sensor is applied. To obtain reliable Band E estimates in bare soil, more research needs to be done. For more reliable e and E estimations in bare soils further extensive field trials would be strongly advised
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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.<br>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.<br>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.<br>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.<br>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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Zeywar, Nadim Shukry 1959. "Effect of sensor placement on the relationships of crop water stress index, soil moisture tension and soil moisture content." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/191981.
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A field experiment was conducted to investigate the feasibility of making one measurement of soil moisture tension/content or crop water stress index (CWSI), and from it determine when and how much to irrigate. Cotton (Gossvpium hirsutum C.V. DPL-90) was planted in a sandy loam soil prepared with an underground drip irrigation system. Measurements of soil moisture tension, soil moisture content, plant temperature, and wet- and dry-bulb temperatures were made. The results indicate that soil moisture tension above 0.30 m and soil moisture content above 0.50 m in the root zone can be used as good indicators for CWSI or vice versa. Further work is required using different irrigation systems and different crops in larger land areas.
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Kim, Bruce Chang Shik. "MULTI-STEP ELECTROCHEMICAL IMPULSE GENERATOR AND POTENTIAL MONITORING SYSTEM." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275454.
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Park, Jin Young. "A critical assessment of moist tamping and its effect on the initial and evolving structure of dilatant triaxial specimens." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/23949.
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Kelley, Elizabeth Jane. "The effects of soil moisture on pavement systems." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175799994.
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Barrak, Khalid Mohamed 1956. "Effects of various mulches on soil moisture conservation." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/191944.
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The purpose of this work was to study and evaluate the effect of various mulches on the soil moisture content for sandy loam soil under high temperatures. The straw, wood shavings, and rock fragments were used with different rates of application for covering soil. Treatments were compared to bare soil. The moisture content was significantly higher for mulched treatments. However, the effectiveness of wood shavings and rock fragments mulches did not seem different in soil moisture content, while straw mulch did. The soil moisture content for the straw had the highest value at the end of the experiment. The straw mulch apparently conserved soil moisture over the other treatments. The conservation of soil moisture under 10, 15, 20 gm of straw mulch was occasioned by less direct contact soil surface with air surface and less possibility of heat transfer. The greatest savings in water was under 2.7 tons/ha of straw mulch.
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Fuhrmann, Andrew. "Effect Of Rainfall Events On The Thermal And Moisture Exposure Of Underground Electric Cables." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/331.
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Cable ampacity analysis is generally performed assuming constant worst-state environmental conditions, which often correspond to a dry soil condition or to a condition with uniform ambient soil moisture content. The characteristic time scale of thermal variation in the soil is large, on the order of several weeks, and is similar to the time scale between rainfall events in many geographic locations. Intermittent rainfall events introduce significant transient fluctuations that influence the thermal conditions and moisture content around a buried cable both by increasing thermal conductivity of the soil and by increasing the moisture exposure of the cable insulation. This paper reports on a computational study of the effect of rainfall events on the thermal and moisture transients surrounding a buried cable. The computations were performed with a finite-difference method using an overset grid approach, with an inner polar grid surrounding the cable and an outer Cartesian grid. The thermal and moisture transients observed in computations with periodic rainfall events were compared to control computations with a steady uniform rainfall. Under periodic rainfall conditions, the temperature and moisture fields are observed to approach a limit-cycle condition in which the cable surface temperature and moisture content oscillate in time, but with mean values that are significantly different than the steady-state values.
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Schuster, Doug E. "Soil Moisture Effects on Supercellular Convective Initiation and Atmospheric Moisture in the Midwestern United States." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1462232761.
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Papadopoulos, Anastasios K. "Nitrogen and moisture distributions under subirrigated soybeans." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55520.
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A field lysimeter experiment was conducted on a sandy loam soil during the 1990 and 1991 growing seasons. The experiment tested the effects of different watertables on soybean yields, and on moisture distribution and nitrogen concentration of the soil profile. The watertable depths were 40, 60, 80, and 100 centimeters (cm).<br>Yields were measured in terms of number of beans per plant, number of pods per plant, number of beans per pod, and seed protein content at harvest.<br>Soil samples collected at depths of 30 and 70 cm from the soil surface were analyzed for moisture content and NO$ sb3 sp-$-N and NH$ sb4 sp+$-N concentrations.<br>The experimental results showed that controlled watertable management increased the yield and decreased soil NO$ sb3 sp-$-N levels. The best results from the watertables tested were found to be at 60 and 80 cm. This is suggested as the range of watertable depths that should be maintained for optimum soybean production.
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Matheron, Michael, Martin Porchas, and Michael Maurer. "Effect of Temperature and Moisture on Survival of Phytophthora in Citrus Grove Soil." College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/223839.
