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1
Carminati, Andrea. "Unsaturated water flow through soil aggregates /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17011.
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Walworth, James. "Using Gypsum in Southwestern Soils." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/144801.
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Walworth, James. "Using Gypsum and Other Calcium Amendments in Southwestern Soils." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2012. http://hdl.handle.net/10150/246053.
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Liang, Yun [Verfasser]. "Emerging threats to the stability of soil aggregates / Yun Liang." Berlin : Freie Universität Berlin, 2021. http://d-nb.info/1234451573/34.
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Okunlola, A. "Mechanics of breakdown of soil aggregates under static loading and impact." Thesis, University of Reading, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373750.
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Cincotta, Malayika. "Soil Aggregates: The mechanistic link to increased dissolved organic carbon in surface waters?" ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/961.
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Dissolved organic carbon (DOC) plays an important role in the global carbon (C) cycle because increases in aqueous C potentially contribute to rising atmospheric CO2 levels. Over the past few decades, headwater streams of the northern hemisphere have shown increased amounts of DOC coinciding with decreased acid deposition. Although the issue is widely discussed in the literature, a mechanistic link between precipitation composition and stream water DOC has not yet been proposed.
In this study, the breakup of soil aggregates is hypothesized as the mechanistic link between reduced acid deposition and DOC increases in surface waters. Specific hypotheses state that soil aggregate dispersion (and the ensuing release of DOC from these aggregates) is driven by a decrease in soil solution ionic strength (IS, decreasing the tendency of flocculation) as well as a shift from divalent to monovalent cations (reducing the propensity for cation bridging) in soil solution.
These hypotheses were tested on soil samples collected from several riparian zone and hillslope positions along three flagged transects in the acid-impacted Sleepers River Research Watershed in northeastern Vermont. To determine soil C content by landscape position, samples from transects spanning hilltop to hillslope and riparian area, as well as replicated hillslope and riparian samples (n=40) were analyzed. Aqueous soil extracts simulate the flushing of soils during hydrologic events (e.g. rain or snowmelt) and were used to test the effect of soil solution chemistry on DOC release. Extracts were prepared with solutions of varying IS (0-0.005M) and composition (CaCl2 and NaCl) on replicated soil samples (n=54) and changes in DOC release and aggregate size were monitored. As IS of the extraction solution increased, the amount of DOC in solution decreased, and aggregate size increased. This was presumably due to cations bridging and diffuse double layer effects. This effect was reversed in low ionic strength solutions where DOC release was significantly higher and average aggregate size was smaller. While extraction solution controlled the amount of C liberated, landscape position impacted the quality, but not quantity, of released DOC.
This study is the first to propose a mechanistic link observed changes in DOC in surface waters and recovery from acidification and provides initial experimental evidence that soil aggregates indeed play a role in the generation of DOC.
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Chacón, Montes de Oca Paula. "Effect of Land Use, Climate and Soil Structure on Soil Organic Carbon in Costa Rican Ecoregions." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1252995403.
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Nebo, Godwin Iloabuchi. "Soil aggregates characteristics and interrill erosion in some weakly weathered coarse textured ecotopes in Eastern Cape Province, South Africa." Thesis, University of Fort Hare, 2013. http://hdl.handle.net/10353/d1004351.
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Aggregate stability and aggregate size distribution on soil surface that is impacted by rain drops affect soil erosion yet little is known about less weathered coarse textured soils. The objectives of the current study were to determine (i) the aggregate stability and associated aggregate fraction size distribution and (ii) the impact of the initial aggregate size on the aggregate stability and the resulting sediment fraction size distribution following rain drop impact in some quartz dominated coarse textured soils in the Eastern Cape Province. Soil samples for this experiment were collected from 14 ecotopes on the surface with a natural slope between 7.5 to 11% and at the depth between 0 to 0.2 m in the Eastern Cape Province. In each ecotope, twenty-five different spots were sampled using a spade at depth 0 to 0.2 m in other to eradicate biasness and ensure homogeneity. Thereafter, the soil samples were mixed to make a composite sample. The composited soil samples were then placed in rigid containers and taken to the soil science laboratory of the University of Fort Hare, Alice Campus where analyses were carried out. The soil properties were determined by passing the < 5 mm soil sample through a 2 mm sieve. The total Na, Ca and Mg contents in the soil samples were also determined using the wet digestion with sulphuric acid method. The total Soil organic matter content (SOM) was determined by the process known as weight loss on ignition. Thereafter, the fraction size distribution and aggregate stability was done by passing < 5 mm soil samples through a 3 mm sieve. The obtained calibrated aggregates between 3 and 5 mm were oven dried at 40o C. Thereafter, five gram (5g) of oven dried calibrated aggregates was immersed in a 50 mL deionized water in a 250 mL beaker for 10 minutes. The soil material left was transferred to a 0.053 mm sieve already immersed in ethanol and moved five times in the ethanol to separate < 0.053 mm from > 0.053 mm fragments. The remaining > 0.053 mm was re-immersed in ethanol and further oven dried at 40o C for 5 minutes. Thereafter, the > 0.053 mm fraction was transferred from 0.053 mm sieve, oven dried at 40o C, dry sieved using Digital Electromagnetic Shaker on a six column of sieves: 2 mm, 1 mm, 0.5 mm, 0.25 mm, 0.106 mm, and 0.053 mm. The aggregate stability was determined using the resulting size distribution in seven classes by calculating the mean weight diameter (MWD, mm). The soils were very stable, moderately stable or unstable. The presence of smectite and cultivation as opposed to pasture lowered aggregate stability. The studied soils showed three different aggregate size distributions. Unstable soils were dominated by 0.106 – 0.25 mm aggregate size and showed a positively skewed aggregate fraction size distribution. Aggregates finer than 0.106 mm were limited because of the coarse nature of the soil texture. Moderately stable soils broke down to both micro aggregates, 0.106 – 0.25 mm and macro aggregates, 2 – 5 mm giving a bimodal distribution. The aggregate size distribution in the very stable soils was dominated by the aggregate fraction size 2 – 5 mm and a negatively skewed aggregate fraction size distribution. The smaller the initial aggregate size the higher was the aggregate stability but the reverse was true for splash erosion. It was thought that the short 5 minutes duration of the rainfall might not have been enough to cause a total breakdown of the aggregates. Alternatively, ecotopes that were dominated by primary soil minerals such as quartz showed different breakdown behaviour compared to those containing secondary minerals such as kaolinite or smectite.
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Gumbert, Amanda A. "INFLUENCE OF RIPARIAN BUFFER MANAGEMENT STRATEGIES ON SOIL PROPERTIES." UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/27.
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The Kentucky Division of Water indicates that agriculture is responsible for 55% of the Commonwealth’s assessed streams not supporting their designated uses. Riparian buffers reduce nonpoint source pollution in agroecosystems by storing and cycling nutrients, stabilizing streambanks, increasing infiltration, and storing water. Specific information regarding riparian buffer management is needed for land managers to maximize buffer effectiveness at reducing agricultural contaminants impairing water quality.
Baseline soil properties (texture, pH, C and nutrients) of the riparian buffer surrounding a tributary of Cane Run Creek in Fayette County, KY were characterized prior to imposing three mowing regimes (intense, moderate, and no mow treatments) and one native grass regime. Measurements were made along parallel transects located 2-m and 8-m distances from the stream. Root biomass, aggregate distribution, and saturated hydraulic conductivity were measured along the 2-m transect in two consecutive years following treatment establishment. The 2-m transect soils had the highest C, pH, Ca, Zn, and sand content. The 8-m transect had the highest P, K, Mg, and clay content. Semivariogram analysis of C content indicated slight to moderate spatial dependency along the 2m transect and moderate to strong spatial dependency along the 8m transect. Root biomass increased with decreased mowing frequency at the surface depth after one year; the native grass treatment had significantly less root biomass in both years compared to mowing treatments. There was no significant treatment effect on aggregate size distribution at the surface depth in either year. Mean weight diameter and large macroaggregates decreased from 2011 to 2012. Vegetation treatment had no statistically significant effect on water stable aggregates or saturated hydraulic conductivity. Experimental semivariograms provided evidence of spatial structure at multiple scales in root biomass, aggregates, and soil C. Spatial variability occurred over a shorter lag distance in 2012 than 2011, suggesting an effect of imposed treatments slowly developing over time.
This study provides important insights on riparian buffer soil properties, soil sampling strategies to detect spatial variability in riparian buffers, and length of time needed to assess effects of vegetation management regimes on riparian root biomass, soil aggregates, and hydraulic conductivity.
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Asmus, Chad Donald. "Soil aggregation and carbon sequestration following a single tillage event in no-till soils in a semi-arid environment." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1405.
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Wacha, Kenneth Michael. "From soilscapes to landscapes: a landscape-oriented approach to simulate soil organic carbon dynamics in intensely managed landscapes (IMLS)." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/6327.
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The primary objective of this research was to develop a landscape-oriented, process-based approach that can enhance understanding and prediction of SOC fluxes in IMLs by incorporating the key mechanisms impacting soil carbon dynamics when moving from the soilscape to the landscape. The mechanisms that are considered to be the focus of this study are redistribution of SOC due to erosion and deposition without neglecting the importance of litter incorporation into the soil column, decomposition due to microbial activity, and physical and chemical stabilization of carbon. To accomplish this objective, field experiments were performed to examine how selective entrainment of different soil size fractions, quantified through the enrichment ratio (ER), varies with management and hillslope position. Differential modes in soil mobilization between rill and interrill areas were either elevated or dampened depending on the prevalent management practice, the gradient of the site and landscape position. Sites where sediment and runoff fluxes were highest were found to have lower ER values (around unity) due to the mobilization of all size classes making static and dynamic samples almost identical.
The size fractions analyzed in these experiments were found to have varying levels of carbon associated with them, especially the larger aggregates, which encapsulate organic material. Neglecting them in transport estimates could lead to large errors in predicted fluxes of SOC. For this reason, a careful attention was placed on identifying how aggregate stability varies with respect to management and hillslope position, through controlled experiments looking size distributions to reflect tillage disturbance and aggregate stability to assess resistance to rainsplash.
Lastly, a landscape-oriented modeling framework was developed that captures not only the SOC spatial heterogeneity in IMLs but also determines the impacts that redistribution has on this heterogeneity and ultimately on SOC dynamics. The integrative modeling framework considers the collective effects of both rainsplash/rainfall- and tillage-induced erosion on SOC redistribution in IMLs through an ER-module developed and woven within this framework to connect an upland erosion model with a soil biogeochemical model. It provides not only size fraction updates to the active layer and ER values, but also explicitly considers the effects of splash-driven interrill erosion on those ER estimates.
The model was applied to twentieth-century changes in SOC across a representative agricultural hillslope in the study watershed and compared to recent SOC data. The chronosequence in SOC storage within the erosional zone revealed that soils were continually depleted of the rich organic matter long after the 1930’s “Dust bowl” due to enhanced erosion that accompanied agricultural practices. However, conservation tillage and enhanced crop production that began in the late 1980’s reversed the downward trend in SOC losses, causing nearly 26% of the lost SOC to be regained. Results from this study can be used to aid policy and decision makers in developing a food-system that accounts for the co-evolution of human and natural activity, to develop sustainable agro-ecosystems through the use of data supported recommended best management practices.
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Smith, Katie Elizabeth. "The nature, distribution and significance of organic carbon within structurally intact soils contrasting in total SOC content." Thesis, University of Stirling, 2010. http://hdl.handle.net/1893/2915.
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Soil structure influences many chemical, biological and physical processes and it is well established that organic carbon acts as a soil binding agent. However, the precise location of organic matter and carbon in relation to structural features within intact samples is unknown. The sensitivity of organic carbon to decomposition is dependent not only upon its intrinsic chemical recalcitrance, but also its location within the soil structure. Soil structure provides organic carbon with chemical and physical protection, the extent of which varies between structural units. Furthermore soil structure is transient, and is sensitive to both environmental changes and physical disturbance, therefore it is difficult to determine and quantify the impact of this dynamic entity upon the storage of organic carbon. To date the majority of research that has advanced our understanding of the role soil structure plays in the storage of organic carbon, has relied upon some form of fractionation technique to separate aggregates from the bulk soil. However this approach has its disadvantages as much of the soil structure is destroyed; clearly when studying the impact of soil structure upon organic carbon-storage it is advantageous to implement any method that minimises disturbance to the soil structure. This study entails removing intact soil samples (through the use of kubiena tins) from long-term agricultural experimental fields at Rothamsted Research, (Hertfordshire, UK) with the aim of comparing and evaluating the location of organic matter and it’s associated organic carbon, in soils with contrasting organic carbon contents and a well documented land-use history. Thin sections will be analysed by integrating conventional micromorphology, image analysis and sub-microscopy combined with microscale chemical analysis scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). In doing so a new alternative method for analysing the distribution of organic matter and organic carbon is proposed. It was found that agricultural soils, which are the same in all aspects except total-OC content, differ in total organic matter, water release characteristics, aggregate stability and pore size distribution; therefore these differences could be attributed to the relationship between OC and soil structure. The water release curve, aggregate stability and pore size distribution also differed between soils with similar OC-contents but from different land-uses. The analysis of organic matter within intact soil samples provided evidence for the redistribution of organic matter as it is decomposed within the soil structure, for instance, less decomposed organ and tissue forms were located in or near to soil pores while more decomposed amorphous forms were located within the soil matrix. Since the same pattern of redistribution was observed in both agricultural and grassland soil this is likely to be directed by soil macro and micro fauna. It is concluded that since the location of different forms of organic matter is consistent across all soil, organic matter location is not responsible for creating differences in aggregate stability between treatments. Instead the results indicate that the amount and strength of organic carbon bonds and its hydrophobic properties are responsible. Micromorphology results demonstrated an absence of defined aggregation between treatments. Despite the difficulties in the interpretation of aggregation, the results contradict theories of aggregation, which state that aggregates are formed around “fresh” organic matter and it is argued that OM will undergo substantial decomposition before it acts as core for aggregation. Initial SEM-EDS analysis, has shown that in the soil matrix adjacent to organic matter (plant/organ) fragments there is a heightened concentration of C, indicating that these fragments are acting as a source of organic carbon. Interestingly BC, which represent one of the most recalcitrant C forms is also acting as a source of C, although these initial results suggest to a lesser extent than more labile C-sources. This source of organic carbon could stimulate microbial activity thereby enhancing soil structural stability. Alternatively, the release of liable carbon into soil pores may represent one route by which labile carbon enters sub-soil horizons.
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Jasinska, Emilia. "Management effects on carbon distribution in soil aggregates and its consequences on water repellency and mechanical strength." kostenfrei, 2006. http://e-diss.uni-kiel.de/diss_1706/d1706.pdf.
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Hossler, Katie. "Accumulation of Carbon in Created Wetland Soils and the Potential to Mitigate Loss of Natural Wetland Carbon-Mediated Functions." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1239285185.
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Simonetti, Gianluca. "Mechanisms of soil organic matter protection and sequestration." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3422238.
