No description available.

A study was made of the physical properties of a number of structurally sensitive soils some of which exhibited behaviour characteristic of hard-setting soils (soils which when wet slump and set hard, on drying presenting problems in terms of ease of cultivations and root growth). Work concentrated on an examination of soils of the Wick series at two sites at the Institute of Horticultural Research, Wellesbourne, where there is a documented history of consistent differences in crop yields between sites. The worse site (Big Ground) had been intensively managed for considerably longer than the better one (Plum Orchard). Dry bulk density measurements over the growing season suggest that slumping occurred on both sites. Big Ground had the greatest bulk density (typically over 1.65 g/cm3). Field and laboratory penetrometer measurements have shown that under relatively dry (an 8% moisture content) conditions roots would experience severe mechanical impedence on both sites. Root counts at final harvest showed that conditions for rooting were considerably worse in Big Ground where all roots were confined to the top 30 cm. Root growth was better in Plum Orchard and was concentrated in between peds, which did not exist at Big Ground. Laboratory strength (unconfined compressive and indirect tensile) and friability measurements on equilibrated samples also showed up differences between the two sites; the greates differences existing between 1 and 10 bar tension with Big Ground samples exhibiting the greatest strengths and least friabilities. On both sites strengths were observed to increase sharply for a comparatively small decrease in moisture content. Implications of these results are discussed with reference to ease of cultivation and rootability. Another light texured soil from Elgin, known for its tendency to erode, was chosen as a contrast to the Wellesbourne sites. Soil at this site was shown to have much less of a tendency to slump and to create problems for root growth, compared to the Wellesbourne sites. The Elgin soil was also considerably weaker, and the sharp increase in strength observed at Wellesbourne was not observed in Elgin. A new test for water suspendable solids, performed on the Wellesbourne and Elgin soils as well as on 5 other soils known for their structural instability showed that, with the exception of the Elgin soil, a large amount of silt sized material could be brought into suspension with little soild disturbance. An explanation for hard-setting behaviour which is based on those results is suggested.

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 53-54).

Subsoiling and deep loosening are widely used to alleviate soil compaction but little is known about the mechanics of the compaction process. Further information is required on the process that soil goes through during compaction, along with the effect on the amount of soil compaction of various tyre configurations. Such information will allow more confident recommendations to farmers on the suceptability of their soil to compaction. Experimental work was conducted where the soil deformtions of a light textured soil were monitored throughout the whole soil mass. The deformations in the soil were caused by a loaded pneumtic tyre on the surface. In the experimental work, both the process of soil compaction and the final state of the soil following the passage of a wheel were monitored. The experiments showed that soil compaction on light textured soils is caused by a punch failure of the soil, therefore most of the compaction is confined to the area directly below the wheel. The experimental monitoring of soil deformations was a slow and complex process, drawing firm conclusions from the work was further complicated by the interactions of the input variables, such as load and contact length. In order to monitor the effect of individual inputs on soil compaction a thre dimensional mathematical model of the process was developed from Theories of Elasticity and a confined compression soil test. The model predicted the subsurface deformations in the three principle directions due to surface loads. Once the model was modified to account for the support capability of the soil it proved it could, with resonable accuracy, predict the defomations and hence soil canpaction due to a tyre on the soil surface. The model was used to predict the effect of various tyre configurations on soil ccrnpaction. From a number of these runs it was possible to find the sensitivity of soil to compaction due to that input. The results showed that the sensitivity of soil to ccmpaction is not a linear relationship and significant reductions in the amount of soil, canpacted and the level of ihe compaction can be achieved by the right tyre configuration.

No description available.