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Before replanting a citrus grove in Arizona, different preplant cultural activities may be performed, such as immediate replanting of the new citrus grove, allowing soil to lay fallow for various lengths of time, or planting the site to alfalfa for one or more years before the new citrus grove is established. A study was conducted to compare the effect of these different cultural preplant practices on the survival of Phytophthora in citrus grove soils. In June, 1998, and July, 1999, a total of 18 soil samples were collected within mature lemon groves. Each initial bulk sample was pretested, found to contain Phytophthora parasitica, then thoroughly mixed and partitioned into 1-liter plastic containers, which were subjected to different environmental and cultural conditions. The soil in each 1-liter container was tested for the presence of P. parasitica 1 and 3.5 to 4 months later. All soil samples then were placed in the greenhouse and a 6-month-old Citrus volkameriana seedling was planted in soil samples not containing plants. Three 1-liter sub-samples from each of ten 7-liter volumes of soil incubated outside for three months were also planted to citrus in the greenhouse. The soil containing plants in the greenhouse was watered as needed for 3 months, then again tested for the presence of Phytophthora. Irrigating soil infested with Phytophthora parasitica, whether it was planted to a host (citrus) of the pathogen, planted to a non-host (alfalfa) of the pathogen, or not planted at all, did not lower the pathogen to nondetectable levels. Phytophthora became and remained nondetectable only in the soil samples that were not irrigated and subjected to mean temperatures of 35 to 37° C (94 to 98° F). On the other hand, the pathogen was detectable in some soil samples subjected to dryness at lower mean temperatures of 26 to 30° C (79 to 86° F) after a citrus seedling subsequently was grown in the soil for 3 months. A dry summer fallow period following removal of a citrus grove (including as much root material as possible) was the only cultural practice among those tested that reduced the level of Phytophthora to nondetectable levels in all soil samples tested.
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El-Majbari, Farag Ali Mustafa 1946. "Effect of soil moisture stress on photosynthesis and other physiological characteristics of seven sorghum cytoplasms." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277168.
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The experiment was conducted at the University of Arizona Campus Agricultural Center to evaluate the effect of soil moisture stress on photosynthesis, transpiration, diffusive resistance, temperature differential, leaf temperature, and specific leaf weight of seven sorghum Sorghum bicolor (L.) Moench cytoplasms represented by nine lines. As soil moisture stress increased, diffusive resistance and leaf temperature increased whereas photosynthesis and transpiration decreased. Temperature differential was highest under high soil moisture stress and lowest under medium soil moisture stress. Specific leaf weight was highest under medium soil moisture stress. Three lines, AKS37, AKS38, and A2Tx398, representing two different germplasms under high soil moisture stress exhibited high photosynthesis and transpiration rates, high specific leaf weights, and low diffusive resistance. Differences in photosynthesis rates under non-soil moisture stress between A1 and A2 cytoplasmic sterility systems were significant.
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Abel, David Scott. "Cover crop effects on soil moisture and water quality." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/34650.
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Master of Science<br>Department of Agronomy<br>Nathan O. Nelson<br>Eutrophication of freshwater lakes and streams is linked to phosphorus (P) fertilizer loss from agriculture. Cover crops could help mitigate P loss but producers are concerned that they may use too much water. This study was conducted to better understand the effects cover crops have on soil moisture and P loss. Volumetric water content (θ) was measured at the Kansas Cover Crop Water Use research area at 10 depths throughout a 2.74 m soil profile in 5 cover crop treatments and compared to θ measured from a chemical fallow control. Total profile soil moisture in sorghum sudangrass (1.02 m) and forage soybean (1.03 m) did not significantly differ from chemical fallow (1.05 m) at the time of spring planting. However, water deficits were observed in double-crop soybean (1.01 m), crimson clover (0.99 m), and tillage radish (0.99 m). At the Kansas Agricultural Watersheds, runoff was collected and analyzed for total suspended solids, total P, and DRP from 6 cover crop/fertilizer management treatments over two years. In the first water year the cover crop reduced runoff, sediment, and total P loss by 16, 56, and 52% respectively. There was a significant cover by fertilizer interaction for DRP loss. When P fertilizer was broadcasted in the fall with a cover crop, DRP loss was reduced by 60% but was unaffected in the other two P fertilizer treatments. Results were different in the second water year. The cover crop reduced sediment loss (71% reduction), as was seen in year one, but neither the cover crop nor the fertilizer management had a significant effect on runoff volume or total P loss overall. Contrary to the 2014-2015 results, cover crop increased DRP load by 48% in 2015-2016. DRP load was 2 times greater in the fall broadcast treatment than it was in the spring injected treatment but there was not a significant fertilizer by cover crop interaction. In order to determine the long term effects of cover crops and P fertilizer management P loss parameters should be tracked for several more years.
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Lee, Khil-Ha. "Effect of vegetation characteristics on near soil moisture retrieval using microwave remote sensing technique." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280028.
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Passive microwave remote sensing has shown potential for monitoring near surface soil moisture. This dissertation presents a new approach to representing the effect of vegetation on microwave emission by extending an existing model (Wilheit, 1978) of the coherent propagation of electromagnetic radiation through a stratified medium. The resulting multi-layer microwave emission model is plausibly realistic in that it captures the behavior of the vegetation canopy by considering the dielectric permittivity of the mixture of air and vegetation matter in the canopy and recognizing the vertical distribution of dielectric permittivity through the canopy. The model parameters required to specify the dielectric profile within the canopy are not usually available from data taken in typical field experiments, particularly the parameters that quantify the way the dielectric permittivity of the vegetation and air mix together to give the dielectric permittivity of the canopy. Thus, the feasibility of specifying these parameters using an advanced single-criterion, multiple-parameter optimization technique was investigated. The resulting model was also applied to investigate the sensitivity of microwave emission to specific vegetation parameters. The study continued with an investigation of how the presence and nature of vegetation cover influences the values of geophysical variables retrieved from multi-angle microwave radiometer spectrometer observations, using the upcoming Soil Moisture Ocean Salinity (SMOS) mission as a case study. The extended version of the Wilheit (1978) model was used to calculate synthetic observations of microwave brightness temperature at the look-angles proposed for the SMOS mission for three different soil moisture states (wet, medium, and dry) and four different vegetation covers (grass, crop, shrub, and forest). It was shown that retrieved values are only accurate when the effective values of the opacity coefficient used in the Fresnel model are made to vary in a prescribed way with look-angle, soil moisture status, and vegetation. The errors in retrieved values that may be induced by poor specification of vegetation cover were investigated by imposing random errors in the values of vegetation-related parameters in the forward calculations of synthetic observations made with the extended Wilheit model. The results show that poorly specified vegetation can result in both random and systematic errors in the retrieved values of the geophysical variables. (Abstract shortened by UMI.)