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Soil organic carbon (SOC) protection processes have received much interest recently due to the possibility to enhance the carbon sink in agricultural soils with atmospheric CO2 reduction purposes. Further knowledge of these mechanisms is thus fundamental to promote effective C sequestration practices in terrestrial sinks, as recognized by Article 3.4 of the Kyoto Protocol. In a long-term experiment established in the early 1960s in north-eastern Italy, we used a combination of physical fractionation and chemical extraction techniques aiming to isolate homogeneous pools of SOC. In particular we wet-sieved large macroaggregates into three aggregate-size classes (2000-250 μm, 250-53 μm and <53 μm) in contrasting soils (clay, sandy and peaty) fertilized with manure or mineral fertilizers. We analyzed the organic (OC) and humic (HC) carbon of each aggregate fraction, the molecular weight of the humic substances (HS) extracted, the HS functional groups by NMR and DRIFT spectroscopy and the porosity of the different aggregate fraction by MIP (Mercury Intrusion Porosimetry). The aims were to evaluate the protection processes in the different SOC pools isolated analyzing the effect of the different fertilization types on the aggregates, the organic matter distribution and to investigate the composition and role of HC as binding agent. The thesis is structured in four chapters. The first chapter is a review on the SOC topic, its protection processes and the analytical methods for its study. The second chapter focuses on aggregate distribution, OC, HC, HS gel filtration and the rule of HC as persisting binding agent. The third chapter had a qualitative description of C functional groups (NMR-DRIFT) in HS extracts from the different aggregate fractions. The final chapter had the correlation between the porosity of the different aggregate fractions and the different parameters measured in chapter II and III.I meccanismi di protezione del carbonio organico del suolo rappresentano un argomento di grande attualità poiché, attraverso di essi, si esplica l'azione di carbon sink indicata nelle politiche volte alla mitigazione dell'effetto serra. Una maggior conoscenza di questi processi è quindi fondamentale per promuovere strategie di sequestro efficaci, così come previsto dall'articolo 3.4 del protocollo di Kyoto. Per realizzare lo studio è stato effettuato,a partire da macroaggregati prelevati da una prova di lungo periodo, un frazionamento degli aggregati stabili all'acqua con l'obiettivo di isolare dei pool di carbonio omogenei e riconducibili a specifici meccanismi di stabilizzazione. Sono stati frazionati in questo modo differenti suoli (argilloso, torboso e sabbioso) trattati con letame e con fertilizzanti minerali, ottenendo tre classi di aggregati (2000-250 μm, 250-53 μm and <53 μm). È stato quindi determinato, per i diversi aggregati, il carbonio organico (OC) e umico (HC), le frazioni umiche a diverso peso molecolare (HS), i gruppi funzionali presenti nelle sostanze umiche (spettroscopia NMR e DRIFT) e la porosità degli aggregati (porosimetria a intrusione di mercurio MIP). L'obiettivo è stato quello di valutare l'effetto delle differenti tesi sull'aggregazione e sulla distribuzione del carbonio organico, nonché valutare il ruolo delle sostanze umiche quali agenti leganti persistenti. Più in generale si è cercato di studiare quali meccanismi di protezione governano le diverse frazioni di aggregati. La tesi è stata strutturata in quattro capitoli; il primo capitolo è una review sul carbonio organico del suolo, i suoi meccanismi di protezione e le relative tecniche di analisi. Il secondo capitolo è dedicato alla distribuzione del carbonio organico e umico negli aggregati, delle frazioni umiche a diverso peso molecolare nonché del ruolo del carbonio umico come agente legante persistente. Il terzo capito è incentrato sull'analisi qualitativa degli estratti umici dei diversi aggregati sulla base dei gruppi funzionali rilevati dall'analisi NMR e DRIFT. Il quarto capitolo analizza le correlazioni fra la porosità dei diversi aggregati e le caratteristiche quali-quantitative del carbonio umico.
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Pandey, Ganesh. "Feasibility Study of Water Based / Polymer Modified EICP for Soil Improvement Involving Recycled Glass Aggregate." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron153115070027817.
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Bobe, Bedadi Woreka. "Evaluation of soil erosion in the Harerge region of Ethiopia using soil loss models, rainfall simulation and field trials." Thesis, University of Pretoria, 2004. http://hdl.handle.net/2263/26929.
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Accelerated soil erosion is one of the major threats to agricultural production in Ethiopia and the Harerge region is not exceptional. It is estimated that about 1.5 billion tones of soil is being eroded every year in Ethiopia. In the extreme cases, especially for the highlands, the rate of soil loss is estimated to reach up to 300 t ha-1yr-1 with an average of about 70 t ha -1yr-1 which is beyond any tolerable level. The government have made different attempts to avert the situation since 1975 through initiation of a massive program of soil conservation and rehabilitation of severely degraded lands. Despite considerable efforts, the achievements were far bellow expectations. This study was aimed at assessing the effect of some soil properties, rainfall intensity and slope gradients on surface sealing, soil erodibility, runoff and soil loss from selected sites in the Harerge region, eastern Ethiopia, using simulated rainfall. Soil loss was also estimated for the sites using Soil Loss Estimation Model for Southern Africa (SLEMSA) and the Universal soil Loss Equation (USLE). Moreover, the effectiveness of various rates and patterns of wheat residue mulching in controlling soil loss was also evaluated for one of the study sites, (i.e. Regosol of Alemaya University), under both rainfall simulation and field natural rainfall conditions. For most of the erosion parameters, the interaction among soil texture, slope gradient and rainfall intensity was significant. In general however, high rainfall intensity induced high runoff, sediment yield and splash. The effect of slope gradients on most of the erosion parameters was not significant as the slope length was too small to bring about a concentrated flow. The effect of soils dominated by any one of the three soil separates on the erosion parameters was largely dependent on rainfall intensity and slope gradient. The soils form the 15 different sites in Harerge showed different degrees of vulnerability to surface sealing, runoff and sediment yield. These differences were associated with various soil properties. Correlation of soil properties to the erosion parameters revealed that aggregate stability was the main factor that determined the susceptibility of soils to sealing, runoff and soil loss. This was in turn affected by organic carbon content, percent clay and exchangeable sodium percentage (ESP). Soils with relatively high ESP such as those at Babile (13.85) and Gelemso (7.18) were among the lowest in their aggregate stability (percent water stable aggregates of 0.25 –2.0mm diameter); and have highest runoff and sediment yield as compared to other soils in the study. Similarly, most of those soils with relatively low ESP, high organic carbon content (OC%) and high water stable aggregates such as Hamaressa, AU (Alemaya University) vertisol and AU regosol were among the least susceptible to sealing and interrill erosion. Nevertheless, some exceptions include soils like those of Hirna where high runoff was recorded whilst having relatively high OC%, low ESP and high water stable aggregates. Both the SLEMSA and USLE models were able to identify the erosion hazards for the study sites. Despite the differences in the procedures of the two models, significant correlation (r = 0.87) was observed between the values estimated by the two methods. Both models estimated higher soil loss for Gelemso, Babile, Karamara and Hamaressa. Soil loss was lower for Diredawa, AU-vertisol and AU-Alluvial all of which occur on a relatively low slope gradients. The high soil loss for Babile and Gelemso conforms with the relative soil erodibility values obtained under rainfall simulation suggesting that soil erodibility, among others, is the main factor contributing to high soil loss for these soils. The difference in the estimated soil losses for the different sites was a function of the interaction of the various factors involved. Though the laboratory soil erodibility values were low to medium for Hamaressa and Karamara, the estimated soil loss was higher owing to the field topographic situations such as high slope gradient. SLEMSA and USLE showed different degrees of sensitivities to their input variables for the conditions of the study sites. SLEMSA was highly sensitive to changes in rainfall kinetic energy (E) and soil erodibility (F) and less sensitive to the cover and slope length factors. The sensitivity of SLEMSA to changes in the cover factor was higher for areas having initially smaller percentage rainfall interception values. On the other hand, USLE was highly sensitive to slope gradient and less so to slope length as compared to the other input factors. The study on the various rates and application patterns of wheat residue on runoff and soil loss both in the laboratory rainfall simulation and under field natural rainfall conditions revealed that surface application of crop residue is more effective in reducing soil loss and runoff than incorporating the same amount of the residue into the soil. Likewise, for a particular residue application method, runoff and soil loss decreased with increasing application rate of the mulch. However, the difference was not significant between 4 Mg ha-1 and 8 Mg ha-1 wheat straw rates suggesting that the former can effectively control soil loss and can be used in areas where there is limitation of crop residues provided that other conditions are similar to that of the study site (AU Regosols). The effectiveness of lower rates of straw (i.e. less than 4 Mg ha-1 ) should also be studied. It should however be noted that the effectiveness of mulching in controlling soils loss and runoff could be different under various slope gradients, rainfall characteristics and cover types that were not covered in this study. Integrated soil and water conservation research is required to develop a comprehensive database for modelling various soil erosion parameters. Further research is therefore required on the effect of soil properties (with special emphasis to aggregate stability, clay mineralogy, exchangeable cations, soil texture and organic matter), types and rates of crop residues, cropping and tillage systems, mechanical and biological soil conservation measures on soil erosion and its conservation for a better estimation of the actual soil loss in the study sites. Copyright 2004, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bobe, BW 2004, Evaluation of soil erosion in the Harerge region of Ethiopia using soil loss models, rainfall simulation and field trials, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-08022004-141533 / >Thesis (PhD (Soil Science))--University of Pretoria, 2004.
Plant Production and Soil Science
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Mitton, Rolff Vladimir. "Mineralogy and potassium mineral reserve in different soil aggregates classes and the levels of this nutrient in wheat (Triticum aestivum)." reponame:Repositório Institucional da UFPR, 2017. http://hdl.handle.net/1884/49376.
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Orientador: Prof. Dr. Vander de Freitas MeloCoorientador: Prof. Dr. Volnei Pauletti
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Programa de Pós-Graduação em Ciência do Solo. Defesa: Curitiba, 26/04/2017
Inclui referências : f. 60-67
Resumo: A biodisponibilidade do K em suas diferentes formas minerais é muito variável e depende de vários fatores (concentração na solução do solo, capacidade de troca catiônica (CTC), grau de intemperismo do solo, etc.) que influenciam o equilíbrio químico do nutriente dentro do solo. O objetivo do presente trabalho foi estudar a dinâmica das diversas formas minerais do Potassio (K) em diferente classes de agregados de solos jovens (Cambissolo) e altamente intemperizados (Latossolo), desenvolvidos a partir de granito/gnaisse e basalto respetivamente na mineralogia do solo e avaliar a importancia da reserva do K na nutrição das plantas de trigo. Para este estudo, foram consideradas duas classes de solo da taxonomia brasileira do solo, um CAMBISSOLO HAPLICO Tb distrófico e um LATOSSOLO VERMELHO Distroférrico tipico. Ambos os solos foram separados em tamanho de agregados; o Latossolo em 5 (> 4 mm, 2 - 4 mm, 0,5 - 2 mm, 0,21 - 0,5 mm e < 0,21 mm) e o Cambissolo em 4 (> 4 mm, 2-4 mm, 0,5-2 mm e < 0,5 mm). Diferentes formas de K foram determinadas em cada tamanho de agregado em ambos os solos e essas formas no solo foram correlacionadas com a absorção de K por plantas de trigo. Em cada classe de agregado tambem foi estudada a mineralogia das frações areia, silte e argila. Foi cultivado o trigo separadamente nas diferentes classes de agregados e após a colheita das plantas, os teores de K foram determinados na parte aérea e nas raizes. A fração argila do Cambissolo apresentou a predominancia da caulinita altamente cristalizada, enquanto no Latossolo, os minerais predominantes foram a gibbsita e a hematita com grau de cristalinidade moderado a alto. Houve pequena variação entre os agregados de cada solo quanto a mineralogia da fração argila. O K trocável pela extração de Mehlich-1, foi identificado como a forma mineral de K mais preditiva da disponibilidade deste nutriente no trigo. As formas não-trocáveis de K, tanto pelo HNO3 como pelo HF, refletiram a natureza do material de origem do Cambissolo (granito/gnaisse) e do Latossolo (basalto). O K não-trocável tambem contribuiu para a nutrição do trigo, variavél em função do tamanho do agregado. Para o Cambissolo esta contribuição ocorreu apenas nos maiores tamanho de agregados (> 4 mm e 4 - 2 mm), enquanto para o Latossolo a contribuição foi observada em todos os tamanhos de agregados. Palavras-chave: nutrição de plantas, formas de K, mineralogia.
Abstract: The bioavailability of K in its different mineral forms is very variable and depends on several factors (concentration in the soil solution, cation exchange capacity (CEC), degree of soil weathering, etc.) that influence the chemical balance of the nutrient within the soil. The objective of the present study was to study the dynamics of the different mineral forms of K in various aggregates size in young (Inceptisol) and highly weathered (Oxisol) soils in the State of Paraná, Brazil, developed respectively from granite / gneiss and basalt in soil mineralogy, and to evaluate the importance of the K reserve in the nutrition of wheat plants. For this study, two soil classes were considered: an Inceptisol and an Oxisol. Both soils were separated into aggregate size; the Oxisol in 5 classes (> 4 mm, 2 - 4 mm, 0.5 - 2 mm, 0.21 - 0.5 mm, and < 0.21 mm) and the Inceptisol in 4 classes (> 4 mm, 2 - 4 mm, 0.5 - 2 mm, and < 0.5 mm). Different K forms were determined in each aggregate size in both soils and these soils were correlated with K uptake by the wheat plants. In each class of aggregate was also studied the mineralogy of the sand, silt and clay fractions. The wheat was grown separately in the different classes of aggregates, and after the plants were harvested, the K contents were determined in the aerial part and in the roots. The clay fraction of the Inceptisol showed the predominance of highly crystallized kaolinite, while in the Oxisol, the predominant minerals were gibbsite and hematite with a moderate to high degree of crystallinity. There were small variations between the aggregates of each soil in relation to the mineralogy of the clay fraction. The exchangeable-K extraction by the Mehlich-1, was found to be the most predictive form of K for the availability of this nutrient in wheat. The non-exchangeable (HNO3 1 mol L-1) and total (HF concentrated) K forms, reflected the nature of the parental material for the Inceptisol (granite/gneiss) and the Oxisol (basalt). The non-exchangeable K also contributed to the wheat nutrition, which varied according to the size of the aggregate. For the Inceptisol, this contribution occurred only in the greater aggregates sizes (> 4 mm and 4 - 2 mm), while for the Oxisol, the contribution was observed in all the aggregate sizes. Keywords: Plant nutrition, K forms, mineralogy.
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Holsinger, John Frederick. "The Impact of SMCRA on Select Soil Properties in Reclaimed Mine Sites Determined by Geochemical and Hydrological Analyses." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406134738.
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Dias, João Fernando. "Avaliação de resíduos da fabricação de telhas cerâmicas para seu emprego em camadas de pavimento de baixo custo." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-16122004-130717/.
