For sustained production, organic agriculture depends on plant needs being synchronized with the release of nutrients from organic amendments during decomposition within the soil. Because decomposition is strongly dependent on soil moisture and temperature, nutrient needs may not always be met as planned or synchronous with plant need. Unlike conventional agriculture, fast acting amendments are not readily available. Much of the evidence that vermicompost benefits crop production comes from studies on seed germination and production of starts in greenhouses. Yet, there is a dearth of information derived from field studies. Soil, soil and water nitrogen, plant development, and marketable yield were investigated by implementing field plot trials with both starts grown in greenhouses (Experiment 1) and directly seeded (Experiment 2) crops to test hypotheses on fertility, economics and environmental impacts. Results from Experiment 1 showed that plant production was dramatically increased both in the greenhouse as well as subsequently in the field for vermicompost treatments and directly correlates to economic differences. Results from Experiment 2 show that plant production differences between compost treatments vary by site. There was no significant difference in soil and soil water NO3-N, NH4-N and Total Inorganic Nitrogen (TIN) among treatments, site or experiment. The timely rate of plant development in greenhouse started VC treatments shows great potential to be the first to market with fresh produce when other treatments are still waiting to transplant.

Orientador: Marcílio Vieira Martins Filho / Banca: Diego Silva Siqueira / Banca: Zigomar Menezes de Souza / Banca: Gener Tadeu Pereira / Banca: Renato Farias do Valle Junior / Resumo: No sistema de pousio, o solo é deixado em repouso por um período de tempo muito variável para que o pool de matéria orgânica do solo se recupere e se assemelhe ao encontrado em florestas maduras adjacentes. Para comprovar tal prática foi realizada uma prospecção no Povoado Quilombo de Damásio, Município de Guimarães, Estado do Maranhão onde obteve-se amostras do solo em áreas de pousio com 25, 20, 15, 10, e 5 anos; da área atual cultivada (lavoura) e outra de floresta primária (controle) nas camadas de 0 a 20 e 20 a 40 cm. O sistema de pousio, nas duas profundidades e tempos, apresentou aumentos e perdas de macronutrientes. Pela análise estatística observou-se diferenças significativas nos aportes e perdas de macronutrientes entre os tratamentos (tempos de pousios) nas duas profundidades do solo analisadas. A análise de correlação apresentou associação positiva e negativa para os macronutrientes pesquisados (P, K+, Ca2+ e Mg2+). Ao longo do tempo o sistema de pousio mostrou-se eficiente na recuperação da fertilidade natural do solo / Abstract: In the fallow system, the soil is left undisturbed for a very variable period of time so that the pool of soil organic matter recovers and resembles that found in adjacent mature forests. To prove this practice was carried out a survey in the town of Quilombo Damásio, City of Guimaraes, Maranhao State where soil samples were obtained in fallow areas 25, 20, 15, 10, and five years; the current cultivated area (farming) and other primary forest (control) in the layers 0-20 and 20 to 40 cm. The fallow system at both depths and times, showed increases and macronutrient losses. For the statistical analysis we observed significant differences in contributions and loss of nutrients between treatments (fallow times) in both soil depths analyzed. The correlation analysis showed a positive association and negative for respondents macronutrients (P, K+, Ca2+ and Mg2+). Over time the fallow system was efficient in the recovery of natural soil fertility / Doutor