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Post, Donald F., Jamie P. Dubay, and Allan D. Matthias. "The Effects of Rock and Green Waste Mulches on Soil Moisture and Soil Temperature." Arizona-Nevada Academy of Science, 2000. http://hdl.handle.net/10150/296563.
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Saldanha, Sachin Mervin. "Effect of moisture content on the desorption of carbon tetrachloride from Hanford silt." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/s_saldanha_050409.pdf.
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Thesis (M.S. in environmental engineering)--Washington State University, May 2009.<br>Title from PDF title page (viewed on June 19, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 58-61).
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Doulis, Andreas G. "The influence of low moisture stress on the gas exchange and thylakoid activity of loblolly pine (pinus taeda) and aleppo pine (pinus halepensis)." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41990.
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Liaghat, Abdolmajid. "Effect of clay type and clay content on moisture content and bulk soil electrical conductivity as measured using time domain reflectometry." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68199.
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Time domain reflectometry (TDR) is becoming a widely used method to determine volumetric soil water content ($ theta$) and bulk soil electrical conductivity (EC$ sb{ rm a}$). It has been found that the $ theta$ and EC$ sb{ rm a}$ values obtained by this method, on certain soils, require calibration. The purpose of this study was to monitor the effects of soil texture (most particularly the clay type and clay content) on $ theta$ and EC$ sb{ rm a}$ estimated by TDR.<br>Water content was measured, gravimetrically and by TDR, on packed columns of nine soil mixtures, composed of three clay types (Hydrite, Bentonite, and Ste. Rosalie clay) and coarse sand at three levels (8, 16, and 30% by weight) of these clay materials. Three replicates of each mixture (a total of 27 columns) were made to statistically establish the effect of the clay type and the clay content on $ theta$ and EC$ sb{ rm a}$ readings by TDR. It was found that the TDR overestimated $ theta$ for the Hydrite and Ste. Rosalie (Natural) materials but accurately predicted for the Bentonite materials, compared to gravimetric determinations.<br>Bulk soil electrical conductivity was simultaneously measured by two independent techniques, TDR and 4-probe, on the same soils. It was found that the clay types and clay contents have almost equal effects on the EC$ sb{ rm a}$ as measured by TDR and 4-probe techniques. It was found that the estimated EC$ sb{ rm a}$ values obtained by TDR and 4-probe methods for the fine-textured Bentonite materials were lower than those for the Hydrite and Ste. Rosalie materials at equal $ theta$ and EC$ sb{ rm W}$ (electrical conductivity of soil water).
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Al-Shehry, Jaber Mohammed. "EFFECT OF GUAR GUM ON VEGETABLE TRANSPLANT GROWTH." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275440.
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Momayyezi, Mina. "The effect of soil moisture stress on allelopathic influence of hound's-tongue (Cynoglossum officinale L.)." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/40927.
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Little information on the effect of environmental stressors on hound’s-tongue interaction with associated herbivores and grasses is available. This study investigated the effect of soil moisture stress (SMS) on allelopathic influence of hound’s-tongue on a) feeding preference and growth of grasshopper (Melanoplus sanguinipes Fab.) and b) seed germination and seedling growth of Idaho fescue (Festuca idahoensis Elmer), bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. and J. G. Sm.), and hound’s-tongue (Cynoglossum officinale L.). Hound’s-tongue plants were grown under four SMS levels [100, 80, 60, and 40% field capacity (FC)] in a greenhouse.
On intact hound’s-tongue, grasshoppers preferred mid-aged leaves of plants at 40% FC; whereas there was no consistent relationship between the leaf age and the area consumed for plants at 100% FC. Grasshoppers showed no statistically significant preference for discs excised from old leaves at 100 vs. 80, 60, or 40% FC. However, analyses of pooled results showed their preference for discs from old leaves at 60 and 40% over 100% FC. In bioassays employing discs from young leaves, grasshoppers significantly preferred young leaves at 40 compared to 100% FC. In disc choices between young and old leaves of plants at the same SMS, grasshoppers preferred young over old leaves at 40% FC. The greater preference and higher growth of grasshoppers on younger leaves of plants grown under higher SMS could increase our understanding of the effect of insects’ herbivory on hound’s-tongue under various SMS in rangelands.