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Este trabalho apresenta a análise de agregados reciclados de telhas de cerâmica vermelha, visando seu emprego em camadas de pavimentos de baixo custo, baseado em estudos de laboratório. A indústria de cerâmica vermelha gera refugos da queima que são tratados como resíduos, mas se constituem em materiais de alto conteúdo energético e matéria prima de qualidade. O quadro da geração desses resíduos foi diagnosticado nas cidades de Monte Carmelo e Ituiutaba, em Minas Gerais. Os dados quantitativos obtidos indicam que é justificável a sua reciclagem. Somente na cidade de Monte Carmelo, as quantidades geradas permitiriam executar 10,8 km de camada de base de pavimento, ao se misturar 40% de solo poderia atingir 32 km por ano. Aproximadamente 10 t destes resíduos foram britadas obtendo-se o agregado reciclado de telha (ART). Estes agregados foram caracterizados mediante os ensaios físicos e mecânicos, e submetidos aos ensaios empregados na pavimentação, como a metodologia tradicional, metodologia MCT, método da pastilha, resistência ao cisalhamento, outros ensaios denominados índices de qualidade, ensaio de módulo resiliente e deformação permanente. Apesar deste material atender aos principais requisitos da metodologia tradicional, identificou-se que ele quebra com a aplicação de energia de compactação e de tensões nos ensaios, e apresenta alta resiliência - grandes deformações resilientes-, o que levaria à perda da capacidade de suporte da estrutura do pavimento, por fadiga. Desenvolveu-se uma metodologia para a determinação da absorção no estado saturado superfície seca, de agregados porosos, com fração fina inclusive, pois os métodos conhecidos não são aplicáveis; esta metodologia pode ser aprimorada para se constituir em norma de ensaio. Estudou-se um método inédito para a otimização do volume compactado da mistura de agregado com solo, baseado na porosidade do material granular, como uma alternativa ao método da estabilização granulométrica que se mostrou inadequado, no caso. As misturas produzidas com solos lateríticos foram avaliadas após a compactação não apresentando mais a quebra dos grãos do agregado, e mostraram ganhos expressivos no valor do módulo de resiliência, chegando em um caso a atingir 288% acima do módulo do agregado. Os resultados dos ensaios de laboratório indicaram ser possível a aplicação deste material em misturas com solos lateríticos, em camadas de pavimentos de baixo custo.The purpose of this work is to use recycled aggregate of ceramics roofing tiles for low cost pavement layers, based on laboratory studies. The heavy-clay ceramic industry generates wastes, originated from the calcination stage, that are considered as residues which demand resources for its deposition. However they are high energy content materials which can be useful. The generation of these residues in the cities of Monte Carmelo and Ituiutaba, in the State of Minas Gerais indicated that its recycling is valid. For instance, in the city of Monte Carmelo, it is generated such a large amount of residues that it should be enough to execute about 10,8 km of base course of pavement; moreover if 40% of soil is mixed 32 km pavement per year can be produced. For this study, approximately 10 metric tones of these residues had been crushed to produce the recycled aggregate from roofing tile. The aggregates produced had been characterized by physical and mechanical tests. They were also submitted to the tests used for aggregates for pavement, such as the traditional methodology, methodology MCT (tropical compacted miniature), shear strength, resilient module, permanent deformation, and other tests called quality rates. These residues comply with the main requirements of the traditional methodology, however it is necessary to point out that the material breaks with the application of energy for compaction and under the tensions during the mechanical tests, it also presents high resilience, or great resilient deformations, which will lead to the loss of the supporting capacity of the pavement due to fatigue. An appropriate methodology was developed for the porous aggregate absorption measurement, including its fraction, in the saturated dry surface state. As the known methods for absorption are not applicable, this methodology with improvements can be proposed as standard test. A new method to optimize the compacted volume of the mixture was studied, based on the porosity of the granular material, as an alternative to the traditional method of the grain sized stabilization, which is not adequate for this purpose. The mixtures produced with lateritics soils were evaluated after the compacting, they have not presented the broken grains. These mixtures performed very well with significant increase in the value of the resilience module, up to 288% above of the module of the aggregate. The results of the laboratory indicate that it is possible to use these residues in mixtures with laterític soil, for layers of low cost pavements.
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Sant'anna, Selenobaldo Alexinaldo Cabral de. "Indicadores de qualidade do solo em áreas de cana-de-açúcar dos Tabuleiros Costeiros de Alagoas." Universidade Federal de Sergipe, 2007. https://ri.ufs.br/handle/riufs/6639.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThe sugarcane crop is the major agricultural activity in the coastal tableland ecosystems in Alagoas State, exerting a remarkable influence in the economical and social aspects. This activity has been continuously and intensively conducted for several years and the necessity of environmental conservation and preservation of the several natural resources in this agroecosystem makes the adoption of sustainable practices mandatory for this activity. Among these resources, soil assumes a primary role and the evaluation of its quality through the observation and analysis of physical, chemical and biological indicators that are sensitive to management practices and robust to seasonal variations may be used to define this agroecosystem sustainability. Therefore, the objective of this work was to select indicator variables of soil conservation that fulfill the criteria of sensitivity to management and robustness to seasonal variability. For this, ten composite soil samples (0-10 cm) were taken from areas grown with organic sugarcane (OS), unburned sugarcane (US), and burned sugarcane (BS), as well as from an adjacent native forest (NF) used as a reference of the undisturbed condition. Sampling was carried out at two dates: July 2005 (rainy season) and March 2006 (dry season). The following variables were analyzed: microbial biomass-C (MBC), total organic C (TOC), soil enzyme activity by the fluorescein diacetate (FDA) hydrolysis technique, the weighed mean diameter of water stable soil aggregates (WSA), and the percent of macroaggregates (PMA). MBC and TOC were higher in NF than in the cultivated areas. No differences were observed in these C pools between the three sugarcane management treatments. The response of FDA to the crop management was dependent on the sampling time. In the rainy period, the activity followed the order: NF > OS > US > BS; in the dry season, only NF differed from the other treatments. Irrespective to the sampling time, WSA and PMA decreased according with the order NF > OS = US > BS. The variables WSA and PMA were quite sensitive to discriminate between sugarcane managements, and, at the same time, robust to seasonal variations. As an additional study, we analyzed the distribution of enzyme activity (fluorescein diacetate hydrolisys) across different diameter classes of water stable aggregates in soil samples from NF and US in order to verify the relationship between these variables. It was suggested the occurrence of two pools of fluorescein diacetate catalyzing enzymes in soils from NF and US. A non-monotonic relationship was observed between aggregate diameter and FDA. For both soils, intermediate aggregate size classes (0.25 to 1.00 mm) had lower FDA values than the classes bellow and above this diameter range.
No ecossistema dos tabuleiros costeiros do Estado de Alagoas a cultura da cana-deaçúcar destaca-se como a principal atividade agrícola exercendo influência nos aspectos econômico e ambiental da região. Esta atividade tem sido praticada de forma contínua e intensa ao longo do tempo e a necessidade de conservação ambiental e preservação dos diversos recursos presentes neste agroecossistema têm exigido que a sua utilização seja sustentável. Entre os recursos existentes, o solo assume papel importante e a avaliação da sua qualidade através da observação e análise dos indicadores físicos, químicos e biológicos do solo que sejam sensíveis às práticas de manejo e resistentes a variações sazonais podem ser utilizadas para definir a sustentabilidade deste agroecossistema. Assim o objetivo deste trabalho foi selecionar variáveis indicadoras de conservação do solo que atendam aos critérios de sensibilidade ao manejo e robustez as variações sazonais. Para tanto, dez amostras compostas de solo (0-10 cm) foram coletadas de áreas sob cana-orgânica (CO), cana-crua (CC), e cana-queimada (CQ), bem como de uma mata nativa (MN) adjacente usada como referência da condição não-manejada. A amostragem foi realizada em duas datas: julho de 2005 (chuva) e março de 2006 (seca). Avaliaram-se o C da biomassa microbiana (CBM), o C orgânico total (COT), a atividade enzimática do solo pela taxa de hidrólise do diacetato de fluoresceína (FDA), o diâmetro médio ponderado de agregados estáveis em água (DMA) e a percentagem de macroagregados (PMA). O CBM e COT foram mais elevados na MN que nas áreas cultivadas, não diferindo, no entanto entre os três sistemas de manejo da cana-deaçúcar. A resposta de FDA aos manejos foi dependente da época de amostragem. No período chuvoso, os valores desta variável seguiram a ordem: MN > CO > CC > CQ; na época seca, apenas MN diferiu dos demais tratamentos. Independentemente da data de coleta, DMA e PMA decresceram na ordem MN > CO = CC > CQ. As variáveis DMA e PMA apresentaram sensibilidade satisfatória para diferenciar manejos de cana-deaçúcar e robustez à data de coleta. Após estes estudos foi analisada a distribuição da atividade enzimática medida pela hidrólise de FDA nas diferentes classes de agregados estáveis em água em amostras de solos de MN e cultivo de cana crua CC. Buscou-se com esta análise, averiguar o grau de associação entre o estado de agregação do solo e a atividade enzimática. Foi evidenciada a existência de uma compartimentalização diferenciada dos reservatórios de enzimas catalisadoras da hidrólise do FDA entre CC e MN. Observou-se uma relação não-monotônica entre estas duas variáveis. Para ambos os solos, classes de agregados intermediárias (0,25 a 1,00 mm) apresentaram menores valores de FDA que as classes abaixo e acima desta faixa de diâmetros.
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Rosa, Jaqueline Dalla. "Dinâmica da formação de crostas superficiais em função de práticas de preparo do solo e chuva simulada." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-20092012-154056/.
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As crostas são o resultado da degradação da estrutura superficial dos solos, favorecem a erosão e a degradação ambiental dos solos. Este estudo avaloiu a dinâmica da formação de crostas superficiais e as consequencias sobre a porosidade, condutividade hidráulica (K), retenção de água, densidade (Ds) e a rugosidade de um Argissolo Vermelho amarelo conduzido com diferentes sistemas de preparo do solo e aplicação de lâminas de chuva simulada. Avaliou-se também, através de um experimento em laboratório, os processos envolvidos na quebra dos agregados, sob chuvas simuladas. O experimento foi conduzido, nos anos de 2009 e 2010. Em parcelas de 15 x 30 m foram conduzidos os diferentes preparos do solo: preparo convencional (PC), preparo reduzido (PR) e sem preparo (SP). Dentro das parcelas instalou-se micro-parcelas de 1m x 1m, onde foram aplicadas diferentes lâminas de chuva simulada (0, 27, 54 e 80 mm) com intensidade de 80 mm h-1. Foram realizadas coletas de dados de rugosidade, medidas de K, coleta de amostras indeformadas de solo para análise da porosidade e confecção de lâminas delgadas, e também anéis cilíndricos para curva de retenção de água (CRA) e Ds do solo. No experimento de laboratório, utilizou-se dois solos (siltoso e argiloso) e duas classe de agregados (1-3 e 3-5 mm). Os agregados foram submetidos a diferentes chuvas simuladas (28mmh-1 + EC forte; 28mmh-1 + EC fraca; 90mmh-1 + EC forte; 90mmh-1 + EC fraca) e após avaliou-se o diâmetro médio ponderado dos agregados (DMP). A dinâmica da formação de crostas ocorreu de maneira diferenciada em ambos os sistemas de preparo. Nos sistemas de PC e PR a maior redução da porosidade, pelo efeito da chuva aplicada, ocorreu na camada da crosta e no sistema SP na camada da subcrosta. A camada da crosta foi responsável pela redução da porosidade e K, e aumento da Ds nos sistemas PC e PR. As maiores umidades volumétricas observadas nas CRA ocorreram no sistema de PR e as menores no PC e não demonstraram evolução entre as chuvas aplicadas. A rugosidade superficial do solo variou em função dos sistemas de preparo realizados. Os sistemas conservacionistas (PR e SP) apresentaram maior rugosidade no primeiro ano, no segundo ano a maior rugosidade foi observada no sistema SP. O PC demonstrou nos dois anos estudados a mesma tendência, em função das chuvas aplicadas, inicialmente ocorreu um aumento na rugosidade até uma chuva máxima diminuindo em seguida. No experimento em laboratório, as maiores reduções no DMP ocorreram até a lâmina de 3 e 2 mm para o solo argiloso e siltoso, respectivamente. Nas quantidades iniciais de chuva (lâminas iniciais) a intensidade foi determinante na redução do DMP, com o aumento da quantidade de chuva a energia cinética (EC) passou a influenciar a redução do DMP. A intensidade de 28 mm h-1 promoveu as maiores reduções do DMP possivelmente pelo maior tempo de exposição dos agregados ao molhamento.The crusts are the result of degradation of the surface structure of the soil, favoring erosion and environmental degradation of soils. This study evaluated the dynamics of the develop surface crusts and its consequences on the porosity, hydraulic conductivity (K), water retention, bulk density (Ds) and the roughness of a Typic Hapludult conducted with different systems of tillage and application of sheets simulated rainfall. Was also evaluated through the an laboratory experiment, the processes involved in the breakdown of aggregates under simulated rainfall. The experiment was conducted in the years 2009 and 2010. In plots of 15 x 30 m were installed the soil tillage: conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). Inside of the plots was installed micro-plots of 1m x 1m, which were applied different sheets of simulated rainfall (0, 27, 54 and 80 mm) with intensity of 80 mm h-1. Roughness data, K measurements, sampling of undisturbed soil samples for porosity analysis and preparation of thin sections, and also cylindrical rings for water retention curve (SWRC) and Ds, were collected. In the laboratory experiment two soils (Silt Loam and Clay Loam) and two aggregate classes (1-3 and 3-5 mm) were used. The aggregates were submitted to different simulated rainfall (28mmh-1 + KE strong; 28mmh-1 + KE weak; 90mmh-1 + KE strong; 90mmh-1 + KE weak) and after the mean weight diameter (MWD) was evaluated. The dynamics of crust formation occurred differently in both tillage systems. In the CT and RT systems the major reduction of the porosity, by effect of the applied rainfall, occurred in the crust layer and in the NT system occurred in the subcrosta layer. Crust formation was responsible for reducing the porosity and K, and increasing Ds, in RT and CT systems. The higher volumetric moisture contents observed in CRA occurred in the PR system and the lowest in CT. The CRA did not show changes between the applied rainfall. The surface roughness of the soil varied in relation to the tillage systems. RT and NT systems showed a higher roughness in the first year during the second year a higher roughness was observed in the NT system. The CT in the two years studied showed the same trend of evolution according to of applied rainfall, initially there was an increase in roughness up to a maximum rain and then decrease. In the laboratory experiment, the largest DMP reductions occurred in the 3 and 2 mm rainfall for the Silt Loam and Clay Loam soils, respectively. In the initial amounts of rainfall, the intensity was determinant in the MWD reduction. With the increase in the amount of rainfall, the kinetic energy influences the MWD reduction. The intensity of 28 mm h-1 produced the greatest reductions in DMP, possibly due to the longer exposure of the aggregates to wetting.
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Seben, Junior Getulio de Freitas [UNESP]. "Resistência tênsil relacionada com atributos de um Latossolo sob sistema de semeadura direta." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/88305.