Thesis (DTech (Environmental-health))--Cape Peninsula University of Technology, 2018. / The management of agricultural soil and its sustainable use, namely productivity, is paramount to the agricultural industry worldwide. Large-scale agricultural product producers and scientists emphasise using environmentally benign methods to increase agricultural production such as taking a green chemistry approach to agricultural activities and/or using cultivation techniques for the bio-augmentation of agricultural soil. Some of these agricultural products, such as cassava (Manihot esculenta), produce cyanogens which promote the infestation of a cyanogen-resistant microbial species known to produce mycotoxins during decomposition. Although cyanogens and mycotoxins are important components in the functioning of the earth system and agricultural soil, their cumulative effects can result in reduced soil productivity, hence degradation. Furthermore, the presence of mycotoxins in the environment and agricultural produce is hazardous to the environment, including the biotic communities in soil and humans. Therefore, an environmentally benign (green chemistry approach) method for the reduction of cyanogens and mycotoxins was proposed for this research study. The method investigated had to be applicable in-situ for the biodegradation of cyanogens and mycotoxins. Their reduction from decomposing cassava in cultivated soil, which can be used on a small and large scale, would mitigate deleterious effects of a less reported, unknown mycotoxins producer (fungal species), Cunninghamella bertholletiae (KT275316), found to be a free cyanide- (CN-) resistant isolate. The C. bertholletiae was isolated from decomposing cassava tubers and silt, subsequent to culturing on potato dextrose agar (PDA) and in an equivalent volume of nutrient broth (NB) containing KCN (4mg/40mL) at 30 °C for 120 hrs. The isolate demonstrated an ability to biodegrade CN- into NH3 and NO3. NH3 and NO3 are nitrogenous by-products produced when young cassava plants are cultivated in a controlled environment, with 80% of the initial CN- concentration being efficiently degraded to NH3/NO3 at a conversion rate of 77.5% and 72.5% (fungus from silt and cassava), respectively, within 120 hrs. From this research, it was observed that Sub-Saharan Africa is the largest contributor to the CN- load into the environment; from cassava cultivation as per FAO data. The quantity of CN- released was estimated at 0.025x10-3 to 6.71 ppq, with further increases of 60.5% being projected to be released into the environment by 2024. As such, it was hypothetically assumed that numerous species in cassava-cultivated soil become CN- resistant as they are exposed to CN- from decomposing cassava, becoming pathogenic thus antigonistic towards other biota in cassava-cultivated soil. Consequently, the pathogenicity of the isolate was investigated against organisms (n = 12) from cassava-cultivated soil. The isolate demonstrated inhibitory pathogenic activity against some soil bacterial communities such as Oligella ureolytica, Acinetobacter sp., Pseudomonas luteola and Sphingomonas paucimobilis. The isolate also demonstrated minor antagonistic effects against Myroides sp., Stenotrophomonas maltophilia, Candida lipolytica, Cryptococcus albidus and Rhodotorula sp.. Further research to identify extracellular metabolites produced by this organism, using a fermentation method was also carried out using a liquid state fermentation technique. 30 mL Erlenmeyer flasks containing 25 mL of NB/KCN (source of CN-) at 37 °C for 168 hrs, with a volume of (5 mL), extracts from the fermentation being filtered, centrifuged, mixed with chloroform for a liquid-liquid extraction procedure subsequent to a nitrogen-facilitated blow-down technique and reconstitution with 100% analytical grade methanol, for LC/MS-TOF 6230 analysis. The analysis revealed that the isolate was able to produce the mycotoxins/secondary metabolites, Fumonisin B1 (FB1) and Deoxynivalenol (DON). Though the isolate (KT275316) demonstrated the ability to biodegrade cyanide as well as produce mycotoxin, an environmentally benign strategy (green chemistry method) with a potential to biodegrade CN-/NH3/NO3/NO2 for the biodegradation of mycotoxins was evaluated, including the identification of biodegradation by-products post-biodegradation treatment. Thus, plant extracts from Nepenthes mirabilis were found to contain enzymes such as carboxylesterase, β-glucosidase, β-glucoronidase and phosphatidyl inositol phospholipase C (identified using both quantitative and qualitative methods). The plant extracts were used with treated samples from the fermentation and were subjected to biodegradation. Thus, resulting in biodegradation by-products such as Heptadecanone Octadecanamide, Octadecenal for FB1 and Tolmetin for DON, respectively. For future research, it is therefore recommended that plant extracts with similar properties to those observed for N. mirabilis extracts (juice) be sought for application of the proposed method.