Made available in DSpace on 2014-06-11T19:31:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-04-15Bitstream added on 2014-06-13T19:40:44Z : No. of bitstreams: 1 dantas_js_dr_jabo.pdf: 1859485 bytes, checksum: bc0c2c6d72f0f0f6273c30197888337c (MD5) / O avanço tecnológico e o desenvolvimento da agricultura têm aumentado a demanda por informações detalhadas dos solos e seus atributos. O presente trabalho teve como objetivos identificar a ocorrência de solos coesos e estudar suas relações com a paisagem, bem como predizer a erodibilidade de Argissolos coesos na região leste do Estado do Maranhão, em diferentes pedoformas, por meio da determinação dos componentes da cor do solo, utilizando a espectroscopia de reflectância difusa. Foram abertas três trincheiras (perfis 1, 2 e 3), relacionadas a três distintas formações vegetais, para a caracterização morfológica, física, química e mineralógica. Para a predição da erodibilidade, foram selecionadas três áreas cultivadas com soja, onde de cada área, foram retiradas 121 amostras na profundidade de 0,00 – 0,20 m. Para a determinação da reflectância difusa na faixa do visível (380 a 780 nm), foi utilizado 0,5 g de cada amostra, moída e seca ao ar, a partir do qual foram determinados os valores do matiz, valor e croma. De posse destes constituintes da cor, foi calculado o índice de avermelhamento para cada amostra. Foram desenvolvidos modelos para avaliar o efeito de cada componente da cor sobre a erodibilidade em entressulcos (Ki) e em sulcos (Kr), que apresentaram R2 variando de 0,37 a 0,70. Os modelos gerados quando comparados ao de Flanagan e Livingston obtiveram R2 de 0,70 e 0,73, para Ki e Kr, respectivamente. Os resultados demonstraram que a caulinita foi o mineral predominante nos horizontes coesos, porém seu grau de cristalinidade não influenciou na variação da densidade do solo (1,40 a 1,58 g cm-3) e na resistência à penetração (0,68 a 2,18 MPa). A posição da paisagem foi determinante para a distinção dos solos coesos, sendo aqueles desenvolvidos em pedoforma côncava os que apresentaram... / Technological advances and the development of agriculture has increased the demand for detailed soil and its attributes. This study aimed to identify the occurrence of cohesive soils and relationship with its properties with the landscape to predict the erodibility by Ultisols cohesive in the region east of State Maranhão, different landforms using components of soil color characterized by diffuse reflectance spectroscopy. Three trenches were dug (depth profiles 1, 2 and 3) related to three distinct vegetation types, for morphological, physical, chemical and mineralogical. For predicting erodibility selected three areas cultivated with soybeans, those areas 121 soil samples were taken in depth from 0,00 to 0,20 m. 0,5 g of each sample, milled and air dried, values were determined from reflectance in the visible range (380 - 780 nm), from which was determined the values of hue, chroma values. From these spectro components, we calculated the redness index for each sample. Models were developed to evaluate the effect of each component of the color on the erodibility interrill (Ki) and grooves (Kr), showed that R2 ranging from 0,37 to 0,70. The models compared to Flanagan and Livingston obtained R2 of 0,70 and 0,73 for Ki and Kr, respectively. The results demonstrated the kaolinite was the predominant mineral in cohesive layers, but its degree of crystallinity did not influence the changes in soil density (1,40 to 1,58 g cm-3) and penetration resistance (0,68 to 2,18 MPa). The landscape position was essential to the distinction of cohesive soils, and those established in concave landform presented the highest expression of the cohesive character, which resulted in higher soil fertility and organic matter reflecting the more exuberant vegetation characterized by Cerradão. That the constituents of the color thus obtained... (Complete abstract click electronic access below)

Natural and accelerated erosion from trail users affects the sustainability of trail systems. Designing and building sustainable trail systems will greatly decrease the effect that erosion has on a trail. Trails that allow multiple types of users, such as hiking and mountain biking, must be able to sustain both groups. At East Tennessee State University the trail system was originally designed for hiking. Mountain bikers have become the main user group on the trail system leading to erosion problems on certain areas of the trail due to trail design flaws. The study seeks to identify the problem areas of trail and make recommendations towards correcting the trail in order for the trail system to adequately sustain both hikers and mountain bikers on the East Tennessee State University trail system.