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A avaliação da estrutura do solo pode ser realizada por um conjunto de atributos específicos e suas inter-relações. Assim, os objetivos foram: i) quantificar a resistência tênsil de agregados (RT), friabilidade do solo (FR), e teor de carbono (C), diâmetro médio ponderado (DMP), índice de estabilidade de agregados (IEA) e a densidade do solo (DS) e verificar a influência dos demais atributos na RT e FR; ii) avaliar a influência do formato dos agregados na RT e FR. O delineamento foi em blocos casualizados, em faixas, com três repetições. Os tratamentos foram constituídos de três seqüências de culturas de verão (milho, soja e rotação soja/milho) e sete culturas de inverno (milho, girassol, nabo forrageiro, milheto, guandu, sorgo e crotalária). Em cada parcela foram coletados quatro blocos de solo com dimensões de 10x20x15 cm de altura, comprimento e largura, respectivamente; destes blocos selecionaram-se agregados com diâmetro entre 19,0 e 12,5 mm. Foram avaliados a influência do formato dos agregados na determinação da RT e FR e a influência das seqüências de culturas na RT, FR, teor de água e de C, IEA, DMP e DS. Os dados foram submetidos à análise de variância e as médias dos tratamentos comparadas pelo teste de Tukey. Realizou-se correlação de Pearson entre a RT e FR com os demais atributos. Foi constatado que os agregados com base plana proporcionaram uma menor variabilidade em comparação aos esféricos, conferindo maior acurácia a medida da RT e que as seqüências de culturas não influenciaram o teor de C e a FR, mas afetaram a RT, o IEA, o DMP e a DS. Também foi constatado que a RT correlacionou-se positivamente com o IEA, DMP e C
Soil structure can be evaluated by a set of specific attributes and their correlations. The objectives of this study were to: i) quantify aggregate tensile strength (TS), soil friability (SF), carbon content (C), mean pondered diameter (MPD), aggregate stability index (ASI) and bulk density (BD) as well as evaluate the effects of the other attributes on TS and SF; ii) determine the influence of aggregate shape on TS and SF. The experimental design was the completely randomized block arranged in strip plots with three replications. Treatments consisted of three sequences of summer crops (corn, soybean and the rotation soybean/corn) combined with seven winter crops (corn, sunflower, forage turnip, millet, pigeon pea, sorghum and sunnhemp). Four blocks of soil measuring 10x20x15 cm of height, length and width, respectively, were taken from each plot. Then, aggregates with diameters of 19.0 and 12.5 mm were taken from them. The effects of aggregate shape on TS and SF were evaluated. Also, the influence of the crop rotations on TS, SF, C content, ASI, MPD and BD was determined. The results were submitted to variance analysis (F test) and means were compared by the Tukey test (p < 0.10). Pearson linear test was applied to evaluate the correlation between TS/SF and the other soil attributes. Filed aggregates provide lower variability compared to the spherical ones, resulting in higher accuracy to measure TS. The crop rotations did not affect C content and SF, but positively influenced TS, ASI, MPD and BD. Also, TS showed positive correlation with ASI, MPD and C content
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Wick, Abbey Foster. "Soil aggregate and organic matter dynamics in reclaimed mineland soils." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1400961671&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Peche, Filho Afonso. "Variabilidade da agregação em amostras de solos agrícolas como indicador de qualidade : uma proposta metodológica /." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/154445.
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As questões ambientais que envolvem os efeitos do manejo e da degradação do solo necessitam de forma acelerada de pesquisa e muita extensão. Novos saberes e conhecimentos têm alcançado parte da comunidade acadêmica, mas ainda está aquém das necessidades para técnicos e leigos envolvidos em trazer soluções para problemas da ocupação, uso e degradação das terras. O manejo e recuperação ambiental de áreas degradadas são complexos e requerem diferentes tecnologias para o diagnóstico e avaliação. O uso de indicadores como diâmetro médio geométrico e distribuição percentual de agregado são parâmetros de uso consolidados, mas trazem limitações para questões complexas como o diagnostico do estado e condição de agregação do solo. A agregação do solo vem sendo estudada desde o inicio do século passado, mas são poucos os avanços conseguidos em popularizar a analise de agregação do solo agrícola como uma ferramenta laboratorial e prática. Além de que, falta conhecimento para popularizar a condição de agregação como informação de uso corrente. O uso de imagens obtidas e processadas em alta resolução permite sua aplicação em diferentes ramos da ciência, podendo ser aplicada nos estudos relacionados com o processo de agregação permitindo viabilizar o mais conhecimento ao processo. Este trabalho tem como objetivo desenvolver uma proposta metodológica para determinar a condição da qualidade de agregação, com base na tipificação de agregados e nos efeitos da variabilidade de composição em amostras de solo agrícola. Foram utilizados parâmetros relacionados com a forma, superfície e biogênese de agregados como indicadores de variabilidade da agregação do solo em duas amostras de latossolo vermelho de textura média, sendo que uma delas é referente a uma parcela de solo que recebeu um produto fertilizante/agregante Microgeo® e outra parcela sem ter recebido o produto. A obtenção dos agregados foi através do processo de peneiramento via seca utilizando cinco peneiras de diferentes calibres. A análise de agregados foi realizada em laboratório a partir de uma sub-amostra contendo 100 agregados oriundos de cada peneira específica, totalizando 500 agregados por amostras individuais de solo, perfazendo um total de 1000 agregados avaliados. A partir da obtenção de 1000 imagens fotográficas, com auxílio de um programa de processamento de imagens, obtêm-se um banco de dados referentes aos parâmetros morfométricos. Através do uso de tecnologia Fuzzy obteve-se um banco de dados numéricos referente à tipificação com base na análise visual da forma, superfície e biogênese dos agregados. Para cada conjunto de dados foi elaborado uma representação gráfica da variabilidade e seu respectivo quadro analítico descritivo. Com auxílio de medidas separatrizes do tipo quintis os dados foram classificados de acordo com a tipologia de ocorrência. Foram utilizados como parâmetros morfométricos o “diâmetro de Feret”, e como parâmetro de tipificação rugosidade de superfície e a “saída Fuzzy de tipificação” (os valores de integração com uso da tecnologia Fuzzy) o qual denominamos “Indicie Fuzzy de Tipificação”. Os resultados permitem afirmar que o trabalho atendeu os objetivos proposto de oferecer para sociedade uma “metodologia para qualificar a agregação em amostras de solos agrícolas”. Os resultados permitem aceitar as hipóteses formuladas e concluir que o estudo sobre efeitos da variabilidade permite quantificar, diagnosticar e qualificar o estado de agregação de amostras de solo.
Environmental issues involving the soil management effects and degradation are increasing and need to be extensively researched to be managed. New knowledge about solutions has been produced by academic research, but is still insufficient to solve the problems faced by technicians and other people involved to the field land use planning and degradation problems. Furthermore, the management of soil quality and land reclamation is complex, requiring different technologies for diagnosis and evaluation. The use of indicators, such as geometric mean diameter and percentage distribution of aggregate size, represents classical approaches, but both have limitations in treating the complexity of soil aggregation process. The soil aggregation has been studied since the beginning of the last century, but few advances have been made to popularize it to analyze agricultural soil quality. There are several difficulties to develop laboratory routines and practical tool to evaluate it. The use and processing of high resolution images have been widely applied in several fields of science and represents an interesting solution to study soil aggregation. To fill the existing gap, this works presents a methodological proposal to assess the quality of soil aggregation, by a classification of soil aggregates in terms of composition and variability. Agricultural soil aggregates were analyzed by three attributes: shape, surface and biogenesis. These parameters were used as indicators of soil aggregation quality, and the variability on each parameter was evaluates for two samples of medium texture red latosol, one of them referring to a plot of soil that received a fertilizer/aggregate product Microgeo® and another without receiving it. The aggregates were passed through the dry sieving process using five different sizes. The laboratorial analysis was performed by subsampling 100 aggregates from each sieve, totaling 500 aggregates per soil samples, and making a total of 1000 aggregates. Each soil aggregate was photographed, totalling1000 pictures, later processed on ImageJ. All results were organized in a database, containing information about the morphometric parameters of all soil aggregates. Fuzzy Logic was employed to transform the aggregate type into numeric values, using the visual analysis of the shape, surface and biogenesis. For each data set, a graphical representation of the variability and its descriptive statistics were calculated, producing an analytical framework. Statistical measures were used to classify the samples according to occurrence of aggregate type. To classify the samples and two sets of indexes were developed. The first one was based on the "Feret diameter", used as morphometric indicator, and the second one based on the "Fuzzy typing output", index produced by the integration of the values of shape, surface and biogenesis by a Fuzzy Inference System, which we call "Fuzzy index of typing". These results allowed affirming that the work fulfill the proposed objectives, offering to society a "methodology to qualify the aggregation quality in samples of agricultural soils". The results also allowed us to accept the formulated hypotheses and conclude that the study of variability can be used to quantify, diagnose and qualify the state of aggregation of soil samples.
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Aubertin, Marie-Liesse. "Biochar-compost mixtures : interactions and impact on carbon sequestration and soil fertility." Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS173.
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Dans le contexte actuel des enjeux environnementaux, des stratégies innovantes d’amendement organique peuvent être utilisées afin d’améliorer les propriétés agronomiques du sol, tout en augmentant la séquestration du carbone (C) dans le sol. La combinaison de biochar hautement stable avec du compost, matériau riche en nutriments et contenant du C labile, pourrait être une de ces stratégies, dans un contexte d’économie circulaire. L’objectif de la thèse était d’étudier l’existence d’interactions entre biochar et compost et le cas échéant, de déterminer les mécanismes responsables de leurs effets sur la dynamique du C et de l’azote, ainsi que sur les plantes, à différentes échelles de temps. Pour ce faire, nous avons réalisé des expériences au laboratoire et au champ et analysé les stabilités thermiques et biologiques. La stabilité thermique du biochar a été affectée par les interactions biochar-compost, survenant dès leur mélange. L’altération artificielle a induit des changements sur la stabilité biologique des deux composants. Dans les conditions au champ, les processus induits par les interactions biochar-compost n’ont pas impacté significativement la dynamique du C des mélanges, contrairement à leurs effets sur la friabilité du biochar et la dynamique de l’azote. En conclusion, les interactions entre biochar et compost peuvent se produire à différentes échelles de temps et affecter significativement les propriétés des matériaux ainsi que leur performance en tant qu’amendement organiqueIn the context of global challenge, innovative organic amendment strategies could be used to improve soil agronomic properties in addition to increasing carbon (C) sequestration in soil. The combination of highly stable biochar with compost, a nutrient-rich material containing labile C, may be a solution to improve C sequestration while enhancing soil fertility in the context of a circular economy. Aim of the thesis was to examine if there are biochar-compost interactions and if yes, what are the mechanisms determining their effect on C and nitrogen (N) dynamics and plant growth, at different time scales. To this end we used laboratory and field experiments and analyzed for biological and thermal stability. The thermal stability of biochar was affected by biocharcompost interactions, which may already occur during their blending. Artificial weathering influenced the biological stability of both materials. Under field conditions, these processes did not significantly influence the carbon dynamics of the mixture, while biochar friability and N dynamics were affected by biochar-compost interactions. We conclude that biochar and compost interactions may occur at different time scales and affect their material properties and performance as soil amendment
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Szakács, Gábor Gyula Julius. "Estoques de carbono e agregados do solo cultivado com cana-de-açucar: efeito da palhada e do clima no centro-sul do Brasil." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/64/64132/tde-16092008-103340/.
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O estudo foi dividido em quatro partes. Na primeira parte analisou-se o impacto do clima na estocagem de carbono em solos de canaviais sem a queima da palhada. Foram escolhidos três regimes climáticos contrastantes do centro-sul do Brasil. O potencial de seqüestro de carbono orgânica no solo (COS) foi determinado, em cada regime climático, de acordo com a taxa anual de carbono remanescente no solo proveniente da palhada depositada. Para obter esta taxa, compararam-se os estoques de COS em canaviais com e sem queima da palhada. Esse ganho anual foi comparado com a entrada anual de carbono via palhada depositada. O ganho anual de COS (0-30 cm) em canaviais sem queima da palhada não resultou em diferenças significativas por clima: 1, 97 Mg ha-1 (clima norte), 2,00 Mg ha-1 (clima centro) e 1,70 Mg ha-1 (clima sul). Os regimes climáticos estudados também não revelaram diferenças significativas entre suas temperaturas e precipitações médias anuais. Porém, o aumento anual de COS um pouco menor no clima sul levou à conclusão que o potencial de seqüestro de carbono diminui ligeiramente em latitudes mais altas, devido à maior precipitação no centro-sul do Brasil. Na segunda parte avaliou-se o impacto da palhada sobre a estabilidade de agregados dos solos, que foi calculada pelo método de fracionamento proposto por Six et al. (2000a). A estabilidade de agregados no solo do canavial sem a queima da palhada aumentou, em média, 15,3% por ano na profundidade 0-30 cm. Na terceira parte, avaliou-se a diferença da estabilidade de agregados entre canaviais e mata nativa. O solo da mata nativa mostrou uma estabilidade de agregados significativamente maior (7,2 vezes). Supõe-se que a estabilidade de agregados seja maior na mata nativa como resultado da maior presença de matéria orgânica e biota no solo. Na quarta parte avaliou-se a origem do carbono nos agregados estáveis em água de fluxo contínuo para determinar que forma de agregação possui a melhor proteção contra a decomposição de carbono. Houve uma diferença significativa de \'delta\'13C entre os macroagregados e microagregados na camada superior, com 10% mais \'delta\'13C nos macroagregados. Isto indica mais carbono derivado da cobertura vegetal atual (C4), ou seja, mais incorporação da palhada nos macroagregados. O \'delta\'13C da fração de partículas livres ou agregados não estáveis em água de fluxo contínuo é menor em todas as profundidades, indicando que a matéria orgânica recente (C4) encontra-se no solo principalmente de forma agregada estável em água, evidenciando seu papel fundamental na estabilidade dos agregados. Constatou-se também, que quanto mais novo o macroagregado, maior o seu teor em carbono. Nos microagregados verificou-se o efeito contrário. Quanto mais velho o microagregado, maior o seu teor em carbono. Isso indica que o microagregado possui uma melhor proteção contra a decomposição de carbono, e também a capacidade de um aumento no teor de carbono, no decorrer do tempo, em virtude da assimilação de carbono mais novo. Conclui-se, que em termos de seqüestro de carbono de longa duração, é propício avaliar mecanismos de proteção do carbono recalcitrante dentro dos microagregados e estudar como técnicas agrícolas podem proteger melhor esta fraçãoThe study was divided in four parts. The first part investigated climate impact on soil carbon stocks in sugar cane fields cultivated without green trash burning. For this purpose, three contrasting climates were chosen in Central and Southern Brazil. The sequestration potential of soil organic carbon (SOC) was determined for each climate, calculating how much of the carbon derived from deposited green trash remains in the soil every year. To obtain this rate, SOC stocks of sugar cane fields cultivated with and without green trash burning were compared. The annual difference (0-30 cm) did not differ significantly between climates: 1, 97 Mg ha-1 (Northern Climate), 2,00 Mg ha-1 (Central Climate) and 1,70 Mg ha-1 (Southern Climate). The climates did not show significant differences between their average annual temperatures and their annual precipitation. Nevertheless, a slightly smaller gain of SOC stocks in the Southern Climate leads to the conclusion that higher latitudes tend to stock slightly less COS due to higher annual precipitation. The second part evaluated the impact of green trash deposition on soil aggregate stability, which was calculated according to Six et al. (2000a). Soil aggregate stability under sugar cane fields cultivated with green trash burning had an average increase of 15,3% for soil depth 0-30 cm. The third part studied soil aggregate stability between sugar cane and natural forest vegetation. The forest soil revealed significantly higher (7,2 times) aggregate stability, supposedly due to higher organic matter content and more soil biota. The forth part examined the origin of carbon inside water-stable aggregates to determine which aggregation form provides better protection against carbon decomposition. The top soil layer showed a significant difference in \'delta\'13C between macro-aggregates (10% more \'delta\'13C) and microaggregates which means that more carbon derived from green trash (C4) was incorporated in macro-aggregates. \'delta\'13C of free soil particles or water-unstable aggregates is smaller for all soil layers indicating that fresh organic matter (green trash) is predominantly encountered in a water stable aggregated form in the soil. Furthermore, a correlation analysis revealed that more recent macro-aggregates had higher C content. The opposite was observed for micro-aggregates: the older the micro-aggregate, the higher its carbon content, leading to the conclusion that microaggregates protect carbon better against decomposition and are also capable to enrich their carbon pool through C assimilation. Given its long-term soil carbon sequestration potential, it is recommended to investigate carbon protection mechanisms for the recalcitrant C pool in micro-aggregates and also to study how agricultural techniques could improve the protection of the recalcitrant C pool
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Seben, Junior Getulio de Freitas. "Resistência tênsil relacionada com atributos de um Latossolo sob sistema de semeadura direta /." Jaboticabal : [s.n.], 2010. http://hdl.handle.net/11449/88305.