Inhibitory effects of hound’s-tongue leaf leachate on germination of hound’s-tongue and bluebunch wheatgrass and seedling growth of grasses increased with SMS only in one Petri dish experiment. In soil, hound’s-tongue leaf leachate and leaf residue from plants grown under SMS had either no or inconsistent allelopathic effects on seedling growth of grasses. Hound’s-tongue root elongation was inhibited in soil covered with residue from 40 compared to 80% FC plants. This study suggests that SMS could increase the inhibitory effect of hound’s-tongue mother plants on growth of its seedlings, but it may not have any ecologically significant effect on the allelopathic influence of hound’s-tongue on germination and seedling growth of neighboring grasses in nature.
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Mushia, Mahlodi Nicacius. "Evaluating the effect of moisture stress on tomato using non-destructive remote sensing techniques." Thesis, University of Limpopo, 2009. http://hdl.handle.net/10386/498.
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Thesis (MSC.Agriculture)) --University of Limpopo, 2009.<br>The aim of this experiment was to evaluate the effect of moisture stress on tomato, using non-destructive remote sensing techniques and agronomic traits under field and greenhouse conditions. Two tomato cultivars Roma VF and Flora Dade were used for the trial. The soil was fertilized optimally for all nutrients to avoid other stresses except water stress; a 2x2 factorial experiment was conducted using two levels of water regimes (stressed vs. control (non-stressed)) having four replicates and two cultivars using a Completely Randomized Design. Pots were put under greenhouse and field conditions. Canopy temperature was measured using an infrared thermometer, NDVI values were recorded using a green seeker hand-held optical sensor unit and stomatal opening were determined using a leaf porometer. Other agronomic traits including days taken for 50% flowering, plant height, number of fruits per plant and fruit yield per plant were recorded. Leaf temperature in stressed plants was high as compared to non-stressed plants, whereas NDVI and stomata conductance values were low. Number of fruits per plant was low; each plant had 4.00 fruits under field conditions and 5.00 fruits per plant under greenhouse conditions as compared to 9.00 fruits under field conditions and 13.00 under greenhouse conditions for non stressed plants. Stressed plants were shorter as compared to non-stressed plants and days taken for 50% flowering were delayed in both cultivars for stressed plants. Stressed plants showed a sign of stress at early stages of plant development. Most of these signs were found on the plants rather than on the fruits, the shape of the main stem of a growing plant was one of the good indicators as it became thin and stringy under stressed conditions. The experiment showed that it is possible to evaluate the effect of moisture stress on tomato by the use of canopy temperature, NDVI, stomatal conductance and agronomic traits.
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Paech, Robert J. "The effect of soil moisture stress, rewatering and leaf washing on the efficacy of glyphosate on selected plant species /." St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17705.pdf.
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Dolling, P. J. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.
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Semon, Mande 1957. "Interplot and intraplot border effects on maize genotypes under two levels of moisture availability." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276817.
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The performance of three maize (Zea mays L.) hybrids, grown under two irrigation levels, was used to investigate the effects of soil moisture competition between adjacent plots, the transmission of these effects into multi-row adjacent plots and types of multi-row plots and plot borders most effective in shielding from these interplot competition effects. On the basis of grain yield, competition effects intended to the second rows of five-row plots necessitating more than five-row plots to accurately evaluate the full transmission of interplot competition effects into adjacent plots. Evaluation of genotypes in one-row plots all with the same common border row genotype to make them three-row plots would be more suitable for evaluation of relative competitiveness for soil moisture under soil moisture stress conditions compared to no border rows or border rows of the same genotype being evaluated.
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Liang, Jiansheng. "Xylem-carried abscisic acid (ABA) in plant responses to soil-drying." HKBU Institutional Repository, 1997. http://repository.hkbu.edu.hk/etd_ra/167.
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Al-Ismaily, Said Salim. "Nitrogen mineralization of manure-amended soil: Effects of salinity and moisture content." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290018.
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Application of manure has been used to increase the nitrogen status of many arid and semi-arid agricultural soils, however, organic nitrogen contained in animal manures must be mineralized prior to utilization by crops. Nitrogen mineralization is, like other biological processes, affected by soil water status. This can be due to the direct influence of soil moisture and/or salt interactions on the nitrogen dynamics. It is critical to understand the interactive effects of salt and water on nitrogen in soils amended with organic fertilizer. Such knowledge may be used for improving and quantifying nitrogen use efficiency. Objectives of this study were (i) to examine the relative and interactive influences of soil osmotic and matric water potentials on nitrogen transformations in manure-amended and non-manured soils, (ii) to determine the extent of nitrogen mineralization over a range of soil water potentials, and (iii) to study the effect of manure addition on nitrogen dynamics in an agricultural desert soil. Gila fine sandy loam soil was treated by addition of varying amounts of distilled water, NaCl, and dairy manure and incubated at depth of 20 cm in 0.025 mm thickness Ziploc® bags. Ammonium nitrogen, nitrate nitrogen, gravimetric soil moisture content, and total soil water potential were measured weekly for 16 weeks. Our study showed a decrease in the amount of inorganic N released from both the non-manured and manure-amended soils at total soil water potentials of approximately -55 bars or less. Maximal amounts of inorganic-N were released at potentials of -23 to -3.5 bars. There was an accumulation in the amounts of NH₄-N released at potentials of -55 bars or less, presumably because of a reduction in net nitrification. The manure caused nitrogen immobilization especially during the early part of our study. Immobilization also occurred in non-manured soil, but this generally lasted only a few weeks. Immobilization was prolonged in soils with lower water potentials. Net N mineralization in the manure-amended soils was higher than in the non-manured soils when soil moisture content was at field capacity.