Thesis (Ph.D. (Agriculture)) -- University of Limpopo, 2018 / Surface coal mining requires good and sound rehabilitation practices to re-establish productive land capability and land use after mine-closure. The vast majority of Mpumalanga’s coal deposits are located below high quality and productive arable land. Impacts on soil and land, associated with surface coal mining can reduce the possibility to re-establish the pre-mining land capability and productive potential. Stockpiled soils are excavated from the ground during mining activities, and piled on the surface of the soil for rehabilitation purposes. These soils are often characterized by low Soil Organic Matter (SOM) content, low fertility, and poor physical, chemical and biological properties, limiting their capability for sustainable vegetation growth. The aim of this study was to assess coal-mine stockpile soil quality and its impacts on vegetation using laboratory techniques and Reflectance Spectroscopy. Firstly, the impact of quality of coal-mine stockpile soils on sustainable vegetation growth and productivity was investigated. Soils were collected at three different depths (surface (0-25cm), mid (150-200cm) and deep (300-350cm)), as well as mixed (equal proportion of surface, mid and deep) from two stockpiles (named stockpile 1: aged 10 and stockpile 2:20 years) at the coal mine near Witbank in Mpumalanga Province, South Africa. Soils were amended with different organic and inorganic fertilizer. A 2 x 4 x 5 factorial experiment in a randomized complete block design with four replications was established under greenhouse condition. A grass species (Digiteria eriantha) was planted in pots with unamends and amended soils under the greenhouse condition at ambient temperatures of 26-280C during the day and 16.5-18.50C at night. Mean values of plant height, plant cover, total fresh biomass (roots, stems and leaves) and total dry biomass were found to be higher in the stockpile 1 than in stockpile 2 soils. On average, plants grown on soils with amendments yielded plant height that was 98.28% higher than plants grown on soil with no amendment. On average, height of plants grown on soil amended with poultry manure and lime was 44.65% higher compared to plants planted on soils amended with NPK + lime, compost and poultry manure. On average, mixed soils had better vegetation growth than soil from the individual depths. In total, dry biomass and plant height of plants grown on mixed soils was 33.56% and 22.34% higher than plants grown on surface, mid and deep soils. Mixing soils changes texture, which might affect other physical properties like water availability, infiltration rate and aeration and, to some extent, chemical properties.Secondly, the effect of soil amendments on enzyme activity of coal-mine stockpile soil was investigated. The activity of β-glucosidase, alkaline phosphatase, acid phosphatase and urease was analysed after harvest of grass species (Digiteria eriantha). The results show significantly high activity for β-glucosidase, alkaline phosphatase and urease when soils were amended with poultry manure + lime. Soils with no fertilizer yielded significantly low enzyme activity compared to soil amended with poultry manure+ lime, NPK + lime, sole application of poultry and in some instances compost application. β-glucosidase, urease and acid phosphatase mean values generally tend to decrease with an increase in soil depth. β-glucosidase activity for surface soil was found to be 18.06% higher than that of mid and deep soil. The stockpile depth plays a major role in biochemical activities of the soil; deep soils, in most cases, have decreased microbial biomass and enzyme activity due to oxygen and moisture availability. The results for the effect of organic and inorganic amendment on stockpile soil showed that on average, alkaline phosphatase activity following the application of poultry manure + lime was 17.69% higher than that of lime + inorganic fertilizers (NPK). On average, the acid phosphatase activity following the application of lime + NPK was 56.33% higher than that of poultry manure + lime, compost, soil with no fertilizer as well as sole poultry manure. Urease activity for soil with no fertilizer was found to be 84.70% lower than that of soil amended with poultry + lime. The increase in enzyme activity was attributed to change in soil pH due to application of amendments. A comparison of the two stockpiles indicated that, stockpile 2 (20-year old) had low enzyme activity compared to stockpile 1 (10-year old). The activity of β-glucosidase, acid phosphatase, alkaline phosphatase and urease was found to be 11.03%, 8.04%, 10.03% and 60.23% respectively, higher on stockpile 1, relative to stockpile 2 soils. When soils are stockpiled for a long period of time, microbial biomass is reduced and that affect enzyme activity because microbial biomass is considered as the primary source of enzymes in the soil. Thirdly, the capability to estimate coal-mine stockpile soil properties using Reflectance Spectroscopy was investigated. Soil from coal-mine stockpiles were air dried, crushed, sieved and analysed using laboratory methods. The following soil properties: exchangeable calcium (Ca), sodium (Na), magnesium (Mg), potassium (K), soil pH, organic carbon (OC), phosphorus (P) and clay content were analysed as they are important for vegetation re-establishment during rehabilitation. Spectral reflectance of the soil samples was measured using FieldSpec 3 Portable Analytical Spectral Device (ASD®) spectrometer. Partial Least Square Regression (PLSR) was used to estimate various soil properties, in combination with various spectral transformation techniques such as untransformed reflectance spectra, First Derivative Reflectance (FD) and Log transformed spectra Log (1/R). To assess the performance of various predictive models, R2 (Coefficient of Determination), Root Mean Squares Error of Validation (RMSEV) and Variable Importance in the Projection (VIP) values were computed. The results showed that pH and Ca were accurately estimated (R2=0.79 and 0.69 and RMSEV=0.52 and 0.89cmol/kg respectively) using Log (1/R) reflectance as compared to other soil properties achieving R2 less than 0.5. Ca has strong correlation with pH. Ca expressed in soil solutions is mostly related to pH, which is what was attributed to accurate prediction of both Ca and pH. Soil pH in most cases is directly influenced by calcium carbonate content in the soil. Although the performance of other soil properties was poor, they were highly correlated with pH and Ca except for K. K is soluble and mobile and is therefore subject to leaching in most soils resulting in low K concentrations. Low K concentrations results in higher variability and lower R2 values.Finally, the capability of Partial Least Square Regression and Reflectance Spectroscopy to estimate the effect of coal-mine stockpile soil on foliar nitrogen and phosphorus content was investigated. Grass samples were collected from coal-mine stockpile soils and the adjacent unmined soils at open-cast coal mine around Witbank area in Mpumalanga Province, South Africa. Samples were oven dried and analysed for foliar N and P concentration in the laboratory. Spectral reflectance of the dried grass samples were measured using Analytical Spectral Device (ASD) - FieldSpec 3. Partial Least Square.Regression (PLSR) was used to estimate N and P concentration, in combination with various spectral transformation techniques such as First Derivative Reflectance (FDR) and Log transformed spectra Log (1/R). The results show that stockpile soils appear to impact foliar N and P concentration as evidenced by low N and P concentration in the grass, sampled from stockpile soils compared to grass sampled from unmined soils. This was attributed to soil nutrient status of the study sites, as unmined sites had high soil nutrient content than stockpile soils. Foliar N concentration of grass sampled from stockpile soils and unmined soils can accurately be estimated without spectral transformation. FD yielded highest R2 for N and P estimation in grass sampled from both stockpile soils and unmined soils.Overall, the study shows that stockpiling affect soil quality, enzyme activity and vegetation growth. It further shows that soil amendments can improve soil quality and enzyme activity of coal-mine stockpile soils. Finally, Reflectance Spectroscopy can be used to estimate coal-mine stockpile soil properties, its quality and foliar N and P content as an indicator of vegetation nutrient stress. / National Research Foundation