Agricultural soil properties exhibit variation over field plot scales that can ultimately effect the yield. This study performs multiple spatial pattern analyses in order to design spatially dependent regression models to better understand the interaction between these soil properties. The Cation Exchange Capacity (CEC) and Calcium-Magnesium Ratio (CaMgR) are analyzed with respect to Calcium, Magnesium, and soil moisture values. The CEC and CaMgR are then used to determine impact on the yield values present for the field. Results of this study show a significant measure of model parsimony (0.979) for the Geographically Weighted Regression (GWR) model of the CEC with free Ca, Mg, and soil moisture as explanatory variables. The model for CaMgR using the same explanatory variables has a much lower measure of model fit. The yield model using the CEC and CaMgR as explanatory variables is also low, which is representative of the underlying processes also impacting yield.

As culturas do milho e da soja respondem pela maior parte da produção nacional de grãos, predominando o sistema de plantio direto. Para uma semeadura direta de qualidade, o bom aterramento do sulco é indispensável, pois garante um ambiente adequado às sementes. Neste sentido, é importante estimar a mobilização de solo promovida por uma haste sulcadora estreita durante esta operação. O modelo analítico existente visa representar a mobilização do solo no sistema de plantio convencional. Como consequência, há situações em que este não pode se aplicado, como no caso de hastes sulcadoras estreitas utilizadas em semeadoras de plantio direto. Nestas situações, o mecanismo de falha do solo pode se alterar, assumindo um comportamento não modelado na literatura. Essa pesquisa propõe um modelo fuzzy capaz de representar estas situações, aproveitando conhecimento da teoria de mecânica dos solos e da análise de resultados experimentais. No modelo proposto, parte das regras descrevem situações não abrangidas pelo modelo analítico, as quais foram formuladas a partir da estimativa das prováveis áreas de solo mobilizado. O modelo fuzzy foi testado com dados de experimentos conduzidos durante a pesquisa, em duas condições de granulometria de solo (arenoso e argiloso). O modelo proposto reproduziu as tendências observadas nos dados experimentais, mas superestimou os valores de área observados, sendo esse efeito bem mais intenso para os dados do experimento em solo arenoso. A superestimativa ocorreu devido à soma de diversos fatores. Um deles é a diferença entre as leituras experimentais, as quais consideram apenas o solo realmente movimentado, e a premissa do modelo analítico, que considera toda a área de solo incluindo aquela cisalhada, porém não mobilizada. Outro fator foi devido ao efeito do disco de corte da palha, que pré-cisalha o solo à frente da ferramenta. No ensaio em solo arenoso os valores observados de área de solo mobilizado foram menores que os esperados, intensificando o efeito de superestimativa do modelo fuzzy, sendo que este efeito não representa uma deficiência deste modelo. / Soybean and corn crops account for the majority of Brazilian crop production, predominantly under no-till system. A high quality no-till seeding requires adequate furrow finishing to ensure a suitable environment for seed germination and emergence. Therefore, it is important to estimate furrow soil mobilization promoted by a chisel opener during seeding operation. Existing analytical models aim to represent soil mobilization in conventional tillage. As result, there are situations which the model cannot be applied, such as the case of chisel opener of no-till seeders. Under these situations, soil failure mechanism may change assuming a behavior not modeled by other studies yet. This research proposes a fuzzy model to represent these situations, taking advantage of knowledge obtained from soil mechanics theory and analysis of experimental data. In the proposed model, part of the rules describes situations not covered by the analytical model, which were formulated based on the estimation of possible mobilized soil areas. The fuzzy model was tested using data from experiments for two conditions of soil particle size (sandy and clay). The model simulated trends observed in the experimental data but overestimated observed values of area, which effect was much more intense on sandy soil experiment. The overestimation was due a sum of factors. One is the difference between experimental and modeled data, the first only consider the really mobilized soil, while the last consider the whole soil area, including the sheared but not mobilized area. Another factor was the effect of the straw cutting disc, which pre-shear the soil in front of the tool. In sandy soil experiment, observed values of soil disturbed area were lower than expected, overestimating the effect of fuzzy model, which was not a deficiency of the model.