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Nciizah, Adornis Dakarai. "Cattle manure, scalping and soil wetness effects on some physical properties of a hardsetting soil and associated early maize growth." Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/349.
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Most soils in the Eastern Cape Province, South Africa are shallow and are low in organic matter. Therefore these soils are structurally fragile and highly susceptible to inherent degradative processes like hardsetting. The objective of this study was to determine the effect of cattle manure, scalping and soil wetness on aggregate stability, penetration resistance and early maize growth in hardsetting soils. Glasshouse and field studies were conducted to determine the effect of cattle manure on aggregate stability and penetration resistance of freshly exposed topsoils by scalping at 0, 10 and 20 cm depths. In the glasshouse cattle manure was applied at 0 and 20 Mg/ha and matric suction was kept at ~ 30 and ~ 400 kPa; contrasting high and low soil wetness. Three soils were put in pots and arranged in a randomized complete block 3 2 2 factorial design. The field study was done at the University of Fort Hare research farm and the treatments were arranged in a split-plot complete randomized design with three replications. Scalping treatment was the main plot whilst the quantity of the cattle manure applied was the sub plot. Cattle manure increased mean weight diameter (MWD) by between 48% and 71% under glasshouse and between 18% and 33% under field conditions, depending on the soil wetting rate. Cattle manure reduced MWD when the soil under field condition was subjected to mechanical shaking. Soil penetration resistance decreased linearly, with increasing soil wetness but it rapidly increased with increase in matric suction up to ~200 kPa and thereafter the rate of increase reduced. In the glasshouse, all treatments had no significant effects on shoot dry weight but low matric suction increased root dry weight by 133%. Interaction of cattle manure and low matric suction reduced shoot length by 6%, shoot fresh weight by 25%, root surface area by 36%, root length by 5% and root fresh weight by 29% compared to the control. In contrast, application of cattle manure and high matric suction increased shoot length by 37%, shoot fresh weight by 136%, root surface area by 159%, root length by 94% and root fresh weight by 119%. In the field, cattle manure application increased root length density and shoot dry matter by 26% and 30% respectively. Cattle manure improved the stability of aggregates of the hardsetting soil under rapid or slow water intake conditions experienced during rainfall or irrigation. However, under field conditions cattle manure acted as a deflocculant and decreased the stability of aggregates when mechanical stress was applied. The effectiveness of cattle manure in improving maize growth in hardsetting soils was determined by matric suction.
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Rahman, Azizur 1954. "Effects of soil moisture stress and inter-plot competition on grain yield and other agronomic characteristics of sorghum and pearl millet." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277218.
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Sorghum (Sorghum bicolor L., Moench) and pearl millet (Pennisetum americanum L., Leeke) were intercropped under soil moisture non-stress and stress at Marana, Arizona during summer 1987. Effects of soil moisture stress and inter-row competition between sorghum and pearl millet on grain yield, 50% bloom, plant height, head length, head exsertion, 1000 grain weight, and number of effective tillers were evaluated. Interplot competition significantly reduced grain yield and head exsertion of peal millet. In sorghum, only plant height was significantly different due to competition. Agronomic characters were significantly different due to the effect of soil moisture stress except head length in pearl millet and head length, 1000 seed weight, and number of effective tillers in sorghum. Sorghum growing in a neighbor plot greatly suppressed millet grain yield under soil moisture stress. Relative yield total of the cereals under intercrop was less than unity under soil moisture stress.
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Bond, Alison. "Germination ecology of Carex (Cyperaceae), effects of light, stratification, and soil moisture." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ50722.pdf.
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Bond, Alison Marguerite. "Germination ecology of Carex (Cyperaceae) : effects of light, stratification, and soil moisture." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21514.
Full textAbstract:
Congeneric species occupying different habitats might be expected to have different seed dormancy strategies and germination requirements while those growing in the same habitats may be more similar. I tested this hypothesis with a broad survey of the germination of 51 Carex species from mesic deciduous forests, wet deciduous forests, and wetland or seasonally flooded areas in response to different controlled environmental conditions. A canonical discriminant analysis based on the responses of 29 species to various treatments showed clear differences among seeds from each habitat with respect to germination behaviour. Germination of seeds from mesic deciduous forest species was generally faster after moist stratification than after either submersion or dry storage. In seeds from most wet areas of deciduous forest, wetland, or seasonally flooded habitats, germination was similar or greater after submerged as compared to moist stratification. Total germination was significantly increased by light in all species except Carex pedunculata , an ant-dispersed species. Germination was not significantly different on a poorly drained peat soil than on a well-drained sandy loam. Seeds of most species were at least physiologically dormant at maturity and germination of fresh seeds was generally low. Spring germination was similar among species from all habitats and generally began in late May or early June, at fairly high temperatures (min 7°C, max 17°C), which is unusual for forest species but consistent among Carex species.
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Teclehaimanot, Dawit Lee Jejung. "Quantitative analysis of moisture content and temperature of landfill soil cover and their effect on methane emission." Diss., UMK access, 2005.
Find full textAbstract:
Thesis (M.S.)--Dept. of Geosciences. University of Missouri--Kansas City, 2005.<br>"A thesis in urban environmental geology." Typescript. Advisor: Jejung Lee. Vita. Title from "catalog record" of the print edition Description based on contents viewed March 12, 2007. Includes bibliographical references (leaves 116-119). Online version of the print edition.