Full textAbstract:
Resumo: A avaliação da estrutura do solo pode ser realizada por um conjunto de atributos específicos e suas inter-relações. Assim, os objetivos foram: i) quantificar a resistência tênsil de agregados (RT), friabilidade do solo (FR), e teor de carbono (C), diâmetro médio ponderado (DMP), índice de estabilidade de agregados (IEA) e a densidade do solo (DS) e verificar a influência dos demais atributos na RT e FR; ii) avaliar a influência do formato dos agregados na RT e FR. O delineamento foi em blocos casualizados, em faixas, com três repetições. Os tratamentos foram constituídos de três seqüências de culturas de verão (milho, soja e rotação soja/milho) e sete culturas de inverno (milho, girassol, nabo forrageiro, milheto, guandu, sorgo e crotalária). Em cada parcela foram coletados quatro blocos de solo com dimensões de 10x20x15 cm de altura, comprimento e largura, respectivamente; destes blocos selecionaram-se agregados com diâmetro entre 19,0 e 12,5 mm. Foram avaliados a influência do formato dos agregados na determinação da RT e FR e a influência das seqüências de culturas na RT, FR, teor de água e de C, IEA, DMP e DS. Os dados foram submetidos à análise de variância e as médias dos tratamentos comparadas pelo teste de Tukey. Realizou-se correlação de Pearson entre a RT e FR com os demais atributos. Foi constatado que os agregados com base plana proporcionaram uma menor variabilidade em comparação aos esféricos, conferindo maior acurácia a medida da RT e que as seqüências de culturas não influenciaram o teor de C e a FR, mas afetaram a RT, o IEA, o DMP e a DS. Também foi constatado que a RT correlacionou-se positivamente com o IEA, DMP e CAbstract: Soil structure can be evaluated by a set of specific attributes and their correlations. The objectives of this study were to: i) quantify aggregate tensile strength (TS), soil friability (SF), carbon content (C), mean pondered diameter (MPD), aggregate stability index (ASI) and bulk density (BD) as well as evaluate the effects of the other attributes on TS and SF; ii) determine the influence of aggregate shape on TS and SF. The experimental design was the completely randomized block arranged in strip plots with three replications. Treatments consisted of three sequences of summer crops (corn, soybean and the rotation soybean/corn) combined with seven winter crops (corn, sunflower, forage turnip, millet, pigeon pea, sorghum and sunnhemp). Four blocks of soil measuring 10x20x15 cm of height, length and width, respectively, were taken from each plot. Then, aggregates with diameters of 19.0 and 12.5 mm were taken from them. The effects of aggregate shape on TS and SF were evaluated. Also, the influence of the crop rotations on TS, SF, C content, ASI, MPD and BD was determined. The results were submitted to variance analysis (F test) and means were compared by the Tukey test (p < 0.10). Pearson linear test was applied to evaluate the correlation between TS/SF and the other soil attributes. Filed aggregates provide lower variability compared to the spherical ones, resulting in higher accuracy to measure TS. The crop rotations did not affect C content and SF, but positively influenced TS, ASI, MPD and BD. Also, TS showed positive correlation with ASI, MPD and C content
Orientador: José Eduardo Corá
Coorientador: Carolina Fernandes
Banca: Marcílio Vieira Martins Filho
Banca: Zigomar Menezes de Souza
Mestre
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Mitsuiki, Cassio. "Efeito de sistemas de preparo de solo e do uso de microrganismos eficazes nas propriedades físicas do solo, produtividade e qualidade de batata." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/11/11136/tde-26022007-151401/.
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As propriedades físicas do solo são preponderantes para a qualidade e produtividade da cultura da batata. Assim, o objetivo do presente trabalho foi avaliar algumas propriedades físicas do solo e a produtividade e qualidade dos tubérculos de batata. O experimento foi instalado em áreas de produção de batata na Chapada Diamantina (BA), de abril a agosto de 2005. O solo foi preparado pelo sistema convencional e pelo sistema alternativo MAFES, ambos associados ou não com a aplicação de Microrganismos Eficazes (EM). Foram avaliadas: a densidade do solo, a estabilidade de agregados, a resistência do solo à penetração, a taxa de infiltração de água e a retenção de água no solo. Também foi avaliada a alteração dessas propriedades do solo em relação à área antes do preparo, que estava sob pastagem de Brachiaria brizantha. A massa de torrões e touceiras colhidas juntamente com os tubérculos, bem como os danos mecânicos verificados durante a colheita mecanizada e a porcentagem de tubérculos com danos causados por larva alfinete, sarna e podridões foram quantificados. A produtividade nos diferentes tratamentos foi avaliada dentro da classificação comercial. Em relação ao pasto, os preparos convencional e MAFES alteraram a maioria das propriedades físicas avaliadas. Na área preparada pelo sistema MAFES foi observado, em relação ao preparo convencional, menor resistência à penetração em profundidades de 20 a 45 cm e entre os camalhões. A taxa de infiltração de água foi semelhante entre as áreas preparadas pelos dois sistemas, porém no sistema convencional a infiltração é mais superficial ocorrendo de forma lateral ao longo do perfil. No sistema MAFES a infiltração ocorreu verticalmente no perfil do solo. Menor porcentagem de tubérculos com danos mecânicos foi obtida na área preparada pelo sistema MAFES, devido, principalmente, a menor massa de torrões e touceiras colhidas juntamente com os tubérculos nessa área. A aplicação de EM teve pouca influência nas propriedades físicas do solo, mas propiciou condições que favoreceram o ataque de larva alfinete e sarna aos tubérculos. Apesar da utilização de EM ter reduzido a produção de tubérculos na área preparada pelo sistema MAFES, a produtividade e qualidade dos tubérculos nessa área foi superior a da área preparada pelo sistema convencional.The physical soil properties have a relevant role on the yield and quality of potato crop. Thus, the purpose of the present research was to evaluate the effects on some soil physical properties on productivity and quality of potato tubers. The trial was set up in a commercial potato production field located in the Chapada Diamantina, BA, from April to August, 2000. Two distinct soil preparation systems (conventional and MAFES system), either associated or not with application of EM, have been trialed. The following soil properties were evaluated: bulk density, aggregate stability, soil penetration resistance, soil water retention and water infiltration rate. In addition, were evaluated the changes of such soil properties in comparison with the area cultivated with the grass Brachiaria brizantha, prior soil preparation. Other evaluations were performed such as the clod mass and clump of roots harvested together with potato tubers, the level of damage to the tubers caused by mechanical harvesting, and the amount of tubers affected by potato tuber moth, rots, and common scab. The yields of the different treatments were evaluated and tubers graded according to commercial patterns. Compared to the grass, both conventional and MAFES soil preparation systems have changed the physical soil properties studied. MAFES system outperformed the conventional preparation giving lesser resistance to penetration at 20 to 45 cm deep and between hills. The water infiltration rate was similar for both soil preparation systems; however for the conventional system the infiltration pattern is superficial occurring laterally in the soil profile. Regarding MAFES systems, the infiltration occurred vertically. The area prepared MAFES system also gave a fewer percentage of tubers exhibiting mechanical damage, due to smaller clod mass and clump of roots harvested together with potato tubers. EM application did not benefit physical soil properties, however influenced a higher attack of potato tuber moth and common scab. Although the yield decrease in the area prepared with MAFES system when the EM was applied, in this area the productivity and tuber quality outperformed the conventional system.
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Ayquipa, Espinoza Lorena Estefanny, and Benavente Branixa Nataly Vilca. "Propuesta de diseño de un pavimento rígido conformado de agregados marginales con presencia de cenizas volcánicas para el proyecto: Mejoramiento de carretera Moquegua – Omate - Arequipa, Tramo II, sector 1." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/652387.
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En el Perú existen zonas afectadas por la geología volcánica ya que disponen de insumos naturales llamados cenizas volcánicas. Este es un material formado por pequeños fragmentos de lavas silíceas de granos finos de colores blanquecinos, blandos y deleznables. Suelen presentar diversos grados de cementación, de tipo fisil, lo que los identifica en la categoría de suelos colapsables. Es por ello, que para la construcción del pavimento se requiere realizar la estabilización o mejoramiento de la subrasante para el siguiente proyecto que se desarrolla entre Arequipa y Moquegua.
La presente investigación tiene como objetivo evaluar el uso de agregados marginales con cenizas volcánicas para el diseño de losa de concreto hidráulico referida, la misma que como estructura será evaluada con los resultados del módulo de flexión y esfuerzo crítico.
Los resultados demostraron que, en la caracterización de agregados finos al contener cenizas volcánicas, no cumplan con todos los requerimientos propuestos en la norma peruana (EG-2013) del manual de carreteras. Sin embargo, el American Concrete Institute (ACI) incorpora excepciones para condiciones particulares de los áridos, posibilitando su uso a partir del cumplimiento de la resistencia y durabilidad requerida.
Se propuso realizar el diseño de una mezcla de concreto para una resistencia teórica de f´c= 280 kg/cm2. Sin embargo, al ensayar las probetas a los 28 días de curado se obtuvo una resistencia de f´c= 380 kg/cm2 esto se debe a la estrecha relación positiva que presenta la ceniza volcánica con el cemento puzolánico empleado para la mezcla.In Peru there are areas affected by volcanic geology and that have natural inputs called volcanic ash. This is a material formed by small fragments of siliceous lavas of fine grains of whitish, soft and delectable colors. They usually present varying degrees of cementation, of the fisile type, which identifies them in the category of collapsible soils. That is why, for the construction of the pavement it is necessary to perform the stabilization or improvement of the subgrade for the next project that is developed between Arequipa and Moquegua. The purpose of this research is to evaluate the use of marginal aggregates with volcanic ash for the design of the loss of referred hydraulic concrete, which will be determined as a structure with the results of the flexural and critical stress module. The results showed that, in the characterization of fine aggregates containing volcanic ash, they do not require all the requirements proposed in the Peruvian standard (EG-2013) of the road manual. However, the American Concrete Institute (ACI) incorporates the specific conditions of the aggregates, which allows its use based on compliance with the required strength and durability. It was proposed to design a concrete mix for a theoretical strength of f´c = 280 kg / cm2. However, when testing the probes after 28 days of curing, a resistance of f'c = 380 kg / cm2 was obtained, due to the close positive relationship between volcanic ash and the pozzolanic cement used for the mixture.
Tesis
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Larišová, Lucie. "Vliv vodní eroze na vybrané fyzikální vlastnosti půdy." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-392276.
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The aim of the dissertation thesis is the assessment of the degradation of selected soil properties due to water erosion, including the temporal dynamics of these properties and the assessment of how this change affects the cumulative infiltration of the soil in watershed. Between 2012 and 2015, undisturbed and disturbed soil samples were collected on three experimental areas and the cumulative infiltration of the soil was measured. Experimental areas were selected on sloping, erosion-endangered blocks of arable land, in three cadastral territories of the Czech Republic, and this in the cadastral areas of Větřkovice, Čejkovice and Hustopeče. The cumulative infiltration was measured in three landscapes positions of the slope and soil samples were collected in three landscapes positions of the slope, at soil crust, topsoil and subsoil. In the Pedological Laboratory at the Institute of Landscape Water Management, Brno University of Technology, the particle density, bulk density, porosity, soil texture and water stable aggregates were determined from the samples taken. The cumulative infiltration of the soil was measured using the Double Ring Infiltrometer, the Mini Disc Infiltrometer and the mobile rainfall simulator. Using one-way analysis of variance to analyze the differences among soil samples and infiltration test. In addition, the dependence of soil crust formation, its physical properties and its influence on the cumulative infiltration of the soil were monitored on the areas.
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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.
Full textAbstract:
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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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.
Full textAbstract:
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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Santos, Rosilene dos. "Propriedades de retenção e condução de água em solos sob condições de campo e em forma de agregados, submetidos aos plantios convencional e direto." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2008. http://tede2.uepg.br/jspui/handle/prefix/861.
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Previous issue date: 2008-01-20Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
It has been unquestionable the importance of the studies and researches that seek for the understanding of the physical and hydraulic properties of the soil and that these studies and researches try to correlate them with the soil physical attributes. This work presents the use of the methodology presented in Leeds-Harrison et al. (1994), developed for the determination of the saturated hydraulic conductivity at the level of aggregates of the soil and the use of Permeâmetro of Guelph for measures of that property in field.. In this work the aggregates of the soil were investigated submitted to systems conventional tillage and direct tillage. To correlate the hydraulic conductivity of the soil with its retention properties, the retention curves and distribution of pores of the aggregate near the saturation condition they were done through a system based on the idea of a funnel of porous plate or funnel of Haines. Measures of the bulk density, total porosity, macroporosity and microporosity of the investigated aggregates were also accomplished. The obtained results showed that the conventional tillage presented larger value of the saturated hydraulic conductivity on average compared with the direct tillage, so much in field conditions as in the form of aggregates. The direct tillage presented a capacity of larger retention compared to the conventional tillage. This can be due to the largest amount of microporous found in this tillage type. The pores distribution curves shows on average a larger amount of smaller pores in the aggregates of the direct tillage, what might have determined its smallest value of hydraulic conductivity in relation to the conventional tillage. The tillage type can propitiate the formation of pores with larger diameters, in which, firstly, allow larger values of saturated hydraulic conductivity. However, due to the no structures imposed to the soil samples, nothing can be affirmed in regard to the continuity of these types of pores.