As culturas do milho e da soja respondem pela maior parte da produção nacional de grãos, predominando o sistema de plantio direto. Para uma semeadura direta de qualidade, o bom aterramento do sulco é indispensável, pois garante um ambiente adequado às sementes. Neste sentido, é importante estimar a mobilização de solo promovida por uma haste sulcadora estreita durante esta operação. O modelo analítico existente visa representar a mobilização do solo no sistema de plantio convencional. Como consequência, há situações em que este não pode se aplicado, como no caso de hastes sulcadoras estreitas utilizadas em semeadoras de plantio direto. Nestas situações, o mecanismo de falha do solo pode se alterar, assumindo um comportamento não modelado na literatura. Essa pesquisa propõe um modelo fuzzy capaz de representar estas situações, aproveitando conhecimento da teoria de mecânica dos solos e da análise de resultados experimentais. No modelo proposto, parte das regras descrevem situações não abrangidas pelo modelo analítico, as quais foram formuladas a partir da estimativa das prováveis áreas de solo mobilizado. O modelo fuzzy foi testado com dados de experimentos conduzidos durante a pesquisa, em duas condições de granulometria de solo (arenoso e argiloso). O modelo proposto reproduziu as tendências observadas nos dados experimentais, mas superestimou os valores de área observados, sendo esse efeito bem mais intenso para os dados do experimento em solo arenoso. A superestimativa ocorreu devido à soma de diversos fatores. Um deles é a diferença entre as leituras experimentais, as quais consideram apenas o solo realmente movimentado, e a premissa do modelo analítico, que considera toda a área de solo incluindo aquela cisalhada, porém não mobilizada. Outro fator foi devido ao efeito do disco de corte da palha, que pré-cisalha o solo à frente da ferramenta. No ensaio em solo arenoso os valores observados de área de solo mobilizado foram menores que os esperados, intensificando o efeito de superestimativa do modelo fuzzy, sendo que este efeito não representa uma deficiência deste modelo. / Soybean and corn crops account for the majority of Brazilian crop production, predominantly under no-till system. A high quality no-till seeding requires adequate furrow finishing to ensure a suitable environment for seed germination and emergence. Therefore, it is important to estimate furrow soil mobilization promoted by a chisel opener during seeding operation. Existing analytical models aim to represent soil mobilization in conventional tillage. As result, there are situations which the model cannot be applied, such as the case of chisel opener of no-till seeders. Under these situations, soil failure mechanism may change assuming a behavior not modeled by other studies yet. This research proposes a fuzzy model to represent these situations, taking advantage of knowledge obtained from soil mechanics theory and analysis of experimental data. In the proposed model, part of the rules describes situations not covered by the analytical model, which were formulated based on the estimation of possible mobilized soil areas. The fuzzy model was tested using data from experiments for two conditions of soil particle size (sandy and clay). The model simulated trends observed in the experimental data but overestimated observed values of area, which effect was much more intense on sandy soil experiment. The overestimation was due a sum of factors. One is the difference between experimental and modeled data, the first only consider the really mobilized soil, while the last consider the whole soil area, including the sheared but not mobilized area. Another factor was the effect of the straw cutting disc, which pre-shear the soil in front of the tool. In sandy soil experiment, observed values of soil disturbed area were lower than expected, overestimating the effect of fuzzy model, which was not a deficiency of the model.