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Wraith, Jon M. "Effect of Short Duration Grazing on Soil Moisture Depletion and Plant Water Status in a Crested Wheatgrass Pasture." DigitalCommons@USU, 1986. https://digitalcommons.usu.edu/etd/6445.
Full textAbstract:
A short duration grazing system was utilized to determine the effects of intensive periodic defoliation during spring on soil moisture depletion patterns and plant water status in a crested wheatgrass (Agropvron cristatum and A. desertorum) pasture in central Utah. Exclosures were constructed to compare grazed and ungrazed responses. Soil moisture was monitored to a depth of 193 cm at one to two week intervals from mid-April to late-September using a neutron moisture gauge. Predawn and midday leaf water potentials were estimated using a pressure chamber technique. The two paddocks included in the study were grazed three times between mid-April and mid-June in 1985. A difference in time of grazing between the two paddocks was also examined for its effect on soil moisture depletion patterns and plant water status. Soil moisture was depleted at a higher rate within ungrazed plots than grazed plots during 13 April to 1 July in both paddocks. Soil moisture was depleted at a higher rate after 1 July in grazed compared to ungrazed plots in the early-grazed paddock; however, no difference in soil moisture depletion rate was noted after 1 July within the late-grazed paddock. Total cumulative depletion was greater within ungrazed plots than grazed plots in the early-grazed paddock from 6 June until 13 August, and from 23 May until 30 July in the late-grazed paddock. During the pre-July period, soil moisture was depleted more rapidly in the upper- and mid-portions of the soil profile in ungrazed plots. By 25 September there was no difference in total soil water depletion ' through 53 cm between grazed and ungrazed treatments, but ungrazed plots extracted relatively more water in the mid- and lower-portions of the soil profile. Grazing had no effect on predawn leaf water potentials prior to 1 July, but predawn leaf water potentials were lower for ungrazed plants than for grazed plants after 1 July. Midday leaf water potentials were lower for grazed plants than for ungrazed plants before 1 July, but did not differ between grazed and ungrazed plants after 1 July. Time of grazing had no effect on either predawn or midday leaf water potentials.
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Roshani, Pedram. "The Effect of Temperature on the SWCC and Estimation of the SWCC from Moisture Profile under a Controlled Thermal Gradient." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31072.
Full textAbstract:
In many situations, the upper layers of soil above the ground water table are in a state of unsaturated condition. Although unsaturated soils are found throughout the world, they are predominant in arid or semi-arid regions. In these areas, the soil water characteristic curve (SWCC) which relates the water content to the matric suction could be used as key tool to implement the mechanics of unsaturated soils into the designs of geotechnical structures such as dams, embankments, pavements, canals, and foundations.
Several experimental techniques are available for determining the SWCC in a laboratory environment. However, these experimental techniques are expensive, time consuming typically requiring days or weeks, depending on the soil type, and demanding intricate testing equipment. Due to these reasons, there has been a growing interest to find other means for estimating SWCC and encourage the adoption of unsaturated soils mechanics in geotechnical engineering practice.
Several methods exist to indirectly estimate the SWCC from basic soil properties. Some may include statistical estimation of the water content at selected matric suction values, correlation of soil properties with the fitting parameters of an analytical equation that represents the SWCC, estimation of the SWCC using a physics-based conceptual model, and artificial intelligence methods such as neural networks or genetic programming.
However, many studies have shown that environmental effects such as temperature, soil structure, initial water content, void ratio, stress history, compaction method, etc. can also affect the SWCC. This means that the estimation SWCC from set of conditions may not reliably predict the SWCC in other conditions. Due to this reason, it is crucial for engineers involved with unsaturated soils to take into account all the factors that influence the SWCC.
The two key objectives of the present thesis are the development of a method based on first principles, using the capillary rise theory, to predict the variation of the SWCC as a function of temperature, as well as developing a technique for the prediction of the fixed parameters of a well-known function representing the SWCC based on basic soil properties together with the moisture profile of a soil column subjected to a known temperature gradient.
A rational approach using capillary rise theory and the effect of temperature on surface tension and liquid density is developed to study the relation between temperature and the parameters of the Fredlund and Xing (1994) equation. Several tests, using a Tempe cell submerged in a controlled temperature bath, were performed to determine the SWCC of two coarse-grained soils at different temperatures. A good comparison between the predicted SWCC at different temperatures using the proposed model and the measured values from the Tempe cell test results is achieved.
Within the scope of this thesis, a separate testing program was undertaken to indirectly estimate the SWCC of the same two coarse-grained soils from the measurement of their steady state soil-moisture profile while subjected to a fixed temperature differences. The water potential equation in the liquid and vapor phases is used to analyses the steady state flow conditions in the unsaturated soil. A good comparison is obtained for the SWCC estimated using this technique with the SWCC measured used a Tempe cell submerged in a controlled temperature bath.
The results of this study indicate that knowledge of the moisture content of a soil specimen under a constant thermal gradient and basic soil properties can be used to estimate the SWCC of the soil at the desired temperature.
34
Dolling, Perry. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia." University of Western Australia. Faculty of Natural and Agricultural Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.