É indiscutível a importância de estudos e pesquisas que visam o entendimento das propriedades físicas e hídricas do solo e de que tentem correlacioná-las com seus atributos físicos. Este trabalho apresenta a utilização da metodologia apresentada em Leeds-Harrison & Youngs (1997), desenvolvida para a determinação da condutividade hidráulica saturada ao nível de agregados de solo e o uso do Permeâmetro de Guelph para medidas dessa propriedade em campo. Nesta pesquisa foram investigados agregados de solo submetidos aos sistemas de plantio convencional e direto. Para correlacionar a condutividade hidráulica do solo com suas propriedades de retenção, as curvas de retenção e de distribuição de poros dos agregados próximos à condição de saturação foram feita através de um sistema baseado na idéia de um funil de placa porosa ou funil de Haines. Também foram realizadas medidas da densidade global, porosidade total, macroporosidade e microporosidade dos agregados investigados. Os resultados obtidos mostraram que o plantio convencional apresentou em média maior valor da condutividade hidráulica saturada comparada com o plantio direto, tanto em condições de campo como na forma de agregados. O plantio direto apresentou uma capacidade de retenção maior comparada com o plantio convencional. Isto pode ser devido ao maior número de microporos encontrados neste tipo de plantio. As curvas de distribuição de poros mostram em média um número maior de poros menores nos agregados do plantio direto, o que pode ter determinado seu menor valor de condutividade hidráulica em relação ao plantio convencional. O tipo de manejo pode propiciar a formação de poros com diâmetros maiores, os quais, em princípio, permitem maiores valores de condutividade hidráulica saturada. No entanto, devido às desestruturações impostas às amostras de solo, nada se pode afirmar a respeito da continuidade desses tipos de poros.
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Briedis, Clever. "Compartimentos da matéria orgânica do solo, agregação, mecanismos de proteção e sequestro de carbono influenciados pela calagem superficial em sistema plantio direto." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2010. http://tede2.uepg.br/jspui/handle/prefix/2202.
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Previous issue date: 2010-06-14Liming is the most often practice used to neutralize soil acidity, and also promotes chemical changes that can alter the soil organic matter (SOM) pools and the mechanisms of flocculation, formation and stabilization of macro-and microaggregates. The objective of this study was to evaluate carbon sequestration, in the whole and in the aggregates samples, and the changes in the SOM pools affected by liming in a long-term no-tillage. The experiment was conducted in an Oxisol, located in Ponta Grossa, PR. The experimental design was a randomized complete block, arranged as split plot with three replications. The main plot consisted of dolomite lime applied on the soil surface at a 0 or 6 Mg ha-1 in 1993, and 0 or 3 Mg ha-1 in 2000 in plots previously with and without lime, and the treatments was assigned as: 0+0, 6+0, 0+3 and 6+3 Mg ha-1. The subplots were represented by sampling depth and consist of 0-2.5, 2.5-5, 5-10 and 10-20 cm layer. The soil samples were taken in September 2008 and the total organic carbon (TOC) was analyzed in the whole sample, in the aggregates and in the particulate organic carbon (POC) and in the fraction associated with minerals carbon (OCAM). Aggregates of 8-19 mm, in the 0-2.5 cm layer were analyzed by using scan microscope spectrometer X-ray (EDS) for elemental analysis of carbon (C) and calcium (Ca). Liming promoted accumulation of TOC mainly in the layer 0-2.5 cm. The TOC stocks at 0-20 cm were 49.9, 52.9, 52.7 and 57.5 Mg ha-1 for 0+0, 6+0, 0+3, 6 +3 treatments, respectively. Stocks in the SOM fractions were also increased with liming. The increase in POC stock was close relationship (R2 = 0.98, P = 0.011) with the C accumulated input through crop residue, which was higher in plots that were limed. A positive correlation was found between TOC and C extracted in hot water (CHW), total polysaccharides (TP) and labile (LP). Correlations also showed that TOC had a closer relationship with POC than with OCAM, suggesting a greater influence on the labile fraction of TOC increase with liming. In aggregate, the effect of liming in TOC accumulation was mainly in 0-2.5 cm depth. The treatments with liming showed high mean weight diameter (MWD), which provided a large stock of TOC in the 8-19 mm aggregate size. A higest proportion of large aggregates with liming was closely correlated with the TOC content of whole sample. The highest liming dosis resulted in both COP and in OCAM, in the largest class of aggregates. The proportion of POC average of the treatments in relation to OCAM, this class of aggregates, has decreased in depth, and were 18, 13, 10 and 8% at depths of 0-2.5, 2.5-5, 50-10 and 10-20, respectively. Elemental analysis of C and Ca showed a positive correlation of those elements contained in a section of clay from the center of 8-19 mm aggregates. The results suggest that application of lime in soil with clay fraction dominated by kaolinite, brings benefits to structuring and promotes an increase of C in the whole sample and in aggregates.
A calagem é a prática mais utilizada para neutralizar a acidez do solo, porém promove também modificações químicas capazes de alterar os compartimentos da matéria orgânica do solo (MOS) e mecanismos de floculação, formação e estabilização de macro e microagregados. O objetivo desse trabalho foi avaliar o seqüestro de carbono, na amostra integral e nos agregados, e as alterações nos compartimentos da MOS afetados por calagem superficial em sistema plantio direto de longa duração. O experimento foi conduzido em um Latossolo Vermelho textura média, no município de Ponta Grossa, PR. O delineamento experimental foi o de blocos completos ao acaso em parcelas subdivididas, com três repetições. As parcelas consistiram da aplicação de calcário dolomítico na superfície do solo na dose de 0 ou 6 Mg ha-1 em 1993, e dose de 0 ou 3 Mg ha-1 em 2000 nas parcelas previamente com e sem calcário, compondo os tratamentos: 0+0; 6+0; 0+3 e 6+3 Mg ha-1. As subparcelas foram constituídas pelas profundidades de coleta, sendo realizadas em 0-2,5, 2,5-5, 5-10 e 10-20 cm de profundidade. As coletas de solo foram realizadas em setembro de 2008 e analisados os conteúdos de carbono orgânico total (COT) na amostra total, nos agregados e nas frações particulada (COP) e associada aos minerais (COAM) da matéria orgânica do solo (MOS). Agregados de 8-19 mm, da camada 0-2,5 cm, foram analisados através do uso de espectrômetro de dispersão de raios X (EDS) para a análise elementar de carbono (C) e cálcio (Ca). A calagem promoveu acúmulo de COT, principalmente na camada 0-2,5 cm. Os estoques de COT na camada de 0-20 cm foram 49,9, 52,9, 52,7 e 57,5 Mg ha-1 para os tratamentos 0+0, 6+0, 0+3 e 6+3, respectivamente. Os estoques nas frações da MOS também foram aumentados com a calagem. O aumento no estoque de COP foi estreitamente relacionado (R2=0,98; P=0,011) com a adição acumulada de C via resíduo cultural, a qual foi mais elevada nas parcelas que receberam calagem. Houve correlação positiva entre COT e carbono em água quente (CAQ), polissacarídeos totais (PT) e lábeis (PL). Correlações também demonstraram que o COT teve relação mais estreita com o COP do que com COAM, sugerindo maior influência da fração lábil no aumento de COT com a calagem. Nos agregados, a calagem proporcionou acúmulo de COT principalmente na profundidade de 0-2,5 cm. A calagem aumentou o diâmetro médio ponderado (DMP), proporcionando grande estoque de COT na classe de agregado 8-19 mm. A elevada proporção de agregados grandes nos tratamentos com calagem foi estreitamente correlacionado com o conteúdo de COT da amostra integral. A maior dose de calcário proporcionou aumento no estoque de COT tanto em COP quanto em COAM, visto principalmente na maior classe de agregados. A proporção de COP em relação ao COAM, na média dos tratamentos, nessa classe de agregados, diminuiu em profundidade, ficando em torno de 18, 13, 10 e 8 % nas profundidades de 0-2,5, 2,5-5, 5-10 e 10-20, respectivamente. Análise elementar de C e Ca demonstraram correlação positiva dos dois elementos contidos em uma secção da fração argila do centro de agregados de 8-19 mm. A aplicação de calcário, em solo dominado na fração argila por caulinita, traz benefícios à estruturação e promove aumento de C na amostra integral e nos agregados.
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Aquino, Deodato do Nascimento. "Cycling carbon and spectrum characterization at thinned and native tropical dry forest - Caatinga." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16051.
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nÃo hÃThe aim of this study was to evaluate the effects in the Caatinga biome of the technique of thinning on the dynamics of herbaceous phytomass productivity; fine roots; the deposition, accumulation and rates of decomposition of litter; aggregate stability; respirometry of the soil; stocks of carbon and nitrogen; and characterisation of changes in the spectral behaviour of the canopy. The study was carried out in two stages: the first in watersheds in the town of Iguatu, in the south central region of the State of CearÃ, Brazil, and the second in the watershed of the Caxitorà River, in the northern region of the state. The Iguatu experimental area comprised two watersheds, one under thinning for 5 years (CR5) and the other preserved with natural vegetation for 35 years (CS35). The variables to be sampled were: productivity of herbaceous biomass; fine roots; gravimetric moisture; isotope δ13C (â); aggregate stability; deposition, accumulation and rates of decomposition of litter; and stocks of total organic carbon and total nitrogen in the 0-20, 20-40 and 40-60 cm layers, from April 2013 to March 2014. The data were submitted to the analysis of means test and compared by t-test (p≤ 0.05). The increase in the intensity of herbaceous plants resulting from thinning contributed to an increase in stocks of total organic carbon (249% and 139% in the 20-40 cm and 40-60 cm layers respectively) and of total nitrogen (142% and 137% respectively), in relation to the area under preservation. The 0-10 cm layer of CR5 stored double the amount of fine roots found in CS35. In the topsoil (0-20 cm) of CR5, aggregates with a size 2.15 times greater than those found in CS35 were obtained. The greater conservation of litter on the soil of CR5 is associated with the greater input of lignified woody biomass from thinning, and consequently with the lower rates of decomposition and respirometry, which are evidenced by the low CO2 emissions into the atmosphere. Thinning in a Vertisol of the Caatinga biome has an influence on soil structure and on the stocks of carbon and nitrogen, making possible lower rates of CO2 emission and improving conditions for the infiltration of water. In the second phase of the experiment, SRTM (Shuttle Radar Topography Mission) data were used to evaluate the effect of the illumination geometry on the spectral characterisation of the canopy, as well as images from the OLI/Landsat 8 sensor, representative of the rainy and dry seasons of 2013. The images were converted into physical values (surface reflectance factors), the NDVI was calculated, and with the technique of principal component analysis images PC1 and PC2 were generated. Dispersion for the values of PC1 and PC2 from the different canopies was evaluated in a two-dimensional space. It was found that the reflectance intensity of the incident electromagnetic radiation in canopies of the caatinga biome is not only influenced by seasonality, but also by the illumination geometry arising from the topographical characteristics of the terrain. The effect of shading was predominant during the dry season, especially under low lighting conditions, irrespective of the structure of the plant cover. The NDVI proved to be unsuitable for detecting changes in the spectral behaviour of the Caatinga biome during the rainy season.
Objetivou-se com este trabalho avaliar os efeitos da tÃcnica de raleamento do bioma caatinga sobre a dinÃmica da produtividade de fitomassa herbÃcea; raÃzes finas; deposiÃÃo, acumulaÃÃo e taxas de decomposiÃÃo da serapilheira; estabilidade de agregados; respirometria do solo; estoque de carbono, nitrogÃnio e caracterizaÃÃo das alteraÃÃes no comportamento espectral do dossel. O estudo foi conduzido em duas etapas: a primeira em microbacias hidrogrÃficas no municÃpio de Iguatu, regiÃo centro sul e a segunda na bacia hidrogrÃfica do rio CaxitorÃ, regiÃo norte, ambas no estado do CearÃ. A Ãrea experimental de Iguatu consistiu de duas microbacias adjacentes, sendo uma raleada por 5 anos (CR5) e a outra conservada com vegetaÃÃo natural hà 35 anos (CS35). As variÃveis amostradas foram: produtividade de fitomassa herbÃcea, raÃzes finas, umidade gravimÃtrica, isÃtopo δ13C (â), estabilidade de agregados, deposiÃÃo, acumulaÃÃo e taxas de decomposiÃÃo da serapilheira, estoque de carbono orgÃnico total e nitrogÃnio total nas camadas de 0-20, 20-40 e 40-60 cm entre abril/2013 e marÃo/2014. Os dados foram submetidos à anÃlise de teste de mÃdia e confrontados pelo Teste T (p≤0,05). O aumento da intensidade de plantas herbÃceas decorrente da tÃcnica de raleamento contribuiu para o acrÃscimo nos estoques de carbono orgÃnico total (249% e 139% nas camadas 20-40 cm e 40-60 cm, respectivamente) e do nitrogÃnio total (142% e 137%, respectivamente) em relaÃÃo à Ãrea conservada. A camada de 0-10 cm da parcela CR5 armazenou o dobro do quantitativo de raÃzes finas encontradas em relaÃÃo a CS35. Na camada superficial do solo (0-20 cm) da CR5 foram obtidos agregados com tamanho de 2,15 vezes acima dos obtidos na CS35. A maior conservaÃÃo de serapilheira no solo da CR5 està associada aos maiores aportes de fitomassa lenhosa lignificada proveniente do raleamento, e consequentemente das menores taxas de decomposiÃÃo e respirometria, constatada pelas baixas emissÃes de CO2 à atmosfera. O raleamento em Vertissolo do bioma Caatinga exerce influÃncia na estruturaÃÃo do solo, no estoque de Carbono e NitrogÃnio, possibilitando as menores taxas de emissÃo de CO2 e melhorando as condiÃÃes para a infiltraÃÃo de Ãgua. Jà na segunda etapa do experimento, foram utilizados dados do SRTM (Shuttle Radar Topography Mission) para avaliaÃÃo do efeito da geometria de iluminaÃÃo na caracterizaÃÃo espectral do dossel, alÃm de imagens do sensor OLI/LANDSAT 8 representativas da estaÃÃo chuvosa e seca de 2013. As imagens foram convertidas em valores fÃsicos (fatores de reflectÃncia de superfÃcie), calculado o Ãndice NDVI e, a partir da tÃcnica de componentes principais, geradas imagens PC1 e PC2. Foram avaliadas as dispersÃes dos valores de PC1 e PC2, em um espaÃo bidimensional, provenientes dos diferentes dossÃis. Os resultados indicaram que a intensidade de reflectÃncia da radiaÃÃo eletromagnÃtica incidente em dossÃis do bioma caatinga à influenciada tanto pela sazonalidade climÃtica quanto pela geometria de iluminaÃÃo decorrentes das caracterÃsticas topogrÃficas do relevo. O efeito sombreamento foi predominante durante o perÃodo seco, principalmente para condiÃÃo de pouca iluminaÃÃo independentemente da estrutura de cobertura vegetal. O NDVI nÃo se mostrou adequado para detectar alteraÃÃes no comportamento espectral do bioma caatinga durante a estaÃÃo chuvosa.
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Pelá, Adilson [UNESP]. "Efeito de adubos orgânicos provenientes de dejetos de bovinos confinados nos atributos físicos e químicos do solo e na produtividade do milho." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/99979.