Extensive research has been carried out in both field and laboratory to explain water and solute movement under both saturated and unsaturated conditions. The importance of such work is obvious, since any attempt at exploring land reclamation by leaching or nutrient movement in plant feeding (to name only two) is subject to interpretations and theories of moisture flow. Water flow through soil during reclamation by leaching can be termed miscible displacement since soil water and leaching water do not have a distinct fluid-fluid interface and will physically mix. It is probable that miscible displacement investigations can contribute to an understanding of time-ion concentration relationships in land drainage. Much work is and has been done in the laboratory on moisture flow with particular reference to miscible displacement theories. This project investigates a portion of the overall miscible displacement phenomena in the field under conditions which would exist in practice. Specifically, an attempt is made to determine the relative importance of hydrodynamic dispersion and diffusion in a tile drained soil over a relatively impermeable clay using chloride as a tracer.

The concern about the environment has required that the effects of drilling fluids (muds) on surrounding areas be known. This study was initiated to investigate the effects of various muds on plant growth and on soils. In preliminary studies in Phase I (31 individual mud components), it was concluded that the obvious dominant effects on plant growth of detrimental drilling fluid components included excess soluble salts, excess exchangeable sodium percentage, possibly a high pH in some mixtures, and undesirable physical conditions. The latter resulted from the sodium and/or starch, gums, and bentonite. Phase II, the second year's study of the effect of drilling fluid on six soils and on the plant growth (which is this report) was designed to use seven typical drilling fluids at ratios of 1:4 (called the low rate), and 1:1 (called the high rate) by volume of liquid mud to disturbed and settled soils using green beans and sweet corn as the test plants. The seven mud mixtures were potassium chloride mud (PCM), diesel oil emulsion mud (DOEM), high pH lime mud (HPLM), lignite lignosulfonate sodium mud (LLSM), lignite lignosulfonate potassium mud (LLPM), dichromate mud (DTM), and a mud base (MB). Each mud contained bentonite and barite plus sodium or potassium hydroxide plus a few other substances. Too much soluble salts or too high an exchangeable sodium percentage was the major cause of reduced plant growth. The dispersing problem of mud-treated soils caused by high exchangeable sodium percentages results from the high sodium hydroxide contents added to the muds. Early attempts at leaching the soils with tap water were unsuccessful because of low permeability. Releaching all samples finally with salty water, first with 1 percent Ca(NO3)2, and later with 0.2 percent Ca(NO3)2, and finally with tap water was effective and plant growth improved in all mud mixtures. In unleached treatments the muds PCM, DOEM, and DTM were most limiting to plants growth. Reclamation of soils into which drilling fluids (muds) are mixed seems to require primarily (1) the removal of excess salts, and (2) a lowering of the content of exchangeable sodium with some additions of chemical amendments (calcium salts) and adequate leaching.