Full textAbstract:
[Truncated abstract] In southern Western Australia the replacement of deep-rooted native vegetation with annual species has resulted in rising water tables and increased salinity due to insufficient water use. The area has a Mediterranean-type climate where rainfall during summer is generally low but variable resulting in limited plant growth. However, if rainfall does occur it potentially can contribute to to the increased water excess or drainage by increasing the soil water content before the main drainage period in winter. The first study investigated factors controlling soil water content changes during the fallow (December to May) in annual farming systems. This was achieved by examining variation in available soil water storage to a depth of 1.0-1.5 m at three sites within 13 seasons. Reasons for the variation were examined using the Agricultural Production Systems Simulator (APSIM). This study also investigated the relationship between soil water content at the end of the fallow period (1 May) and the amount of drainage below 2.5 m by using APSIM coupled to historical weather records at three locations. At the end of the fallow a mean of 24 mm (or 25%) of rainfall during the fallow was retained in the soil. Losses of soil water during the fallow were due to evaporation (mean of 60 mm), transpiration from plant cover (mean of 12 mm) and drainage below the root zone and run off (combined mean of 13 mm). Soil water accumulation during the fallow period had a significant impact on simulated drainage under wheat in the following growing season. Every 1 mm increase in soil wetness at the end of the fallow resulted in a 0.7-1 mm increase in simulated drainage during the growing season. ... Variation in the water excess due to variation in rainfall was greater than the reduction in water excess due to lucerne. This makes the decisions about when to grow lucerne to reduce water excess difficult if livestock enterprises are less profitable than cropping enterprises. The findings of this PhD indicate that lucerne does have a place in Mediterranean-type environments because of its greater water use than current farming practices. However, its use needs to be strategic and the strategy will vary from region to region. For example, in the low rainfall region lucerne sowings need to be matched with high soil water contents and phase length will generally be short (2-3 years). In comparison at high rainfall regions lucerne will need to be grown for longer or combined with other strategies to increase water use.
35
Rees, Stephen William. "Seasonal ground movement effects on buried services." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282492.
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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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Terrill, Thomas Howard. "Effects of soil moisture and al-nitrilotriacetate on yeild chemical composition and digestibility of ryegrass (Lolium multiflorum, L.) by meadow voles." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/53088.
Full textAbstract:
Flooding effects mineral composition of pasture grasses, but little is known concerning effects on mineral metabolism and fiber digestibility in animals. Experiments were conducted to investigate effects of flooding and Al-nitrilo-triacetate (Al-NTA) on growth, chemical composition and digestibility of annual ryegrass (Lolium multiflorum, L.). Ryegrass was grown in a greenhouse experiment on Bucks silt loam soil with two soil moisture levels (flooding and 80% field capacity) and two Al rates (0 and 135 mg/kg) as Al-NTA.
Flooding increased Al, Fe, Cu, Ca and fiber and decreased dry matter yield, Mg, K and Zn concentrations. Treatment with 135 mg/kg Al had no effect on Al in plants, but decreased Ca and P concentrations.
Two digestion trials were conducted with meadow voles (Microtus pennsylvanicus) fed forage harvested from the greenhouse experiment. Voles were housed in stainless steel metabolism cages for total collections of feed and feces. A 2-day preliminary, during which voles were fed 100% ryegrass, preceded a 3-day collection period. At the end of the collection period, a blood sample was taken from the animals.
Forage grown under flooding increased apparent absorption of Al, and Ca concentration in urine samples. Apparent absorption of Mg and serum Mg were decreased, and dry matter digestibility tended to decrease.
Grazing forages produced under flooded conditions would increase potential for outbreaks of grass tetany in animals due to reduced Mg intake and absorption. Altered Mg and Ca metabolism appeared related to Al ingestion. Lowered animal performance could result from reduced DM digestibility.<br>Master of Science
38
Shevelan, John. "Investigating the effects of heterogeneities on infiltration into unsaturated compacted soils." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369917.
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Sajedi, Toktam. "The effects of excessive moisture on soil carbon and nitrogen mineralization and forest productivity." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27030.
Full textAbstract:
Conifers of regenerating cedar-hemlock (CH) forests exhibit slow growth and nutrient deficiencies (N and P), which are not observed on adjacent cutovers of hemlock-amabilis fir (HA) forests. I test the theory that excessive moisture and resulting low oxygen availability in CH sites create the low N supply and poor growth in these ecosystems. A field experiment determined: 1) whether CH and HA forests differ in soil moisture and aeration, 2) whether decomposition rate and soil C stores differ in CH and HA forests, 3) whether composition of plant communities are related to soil moisture and aeration, and 4) the impact of harvesting CH and HA forests on moisture and aeration conditions. A laboratory experiment investigated the effects of moisture levels, from field capacity to saturation level, on C and N mineralization rates. Lastly, a field trial was carried out to assess drainage as a potential forest management solution in wetland forests by comparing C dynamics in drained and un-drained sites.
As hypothesized, CH forests were wetter, less aerated, had shallower aerated depth and higher frequency of anaerobic conditions compared with HA forests. Composition of plant species was related to soil moisture and aeration, however plant diversity was not. Soil aeration was the most important factor, explaining 25% of the variability of species within plant communities. Compared with HA forests with well-aerated soils, soils in HA clearcuts were anaerobic, had slower decomposition rate and shallower rooting depth. Microbial biomass, C mineralization and the soluble inorganic N: soluble organic N (SIN:SON) ratio all declined under water-saturated conditions. Concentrations of SIN increased with increasing moisture in HA soils; whereas in CH humus and soil, the SIN pool was small and decreased with increasing moisture. The results indicate that the low N availability on CH sites results from synergistic effects of litter quality and greater frequency of waterlogging. Drainage could be a useful silvicultural practice for improving the productivity of cedar-swamp ecosystems without stimulating loss of soil C, provided that redox levels are maintained at less than +300 mV, at which level oxygen is sufficient for plant growth but not for aerobic microbial decomposition.