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pela_a_dr_botfca.pdf: 679169 bytes, checksum: 8915ce777c2e9e3c2e6eda225c7033fa (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O presente trabalho teve como objetivo avaliar o efeito da utilização de adubos orgânicos, produzidos por diferentes processos de reciclagem de dejetos bovinos criados em sistema de confinamento para novilhos superprecoces, nos atributos químicos e físicos de um LATOSSOLO VERMELHO Distrófico e na produtividade da cultura do milho. O experimento foi conduzido por duas safras agrícolas, 2002/2003 e 2003/2004. Utilizou-se o delineamento experimental em blocos casualizados com quatro repetições e seis tratamentos: T1 = efluente de biodigestor; T2 = esterco de esterqueira; T3 = composto orgânico; T4 = vermicomposto; T5 = adubo mineral; T6 = testemunha (sem utilização de adubos). As parcelas possuíam 15 m de comprimento por 8 m de largura, com área total de 120 m2. As quantidades para cada fonte orgânica foram calculadas com base nos seus teores de nitrogênio, para aplicação de 120 kg ha-1 de N. No tratamento T5 utilizou-se uma formulação N-P2O5-K2O, com base na análise do solo para P e K, e também 120 kg ha-1 de N, dos quais 30 kg foram aplicados na base e o restante em cobertura, em uma única aplicação, aos 33 e 37 dias após a emergência das plantas, na primeira e segunda safra, respectivamente. Os adubos orgânicos foram incorporados ao solo por meio de uma gradagem, antes da semeadura. O milho, cv. híbrido DKB 350 foi semeado dia 6 de janeiro de 2003 na primeira safra, e no dia 26 de dezembro de 2003 na segunda safra, com espaçamento de 90 cm entre linhas, e população de 55000 plantas por hectare. Os atributos do solo foram avaliados nas camadas de 0-0,10 e 0,10-0,20 e 0,20-0,30 m. Os atributos físicos avaliados foram o diâmetro médio ponderado, a argila dispersa em água, a resistência à penetração, a condutividade hidráulica saturada, a densidade do solo, porosidade total, macro e microporosidade...
The present work had as its aim to evaluate the effect of cattle manure usage, produced by different processes of bovine dejections recycling raised in pen system for superprecocious steers in the chemical and physical properties of a distrophyc Red Oxisol and in the maize productivity. The experiment was carried out by two crop harvests 2002/2003 and 2003/2004. A completely randomized block design was used with four replications and six treatments: T1 = biodigestor effluent; T2 = cattle manure; T3 = organic composition; T4 = vermicompost; T5 = mineral fertilizer; T6 = witness (without fertilizer application). The parcels were 15 meters long and 8 meters wide, with a total area of 120 square meters. The amounts for each organic source had been calculated based on their nitrogen concentration, for a N application of 120 kg ha-1. In T5 treatment, a N-P2-O5-K2O formula was used, based on the soil analysis for P and K, and also 120 kg ha-1 of N, of which 30 kg were applied in the base and the rest in the covering, in a single application, at 33 and 37 days after the plant emerging, in the first and second harvests, respectively. The organic matter had been incorporated to the soil by grading, before sowing. The maize, cv. Hybrid DKB 350 was sown in January 6th, 2003 in the first harvest and in December 26th, 2003 in the second harvest, with a distance of 90 cm between the lines and a population of 55,000 plants per linear meter. The soil attributes were evaluated in the 0-0,10 and 0,10-0,20 and 0,20-0,30 layers. The evaluated physical attributes were the mean weighed diameter, the water dispersed clay, the penetration resistance, the saturated hydraulic conductivity, the soil bulk density, total porosity, macro and microporosity. Concerning the chemical attributes, the fractioned organic matter, macro and micronutrients, pH... (Complete abstract, click eletronic address below)
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Geeves, Guy William, and not available. "Aggregate Breakdown and Soil Surface Sealing under Rainfall." The Australian National University, 1997. http://thesis.anu.edu.au./public/adt-ANU20010702.142014.
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Aggregate breakdown is an important process controlling the availability of fine soil material necessary for structural sealing of soil surfaces under rainfall. It may be caused by slaking resulting from rapid soil wetting and by physical dispersion resulting from direct and indirect energetic raindrop impacts. Relationships have been proposed by others predicting steady infiltration rate and saturated hydraulic conductivity from final aggregate size following high energy rainfall on initially dry, uncovered soil surfaces. Under these extreme conditions, both rapid wetting and energetic raindrop impact result in maximum aggregate breakdown and surface sealing. Knowledge of the relative importance of these two agents under less severe conditions and knowledge of how increased aggregate stability due to conservative soil management may ameliorate them should improve prediction and management of aggregate breakdown and surface sealing.
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This study has isolated and quantified effects of rapid soil wetting and energetic raindrop impact on aggregate breakdown and surface sealing. Simulated rainfall was applied to re-packed soils from differing tillage treatments on light textured soils from near Cowra and Condobolin in New South Wales, Australia. Aggregate breakdown was assessed using aggregate size distribution, determined by wet sieving and summarised by a range of statistics. The degree of breakdown was assessed after 66 mm of simulated rainfall whilst the rate of change in aggregate size distribution was assessed by sampling after 5, 10, 15, 30 and 60 mm. The degree of surface sealing was assessed using final surface hydraulic conductivity after 66 mm rainfall calculated from inferred infiltration and measured sub-seal soil water potential. The rate of surface sealing was assessed prior to ponding using cumulative rainfall volume at ponding and throughout the post-ponding phase by decline in surface hydraulic conductivity as a function of cumulative rainfall kinetic energy. Two levels of raindrop kinetic energy flux and three wetting treatments were used to isolate effects of these agents of aggregate breakdown and surface sealing.
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Significant surface aggregate breakdown was observed when either rapid soil wetting or highly energetic raindrop impact were allowed to occur. The majority of the data suggest a negative interaction between the two agents. When soil was initially dry rapid soil wetting was the dominant agent causing rapid aggregate breakdown, generally within the first 5 mm of rainfall. When rapid soil wetting was prevented by tension pre-wetting, energetic raindrop impact was the dominant agent and was able to cause aggregate breakdown of an almost equivalent degree. This breakdown occurred over a period lasting for up to 30 mm of rainfall. In contrast, the rate and degree of surface sealing were influenced primarily by raindrop kinetic energy with highly energetic impact leading to significant surface sealing, irrespective of soil wetting. For the soils studied, it was concluded that structural sealing of surface soil, could be significantly reduced by protecting the soil surface from energetic raindrop impact but that prevention of surface aggregate breakdown required amelioration of both processes.
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In addition to the negative interaction referred to above, a positive interaction was observed whereby energetic raindrop impact occurring concurrently with rapid soil wetting caused a greater degree of aggregate breakdown and a greater degree of surface sealing than energetic raindrop impact occurring subsequent to rapid soil wetting. The effect on surface sealing may be explained by the effect of lower sub-seal water potential that necessarily results from initially dry soil condition required for concurrent rapid wetting. However, the effect on aggregate breakdown remains unexplained.
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Notwithstanding the above, permeability was reduced under high kinetic energy rainfall even when soil wetting was reduced to very slow rates by tension pre-wetting. Likewise, surface sealing did occur under low kinetic energy rainfall for the least stable soil following rapid soil wetting. It was concluded that threshold soil wetting rates and threshold rainfall energy levels, proposed by others, are either not applicable to these soils or are negligible.
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The rate and degree of aggregate breakdown was also dependent on the soil with the Cowra soil being more stable than the Condobolin soil. Greater aggregate stability brought about by conservative tillage treatments at both soil locations retarded and reduced surface sealing. Unvalidated simulation modelling was used to illustrate possible effects for the soil water balance. In contrast to the conclusions of Loch (1994b), that were based on soils throughout eastern Queensland, the soil water balance simulations predicted that the residual benefits in ameliorating surface sealing resulting from improved aggregate stability could significantly reduce point runoff under the lower intensity winter rainfalls experienced in southern New South Wales.
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Limited testing with Condobolin soil following tension pre-wetting showed that rainfall intensity, varying over the range from 16.5 to 66 mm h-1, had little effect on the decline in surface hydraulic conductivity as a function of cumulative rainfall kinetic energy. This contrasts with greater seal permeability under higher rainfall intensities observed by Romkens et al. (1985) and others. It is proposed that an alternative explanation exists for the observations of Romkens et al. based on reduction in seal permeability due to lower sub-seal water potential under lower intensity rainfall.
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Post-ponding reduction in K[subscript sat] under high kinetic energy rainfall exhibited exponential decline as a function of cumulative raindrop kinetic energy as proposed by Moore (1981b). However, inferred rates of decline prior to ponding were more rapid than measured post-ponding rates suggesting that infiltration models using only a single exponential rate of surface K[subscript sat] decline based on post-ponding measurements may be in error. Potential for error is greatest at early times for loose soil that is highly susceptible to sealing.
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Pre-ponding decline in surface aggregation was also relatively more rapid than post-ponding decline. This discrepancy was evident irrespective of soil pre-wetting. From this it was concluded that the more rapid initial aggregate breakdown and surface sealing was due, at least in part, to processes other than aggregate slaking due to rapid soil wetting. An explanation has been proposed as follows. Raindrops initially fall on aggregates that have not been subjected to rainfall and therefore each drop has the capacity to cause greater aggregate breakdown than subsequent raindrops that fall on aggregates or soil fragments that have been strong enough to survive preceding rainfall impacts. Such a mechanism could provide an alternative explanation of the findings of Baumhardt et al. (1991) who found that less cumulative raindrop kinetic energy was necessary to achieve a given reduction in surface conductance when the cumulative energy was supplied through lower energy drops.
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Relationships predicting rates of surface sealing using aggregate breakdown under rainfall and aggregate stability were evaluated. Post-ponding infiltration rate and surface K[subscript sat] were related to aggregate size by exponential functions. The proportion of surface aggregates less than 0.125 mm in diameter provided slightly more consistent relationships. Parameters of fitted relationships differed among wetting pre-treatments suggesting that the influence of sub-seal water potential on surface K[subscript sat] must be considered whenever such relationships are developed or applied. Aggregate stability determined by wet sieving was related to rainfall volume required for ponding, final K[subscript sat] and final aggregate size but only for initially dry soil suggesting that such relationships may be unique to the rainfall, soils and flow conditions used to develop them.
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This study has established the relative importance of rapid soil wetting and energetic raindrop impact in both aggregate breakdown and surface sealing over a range of antecedent soil water and rainfall conditions. It has quantified the effectiveness of culturally induced aggregate stability in ameliorating effects of these two important agents and illustrated the potentially significant consequences for the soil water balance. It has quantified temporal patterns of surface sealing and aggregate breakdown and proposed an alternative mechanism explaining more rapid aggregate breakdown during the initial stages of rainfall. It has identified possible explanations for effects of rainfall intensity on surface sealing observed in other studies. It has also partially evaluated a mechanism proposed to explain important effects of subseal water potential on seal permeability found in this and other studies. These significant findings have been used with the findings of other studies to amend the conceptual model proposed by Le Bissonnias (1990). The amended model gives a more complete description of the relationships between parameters and processes determining aggregate breakdown and structural surface sealing under rainfall.
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Clivati, Alba Antonia. "A fractal description of the soil aggregate distribution /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488191124568814.
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Rogers, Stephen Lloyd. "The effect of phototrophic microbial inoculants on soil aggregate stability and soil fertility." Thesis, University of Kent, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305060.
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Yesilbas, Gulsah. "Stabilization Of Expansive Soils By Using Aggregate Waste, Rock Powder And Lime." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604950/index.pdf.
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Expansive soils are a worldwide problem that poses several challenges for civil engineers. Such soils swell when given an access to water and shrink when they dry out. The most common and economical method for stabilizing these soils is using admixtures that prevent volume changes. In this study the effect of using rock powder and aggregate waste with lime in reducing the swelling potential is examined. The expansive soil used in this study is prepared in the laboratory by mixturing kaolinite and bentonite. Lime was added to the soil at 0 to 9 percent by weight. Aggregate waste and rock powder were added to the soil at 0 to 25 percent by weight. Grain size distribution, Atterberg limits and swell percent and rate of swell of the mixtures were determined. Specimens were cured for 7 and 28 days. This method of treatment caused a reduction in the swelling potential and the reduction was increased with increasing percent stabilizers.
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Zeng, Weixi. "Assessment of matrix soil improvement using displacement aggregate piers." [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1476359.
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Guidi, Patrizia <1986>. "Biophysical characterization of soil aggregate fractions in different agroecosystems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8377/1/Guidi%20Patrizia%20tesi.pdf.
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Aggregates contribute to determining the structure of the soil and form the physical space and the habitat in which microorganisms live and play their role by regulating soil functioning. Consequently, the study of the biophysical properties of aggregates can be an effective tool for assessing what influence soil management has on its functionality, and especially on carbon sequestration.
Interdisciplinary research on the biophysical properties of aggregates therefore needs to be carried out in order to assess the effect of management on the biophysical properties of different aggregate size classes. In this study we investigated the biophysical parameters of macroaggregates (4-1 mm) mesoaggregates (1-0.25 mm) and microaggregates (<250 μm) in soils under an alfalfa crop and oak wood (representative of a mountain agroecosystem), and under three walnut sites (representative of plain agroecosystem) characterized by differing urea distribution (one site was fertirrigated with 90 kg liquid urea/ha-1, one site received 90 kg granular urea/ha-1, one site acted as the control without urea addition). We assumed that different aggregate classes (different microhabitats) have specific biophysical properties and the spatial relationship between organic matter and pores should be different in aggregate classes, regulating soil carbon sequestration function.
Our biophysical characterization showed that the aggregate classes investigated were easily distinguishable microhabitats. The soil management effects depended on aggregate size. Soil organic matter input and N fertilization affected the soil organic matter availability for microorganisms in macroaggregates. The aggregation process, by contrast, seemed more relevant for the C dynamics in meso- and microaggregates, thus in aggregates <1 mm. Indeed, thin aggregate sections confirmed that mesoaggregates were microhabitats in which a great accumulation of organic matter occurred as stable and transformed amorphous forms, as a result of aggregate genesis.
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Cousen, S. M. L. "The assessment of soil aggregate stability to raindrop impact for some tropical soils material, with particular reference to iron." Thesis, University of Portsmouth, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375487.
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Soil aggregate stability to raindrop impact is df fundamental importance to many aspects of the soil system, in particular rainsplash erosion. This stability has been measured by use of single drop rainfall simulators, the characteristics and operation of which have, in the past, shown considerable variation. The drop sizes, impact frequency, drop fall height, chemistry of drop-forming liquid, aggregate pretreatment, and definition of breakdown affect the way in which the the apparatus can be used to define stability. In this thesis an apparatus is developed that is believed to give results with increased consistency and replicability. An index of stability (F) is evolved from data collected using the raindrop simulator which is then used to characterise a set of iron rich, tropical soils from Kenya and Mo~ambique. Information about the iron, textural, chemical and magnetic status of each soil sample is also collected and used to try to predict the stability index through a process of statistical modelling. Models for highly stable and poorly stable soils are developed and finally a definitive model that can be used for all the soils. The last section of this investigation attempts to try and explain the results in terms of the processes that might be operating in the soil. Specific reference is made to the iron content of the soils because of its natural abundance in the samples considered. The possible contributions of total iron, crystalline iron, amorphous iron and organic iron to aggregate stability are discussed.