The objective of this study was to evaluate response times of a salinity sensor and a soil psychrometer. Influences of pressure, temperature and molar concentration changes were to be measured. Salinity sensor response times ranged from 50 to 130 minutes during solution adsorption while desorption response times were perhaps ten times as long. Temperature affected both response times and equilibrium values, but pressure did not affect either. Soil psychrometer response times ranged from from 40 to 80 minutes for either adsorption or desorption of solution. However, other factors probably related to indirectness of measurement made the soil psychrometer fail to reflect osmotic potential. Both pressure and temperature effects were significant. Comparisons between hypothetical soil water infiltration times and sensor response times together with soil psychrometer failure led to the conclusion that the salinity sensor may be useful while the soil psychrometer would probably not be useful for the return-flow water quality control.

With the dramatic expansion of pinyon-juniper woodlands over the last century, improved understanding of how these woodlands modify infiltration properties is needed, in order for land managers to make informed decisions on how to best manage their specific resources. However, current methods for measuring soil infiltration are often limited by low sample sizes and high experimental error, due to constraints associated with remote, non agricultural settings. This thesis first presents a scheme for automating and calibrating two commercially available infiltrometers, which allows collection of a large number of precise unsaturated infiltration measurements in a relatively short period of time. Secondly, a new method to precisely determine saturated hydraulic conductivity from small intact soil cores collected in the field is demonstrated. This method removes bias due to measurement error using a multiple head linear regression approach. Finally, hundreds of fine spatial scale measurements of soil sorptivity, unsaturated hydraulic conductivity, saturated hydraulic conductivity, soil water content, and other soil descriptive measurements along radial line transects extending out from the trunk of juniper (Juniperus osteosperma) and pinyon pine (Pinus edulis) trees. Within the subcanopy of these trees, interactions among litter material, root distributions, and hydrophobic soil significantly influence ecohydrologic properties by limiting and redirecting infiltration below the soil surface. Consequently, hydrophobicity appears to be a mechanism that promotes survival of woody vegetation in arid environments, through decreasing evaporation rates from the soil surface. We further demonstrate how differences in unsaturated infiltration and soil water content between the subcanopy and intercanopy zones are not discrete. Unsaturated infiltration was significantly lower within the subcanopy than in the intercanopy, and increased by eight-fold across a gradient extending outward from near the edge of the canopy to approximately two times the canopy radius. This gradient was not strongly related to soil moisture. In the intercanopy, increasing structural development of biological soil crust cover beyond this gradient was positivity correlated with infiltration capacity. Consequently, these results indicate that the spatial location of the trees should be considered in the assessment and modeling of woody plant and biological soil crust influence on infiltration capacity in a pinyon-juniper ecosystem.

Soil-reinforcement technology has become an acceptable approach for constructing earth structures. Development in the industry of polymer based reinforcements (geosynthetics) provided the necessary products to advance this technology Limit state design of soil-reinforced continuum does not account for the characteristic kinematic and constitutive behavior of the different elements that constitute a reinforced-soil mass. In the mean time, finite element modeling, which is a powerful numerical tool, provides a scheme of analysis that is capable of predicting the overall performance of a reinforced-soil continuum. Different finite element models have been reported in the literature for modeling soil/geosynthetic interaction in reinforced-earth structures. However, most of these attempts do not fully represent the possible modes of shear mobilization that may develop along different types of soil/geosynthetic interfaces. Possible numerical problems were also associated with most of these models This research provides a new approach for the finite element modeling of soil/geosynthetic interaction in reinforced earth works. The proposed approach is based on the actual interaction behavior experienced in different experimental and theoretical studies presented in the literature over the past three decades The model was numerically tested versus the results of actual laboratory and field tests conducted on soil/geotextile and soil/geogrid pullout tests. The results of the numerical analyses complied with the actual measurements indicating the reliability of the model. A new computer program, TU-INTERACT incorporating the new model, was developed to simulate the behavior of full-scale reinforced-earth structures. The program was used to perform a class-C prediction for the field behavior of a full-scale test section of a levee located in New Orleans, Louisiana. The numerical model yielded good predictions of the field measurements A parametric study was conducted on virtual scenarios to investigate the effect of the different control parameters of soil/geosynthetic interactions on the overall behavior of reinforced-soil masses, and to further examine the sensitivity of the proposed model to the changes in such parameters. Results of this study yielded logical behavior that conformed with the expected real performance of reinforced earth structures / acase@tulane.edu