40
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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Reed, Mickey Lynn 1952. "The effect of moisture stress and salinity on germination and growth of grain amaranth Amaranthus cruentus L and Amaranthus hypochondriacus L." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276777.
Full textAbstract:
The grain amaranths, Amaranthus cruentus and Amaranthus hypochondriacus have been promoted as grain-bearing plants of possible high productivity in saline or hot arid habitats. To investigate these claims, seeds of both species were germinated at 10, 15, 20, 25, 30, 35 and 40°centigrade. Germination percentage for both species was above 90% after four days at 20, 25, 30, and 35°C. Germination was negligible at 10 and 15°C and very low at 40°C. Seeds were germinated in isotonic solutions of PEG and NaCl at 0.0, -0.2, -0.4, -0.5, -0.6, -0.8, and -1.0 MPa osmotic potential at 30°C. Germination percentage was high in the range 0.0 to -0.4 MPa and dropped rapidly to zero in the -0.6 to -1.0 MPa range. Differences due to chemical effects were significant. Species differences were not. Radicles and hypocotyls were measured after six days in the above media. PEG was more inhibitory of seedling growth than was NaCl and generally inhibited A. cruentus more than A. hypochondriacus. This was also true of NaCl. All growth functions were slightly inhibited at 0.0 to -0.4 MPa and very inhibited above -0.6 MPa. PEG radically increased root/shoot ratio in both species.
42
Jordan, Kyle K. "The effects of landscaping mulch on invertebrate populations and soil characteristics." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1092784271.
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Day, A. D., and K. L. Ludeke. "Effects of Soil Materials, Mulching Treatments, and Soil Moisture on the Growth and Yield of Western Wheatgrass for Coal Mine Reclamation." University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/554234.
Full textAbstract:
A 3-year experiment was conducted in the greenhouse at Tucson, Arizona to study the effects of three soil materials, three mulching treatments, and two soil moisture treatments on the growth and forage production of western wheatgrass (Agropyron smithii Rydb.) when used in the reclamation of coal mine spoil. The three mulching treatments were: (1) No mulch. (2) Barley (Hordeum vulgare L.) straw mulch, and (3) Russian thistle (Salsola kali L.) mulch. The two soil moisture treatments consisted of: (1) Optimum (60 cm total) and (2) Stressed (30 cm total). There were significant differences in number of stems per pot, plant height, and forage yield between soil materials, mulching treatments, and soil moisture treatments. The Gila loam soil, barley straw mulch, and optimum soil moisture treatment produced the highest number of stems per plot, the tallest plants, and the highest yield of forage. Plants were more vigorous and produced more forage when soil mulch (incorporated organic matter mulch) was used than when soils were not mulched. Barley straw and Russian thistle were of similar value as mulching materials. Within soil materials and within mulching treatments forage yields were significantly higher with optimum soil moisture than they were when moisture was limited.
44
Williams, Todd Joseph. "Effects of temperature and moisture content on transport of organic vapours in dual-porosity soil." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0025/MQ50379.pdf.
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Dikinya, Oagile. "The effects of self-filtration on saturated hydraulic conductivity in sodic sandy soils /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0051.
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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.
Full textAbstract:
Thesis (MScAgric)--University of Stellenbosch, 2001.<br>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.<br>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.
47
Lower, Steven S. "The effects of soil nutrients and water on the suitability of silky willow for the imported willow leaf beetle /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2002.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 2002.<br>Adviser: Colin M. Orians. Submitted to the Dept. of Biology. Includes bibliographical references (leaves 111-127). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
48
Bisso, Eya Joseph 1955. "The effects of maturity differences on competition between adjacent rows of Sorghum bicolor varieties at two levels of soil moisture." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276972.
Full textAbstract:
The objective of the study was to determine if and how grain sorghum hybrids (Sorghum bicolor (L.) Moench) of different maturity dates compete with one another when planted in adjacent rows under different moisture levels. Five sorghum varieties differing in their maturity were used: Taylor Evans Y-101-G coming to mid-bloom in 71 days, RS 610, Asgrow Corral, DK 64 and DK 69 coming to mid-bloom in 56.9 days, 61 days, 69.3 days and 75.6 days respectively. Six agronomic characters were measured to determine the effect and extent of competition. They included the number of days to mid-bloom, tiller ratio, grain yield, grain test weight and 300-seed weight. According to the results, adjacent row competition took place due to differences in maturity date for grain yield and 300-seed weight. An almost equilibrium appeared between loss or gain of border rows compared to the loss or gain of the middle row. Also the length of time between day to mid-bloom of the border rows hybrids and the center row genotype was important in the extent of competition effects.
49
Lagergren, Fredrik. "Effects of thinning, weather and soil moisture on tree and stand transpiration in a Swedish forest /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/avh/2001/91-576-6315-7.pdf.
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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.
Full textAbstract:
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.