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Lucas, Shawn T. "MANAGING SOIL MICROBIAL COMMUNITIES WITH ORGANIC AMENDMENTS TO PROMOTE SOIL AGGREGATE FORMATION AND PLANT HEALTH." UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/24.
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The effects of managing soil with organic amendments were examined with respect to soil microbial community dynamics, macroaggregate formation, and plant physio-genetic responses. The objective was to examine the possibility of managing soil microbial communities via soil management, such that the microbial community would provide agronomic benefits. In part one of this research, effects of three amendments (hairy vetch residue, manure, compost) on soil chemical and microbial properties were examined relative to formation of large macroaggregates in three different soils. Vetch and manure promoted fungal proliferation (measured via two biomarkers: fatty acid methyl ester 18:2ω6c and ergosterol) and also stimulated the greatest macroaggregate formation. In part two of this research, effects of soil management (same amendments as above, inorganic N fertilization, organic production) on soil chemical and microbial properties were examined relative to the expression of nitrogen assimilation and defense response genes in tomato (Solanum lycopersicum L.). Soil management affected expression of a nitrogen assimilation gene (GS1, glutamine synthetase) and several defense-related genes. The GS1 gene was downregulated with inorganic N fertilization, expression of the pathogenesis-related PR1b gene (which codes for the pathogenesis-related PR1b protein) was increased in plants grown in soil amended with compost, vetch, and N fertilizer, and expression of three other defense-related genes coding for chitinase (ChiB), osmotin (Osm), and β-1,3-glucanase (GluA) were decreased in plants from soil amended with manure and in plants from the organically managed soil. Differential expression of defense-related genes was inversely related to the relative abundance of Gram-negative bacteria. The relative abundance of the 18:1ω7c Gram‑negative bacterial biomarker was greatest in manure treated soil and in organically managed soil (which recieves seasonal manure applications). These treatments also had the lowest expression of ChiB, Osm, and GluA, leading to speculation that manure, through increases in Gram-negative bacteria, may have suppressed populations of soil organisms that induce a defense response in plants, possibly allowing for less-stressed plants. Outcomes of this research may be useful for those interested in developing management strategies for maintaining or improving soil structure as well as those interested in understanding management effects plant physio-genetic responses.
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Joshi, Gyawali Ayush. "A fresh soil health perspective: Soil health dynamics and improved measurement techniques." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/89949.
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Encouraging greater implementation of conservation agriculture practices such as reduced tillage and cover crops may require better understanding of the effect of these practices on soil health. The overall objective of this study was to quantify soil health dynamics due to conservation agriculture practices and address methodological gaps in terms of measuring soil health parameters. We developed five sites across the state of Virginia; each site had replicated plots with combinations of reduced tillage versus disk tillage and wintertime cover crops versus no cover crops as experimental treatments. Soil and plant samples were collected 1-2 times per year for 3 years, and were analyzed for 30 soil health parameters. The parameters were first evaluated to determine if any consistently detected treatment differences. We then quantified the temporal dynamics of the eight most responsive soil health parameters, while considering influences of soil water content at time of tillage, cover crop biomass, and previous land management history.
Of the analyzed parameters, only 2-4 mm aggregate stability and magnesium showed high responsiveness and consistency in identifying tillage and cover crop effects. None of the parameters detected treatment differences in all sites or at all times, yet samples collected after high biomass cover crops or after tillage in wet conditions tended to show significant treatment differences for multiple indicators. The previous history of management in each site may have affected trends in aggregate stability, but did not appear to influence other indicators.
As soil aggregate stability was found to be the most important soil health parameter, our third study developed an improved method for measuring soil aggregate stability. This new method, Integrated Aggregate Stability (IAS), interprets aggregate stability using a laser diffraction machine. Overall, IAS showed higher correlation with the wet sieving method (R2 = 0.49 to 0.59) than widely used median aggregate size (d50) (R2 = 0.09 to 0.27). IAS can also quantify stability of macro- and micro-sized aggregates, which d50 cannot. When comparing between IAS and wet sieving, IAS requires considerably less time and sample amounts.
Our fourth study focused on creating an inexpensive yet accurate tool for measuring soil respiration, as microbial assessments based on respiration rates have great potential for detecting rapid changes in soil health. Using an Arduino-based infrared gas analyzer (IRGA) sensor, we developed the Soil Microbial Activity Assessment Contraption (SMAAC) for less than $150. Our results show that SMAAC provided consistent readings with a commercial IRGA unit when tested using three different configurations.
Altogether, the research presented in this dissertation identifies important soil health parameters and quantifies their temporal and between-site dynamics. Using this narrower set of indicators can help producers and practitioners save resources when conducting measurements to assess soil health effects of agricultural practices. Further, this work also provides improved measurement techniques for useful soil health parameters like aggregate stability and soil respiration. These findings and innovations should help to encourage greater adoption of agricultural management practices that build and preserve soil health.Doctor of Philosophy
If we want to make sure that ample and safe food is available to future generations, then it is time that we produce food without damaging the soil. Many widely used soil management techniques like tillage and leaving the field bare can harm the soil and decrease productivity in the long run. One potential technique to produce food while protecting the soil and environment is conservation agriculture, which can include reduced tillage and cover cropping. Reduced tillage is a technique in which we grow food without majorly disturbing the soil, while cover crops are planted when cash crops are not in the field in order to improve or sustain the soil. Understanding the soil-related benefits of conservation agriculture practices is important to encourage farmers to adopt these practices. In this study we tested the effects on soils of reduced tillage and cover crop practices versus conventional tillage and bare soil practices, using five locations across Virginia. We also developed improved methods for measuring two informative soil parameters. We found that, when looking at all of our five sites, the stability of soil aggregates, the rate at which water enters soil, and the nutrients in surface soils were all affected by the type of management that the soils were subjected to. Reduced tillage increased stability of soil aggregates when compared with conventional till. This increased stability of aggregates indicators lower potential for surface water runoff, erosion, and flooding when we practice reduced tillage. Cover cropping also increased stability of soil aggregates, especially when the cover crops attained substantial above-ground mass. Soil nutrients (which are essential for plants to grow) were also overall higher in the surface soil layers under no-till. Since the stability of soil aggregates was found to be an important benefit of CA practices, we also perceived a need for a better method for measuring stability of these aggregates. In response, we developed a new index called Integrated Aggregate Stability (IAS). IAS was found to give similar results as established methods, but the time required to get IAS result is about 10 minutes, whereas the time required for established methods like wet sieving is around 2 days. IAS measurements are therefore both accurate and quick to perform. We also focused on developing an inexpensive tool for measuring soil respiration. Soil respiration-based measurements help us to understand the activity of microbes in the soil. These microbes are very important for soils to function. Our tool, Soil Microbial Activity Assessment Contraption (SMAAC), was very consistent with a currently used tool and shows high potential for future use. Altogether, we found that no-tillage and cover cropping can increase stability of soil aggregates even within 1-3 years of starting those practices. No-till can also increase nutrient concentrations in the top soil layer. The tools and innovations developed in this study have the potential to increase the ability of farmers to assess soil health and also encourage greater adoption of conservation agriculture practices.
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Adams, Kimberly Ellen. "Influence of Vineyard Floor Management Practices on Soil Aggregate Stability, Total Soil Carbon and Grapevine Yield." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/612.
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Soil aggregates provide pore spaces of various sizes supplying water, gases and nutrients to plant roots and microorganisms, and facilitate moisture retention and availability. Soil aggregate stability is indicative of soil biological and structural health, and is increased by soil carbon derived from plant roots and the soil microbial biomass. Aggregate stability and soil carbon can be enhanced by increasing organic matter through compost additions or by planting cover crops. Additionally, aggregate stability is enhanced by arbuscular mycorrhizal fungi (AMF) that form a symbiotic association with plant roots, and consolidate soil particles into aggregates through hyphal networks and through the production of glomalin, binding soil particles together. The use of herbicides decreases soil carbon as it removes vegetation and the microorganisms associated with it. Soils having poor aggregate stability slake and disperse into primary soil particles becoming dense and subject to erosion when exposed to heavy rains. The use of herbicides amplifies this risk as it removes vegetation, leaving the soil bare, with nothing to absorb rainfall impact.
The effect of vineyard floor management practices on aggregate stability, soil carbon and grapevine fruit yield was studied at two vineyard sites located within the Estrella district of Paso Robles, CA. In late fall of 2008, treatments were applied to the vine line including an herbicide, an herbicide plus compost, a cover crop, a cover crop plus compost and a cover crop plus a fungal inoculant treatment. The control had no herbicides, compost, cover crop, or fungal inoculant applied to it. The cover crop treatments were applied at 30 lbs/ac consisting of a mixture of 20 % blando brome (Bromus hordeaceus), 20 % Zorro fescue (Vulpia myuros), 30 % crimson clover (Trifolium incarnatum) and 30 % subterranean clover (Trifolium subterraneum). Commercially available compost was applied at a rate of five tons per acre. The fungal inoculant was applied at eight pounds per acre, consisting of the AMF: Glomus intraradices, G. mosseae, G. aggregatum and G. etunicatum each at 32 propagules/ cc. Samples were collected in the spring of 2009 and the winter of 2010.
Percent carbon was significantly higher in the areas where compost applications were received (P=0.014). Cover crops did not significantly increase the level of carbon in the soil (P=0.253). Compost and cover crops significantly increased the amount of > 4.0 mm soil aggregates (P=0.004 for compost and P=0.027 for cover crops). Herbicide treatments significantly reduced the amount of > 4.0 mm aggregates (P=0.028). Fungal inoculants had no effect on > 4.0 mm aggregate stability (P=0.361). Compost significantly increased mean fruit weight (P=0.041). These results suggest that the addition of compost and cover crops are an effective way of increasing > 4.0 mm aggregates and compost alone is an effective way to increase soil carbon and fruit yield.
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Mupambwa, Hupenyu Allan. "Winter rotational cover crops effects on soil strength, aggregate stability and water conservation of a hardsetting cambisol in Eastern Cape Province, South Africa." Thesis, University of Fort Hare, 2012. http://hdl.handle.net/10353/453.
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Winter rotational cover crops (WRCC) are often used to boost soil fertility and plant nutrition. However, selection and use of WRCC for soil physical improvement is usually overlooked. The objective of this study was to determine the effects of WRCC on soil strength, aggregate stability and water conservation of a hardsetting soil. The soil physical properties were determined after four rotations of growing monocultures of vetch (Vicia dasycarpa cv. Max), lupin (Lupinus angustifolius cv. Tanjil) and oats (Avena sativa cv. Sederberg) and after two rotations of growing bicultures of oats (Avena sativa cv. Pallinup) and vetch (Vicia dasycarpa cv. Max) across two soil layers, 0 to 15 cm and 15 to 30 cm. The individual WRCC and a weedy fallow constituted the treatments in the monoculture study whilst in the biculture study the various combinations of WRCC namely; 90% oat plus 10% vetch (O90V10); 70% oat plus 30% vetch (O70V30) and 50% oat plus 50% vetch (O50V50) and a weedy fallow constituted the treatments. After four rotations with cover crop monocultures, oats significantly (P ≤ 0.05) reduced penetration resistance (PR) whilst vetch increased PR in both soil layers compared to the weedy fallow control. The effect of the biculture treatments was only experienced within the 15 to 30 cm depth. The treatments O50V50 and O70V30 increased the PR compared to the control. The WRCC in monoculture significantly increased the soil aggregate stability relative to the control in both soil layers. Vetch, lupin and oats resulted in a 41.7%; 20.4% and 15.7% increase in MWD in the 0 to 15 cm soil layer and 47.2%; 44.2% and 39.7% in the 15 to 30 cm depth, respectively. An increase in aggregate stability was associated with increased macro-aggregation. Under the biculture, WRCC slightly increased, non- significantly, the aggregate stability. Both hot water and dilute acid extractable polysaccharides showed no significant correlation with aggregate stability in the two studies. Oats monoculture resulted in a significant difference (P ≤ 0.05) on cumulative infiltration compared to the control. However, after 2 h vetch and lupin showed no significant difference from the control on cumulative infiltration. Oats resulted in a 7.8% increase in final infiltration rate (FIR) whilst vetch and lupin reduced FIR by 9% and 16.7% respectively, compared to the control. Bicultures of oats and vetch significantly (P ≤ 0.05) increased cumulative infiltration compared to the weedy fallow control. A similar significant increase in FIR was also observed under bicultures. The treatments O50V50; O90V10 and O70V30 resulted in a 163.3%; 113.3% and 105.4% increase in FIR respectively, compared to the control. Cover crop monocultures significantly (P ≤ 0.05) increased plant available water (PAW) compared to the weedy fallow, with vetch, oats and lupin resulting in a 28.3%; 22% and 23.9% increase respectively, in PAW. However, no significant differences were observed on PAW after two rotations with bicultures. Compared with winter weedy fallow, WRCC improved most of the soil physical properties under study, with the most suitable results expected under bicultures compared to monocultures. Under CA, selection of WRCC like oats, vetch and lupin, one should therefore take into consideration their effects on soil physical properties as a selection criterion and not biomass and fertility alone.
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Molope, Mishack Bochankge. "Some effects of biological and physical processess on soil aggregate stability." Thesis, University of Stirling, 1985. http://hdl.handle.net/1893/2595.
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The effects of biological and physical processes on the aggregate stability of some weakly structured arable and pasture soils were investigated. Preliminary investigations showed significant correlations between soil organic matter and both wet sieving and turbidimetric methods of aggregate stability; the latter method was chosen on grounds of convenience. Scanning electron microscope pictures showed the presence of both fungi and bacteria when soils were incubated. Growth of fungi, estimated by ergosterol measurement, correspond to temporary stability increases, which could be explained by retention of soil particles within the reticulum of fungal hyphae. The effect disappeared as the fungi were destroyed and replaced by bacteria and actinomycetes. Effects caused by fungi were examined separately, using vancomycin to inhibit bacterial growth, and bacterial effects by using cycloheximide to eliminate fungi. Bacterial growth had little direct effect in stabilising soil aggregates; periodate oxidation showed that polysaccharides produced by bacteria are mainly responsible. To examine the contribution of physical processes to increased stability in remoulded soils biological processes were eliminated by sterilisation. Thixotropic changes made a contribution to age hardening in remoulded aggregates similar in magnitude to biological processes. Thixotropic changes were reversible and accompanied by soil strength and metric water potential changes. Polysaccharides did not contribute to thixotropic aging processes. Remoulded soils were subjected to wetting/drying and freezing/thawing cycles. After 3 to 6 cycles the stability of both sterilised and unsteriliserd soils recovered to that of natural aggregates, suggesting a contribution by thixotropy. Repeated weathering cycles decreased the stability of unsterilised, and more so sterilised, field aggregates suggesting that in the former, bond reformation due to biological activity counteracted the destruction caused by wetting/drying and freezing/thawing.
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Staunton, M. B. S. "The diffusion and reaction of ions in naturally aggregated soils." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375294.
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