Du fait des activités industrielles anciennes et du recyclage croissant des produites résiduaires organiques d’origine urbaine dans les sols agricoles, des composés organiques persistants, parmi lesquels les hydrocarbures aromatiques polycycliques (HAP) se retrouvent présents dans les sols français. Dans le cadre de la gestion des sites et sols pollués et de l'évaluation des risques associés aux HAP dans l'environnement, une meilleure connaissance du comportement, de la dissipation, du transfert ou de l’accumulation des HAP dans les sols est alors indispensable. Dans ce but, il est utile de développer une nouvelle génération de modèles numériques basés sur le couplage flexible de l’ensemble des processus majeurs contrôlant la dynamique des HAP dans le sol. Notre travail repose sur la mise en œuvre, dans le cadre de la plateforme VSoil de l’INRA (https://www6.inra.fr/vsoil/The-Project), d'un modèle global interdisciplinaire de dynamique des HAP dans les sols, applicable à l’échelle du terrain et couplant des modules décrivant les principaux processus physiques, biochimiques et biologiques. Ce modèle associe d’une part des modules déjà publiés simulant la décomposition des matières organiques exogènes apportées, le transfert d'eau, le transfert de chaleur et le transport de solutés dans des conditions climatiques réelles, et d’autre part, un nouveau modèle représentant spécifiquement la réactivité des HAP.La démarche numérique adoptée dans ce travail a alors été de i) calibrer le modèle de terrain en utilisant des paramètres déterminés à partir de données expérimentales obtenues au laboratoire et complétées avec une partie des données de terrain obtenues sur une courte période, ii) tester et valider le modèle calibré au terrain à l'aide des données de terrain complémentaires sur des périodes plus longues, iii) tester différentes hypothèses de variation de disponibilité et scenarios climatiques ou d’apports répétés de différents composts sur le devenir de HAP dans le sol. Nos résultats montrent que le modèle peut prédire de manière satisfaisante le devenir des HAP dans le sol sur une gamme de contamination allant de parcelles agricoles amendées avec des matières organiques faiblement contaminées jusqu’à d’anciens sites industriels fortement contaminés et permettent alors de mieux appréhender les processus contrôlant la dynamique des HAP dans ces différents systèmes. / Due to former industrial activities and the increasing recycling of organic waste products from urban areas in agricultural soils, increasing amounts of persistent organic compounds, among them polycyclic aromatic hydrocarbons (PAH), are to be found in French soils. In the framework of the management of polluted sites and soils and the risk assessment of PAH transfer in the environment, it is essential to better understand the behavior, dissipation, transfer or accumulation of PAH in soils. For this purpose, there is a need to develop a new generation of numerical models based on the flexible coupling between the processes describing PAH dynamics in soil. Our work presents the development and assessment of such model. It is based on the implementation of an interdisciplinary global model, and applicable at the field scale, for PAH in soil by coupling modules describing the major physical, biochemical and biological processes influencing the fate of PAH in soil, with modules that simulate water transfer, heat transfer, solute transport, and organic matter transformation under real climatic conditions. The coupling is performed using the «VSoil» modeling platform of INRA (https://www6.inra.fr/vsoil/The-Project). The steps of our modelling study are the following: i) calibrate the model at the field scale using previously estimated parameters at the lab-scale and completed with field data on a short period of time, ii) test and validate the calibrated model using field experimental data on mid term periods, iii) test different hypotheses of variation of availability and climatic scenarios or repeated applications of different composts on the fate of PAH in soil. Our results show that the model can adequately predict the fate of PAH in soil over a wide range of contamination ranging from agricultural plots amended with weakly contaminated composted organic wastes to old industrial sites heavily contaminated. This new tool allows, therefore, a better understanding of the processes controlling the dynamics of PAH in these different systems.