Fort Hood Military Reservation is a 900 km2 military installation located between Killeen, Copperas Cove, and Gatesville in central Texas. It supports two full armored divisions which require year-round, live-fire maneuvers and training (Ft. Hood, 2003). As a result of the constant foot traffic and use of heavy equipment, the soils on the training ranges have become increasingly compacted, eroded, and stripped of vegetation. This study evaluated the impact that selected soil amendments would have on soil aggregation, infiltration, and levels of glomalin. A field study was done on plots located inside Fort Hood on a Nuff silty clay (fine-silty, carbonatic, thermic Udic Calciustoll). The plots were amended with composted dairy manure, inorganic fertilizers, and native grass seed. Aggregate stability was determined using a wet sieving procedure and total glomalin values were quantified using a Bradford assay. Field measurements of infiltration rates were taken using a drip-type rainfall simulator. Aggregate stability exhibited decreased values over time for all treatments but two (Site Prep / No Seed and Site Prep / Compost / Seed). In addition, three treatments changed significantly over time (from before treatment application to after treatment application). These treatments were the Site Prep / Compost / No Seed, No Prep / No Seed, and No Prep / Seed treatments. Levels of glomalin increased significantly over time for all treatments (p-value <0.001). Glomalin was correlated to aggregate stability after treatments were applied (p-value <0.01) but not before (p-value 0.89). In addition, infiltration rates were not related to glomalin (p-value 0.9) or aggregate stability (p-value 0.09). Additional sampling of Fort Hood beyond the plot study demonstrates significant differences in aggregate stability, infiltration rates, and levels of glomalin. Measurements taken from ten sites showed no correlations between aggregate stability, infiltration rates, or glomalin. Organic C was correlated to percent water stable aggregates (%WSA) and levels of glomalin. These results illustrate the relationship between organic C and aggregate stability as well as glomalin levels in maintaining infiltration rates and reducing soil loss by erosion.

Grasslands throughout the world including those in British Columbia have been severely reduced and altered by agricultural production and inappropriate livestock grazing practices. Ongoing degradation of rangelands is a worldwide problem, currently affecting about 680 million hectares of rangelands. Studies on development and application of criteria and indicators for forests and grasslands are often lacking, or have been done on a limited number of sites with relatively narrow ranges of climate and soil type. This study aims to (i) quantify the relationships among soil/vegetation properties known to be affected by grazing to easily-assessed indicators, used in the existing health assessment systems, that do not require laboratory analyses or time consuming measurement, and (ii) to evaluate impacts of grazing on soil aggregate stability on the rough fescue grasslands of the southern interior of British Columbia. During the growing seasons of 2006 and 2007, soil and vegetation properties were measured on nine open grassland sites with a potential natural plant community dominated by rough fescue (Festuca campestris Rydb.) in the southern interior of British Columbia. Each site had at least one area excluded from grazing and all units were classified into different seral stages according to the amount of rough fescue present on the land. Rough fescue cover was found to be a useful indicator of the presence of functioning recovery mechanisms. Percent exposed mineral soil was found to be a sensitive indicator of the degree of soil stability and watershed function, as well as an indicator of the integrity of nutrient cycles and energy flows in rough fescue grasslands. Percent Junegrass cover was not as sensitive an indicator as percent exposed mineral soil, but has general overall strength with many health measures.. Only the 1-2 mm aggregate size class was closely related to most soil and vegetation properties, showing that it is more sensitive than the other aggregate stability parameters to soil and vegetation properties. The results from this study can help rangeland managers and ranchers in determining the rangeland health in their area as well as help researchers understand that only a certain number of parameters need to be assessed.

Grasslands throughout the world including those in British Columbia have been severely reduced and altered by agricultural production and inappropriate livestock grazing practices. Ongoing degradation of rangelands is a worldwide problem, currently affecting about 680 million hectares of rangelands. Studies on development and application of criteria and indicators for forests and grasslands are often lacking, or have been done on a limited number of sites with relatively narrow ranges of climate and soil type. This study aims to (i) quantify the relationships among soil/vegetation properties known to be affected by grazing to easily-assessed indicators, used in the existing health assessment systems, that do not require laboratory analyses or time consuming measurement, and (ii) to evaluate impacts of grazing on soil aggregate stability on the rough fescue grasslands of the southern interior of British Columbia. During the growing seasons of 2006 and 2007, soil and vegetation properties were measured on nine open grassland sites with a potential natural plant community dominated by rough fescue (Festuca campestris Rydb.) in the southern interior of British Columbia. Each site had at least one area excluded from grazing and all units were classified into different seral stages according to the amount of rough fescue present on the land. Rough fescue cover was found to be a useful indicator of the presence of functioning recovery mechanisms. Percent exposed mineral soil was found to be a sensitive indicator of the degree of soil stability and watershed function, as well as an indicator of the integrity of nutrient cycles and energy flows in rough fescue grasslands. Percent Junegrass cover was not as sensitive an indicator as percent exposed mineral soil, but has general overall strength with many health measures.. Only the 1-2 mm aggregate size class was closely related to most soil and vegetation properties, showing that it is more sensitive than the other aggregate stability parameters to soil and vegetation properties. The results from this study can help rangeland managers and ranchers in determining the rangeland health in their area as well as help researchers understand that only a certain number of parameters need to be assessed.

Grasslands throughout the world including those in British Columbia have been severely reduced and altered by agricultural production and inappropriate livestock grazing practices. Ongoing degradation of rangelands is a worldwide problem, currently affecting about 680 million hectares of rangelands. Studies on development and application of criteria and indicators for forests and grasslands are often lacking, or have been done on a limited number of sites with relatively narrow ranges of climate and soil type. This study aims to (i) quantify the relationships among soil/vegetation properties known to be affected by grazing to easily-assessed indicators, used in the existing health assessment systems, that do not require laboratory analyses or time consuming measurement, and (ii) to evaluate impacts of grazing on soil aggregate stability on the rough fescue grasslands of the southern interior of British Columbia. During the growing seasons of 2006 and 2007, soil and vegetation properties were measured on nine open grassland sites with a potential natural plant community dominated by rough fescue (Festuca campestris Rydb.) in the southern interior of British Columbia. Each site had at least one area excluded from grazing and all units were classified into different seral stages according to the amount of rough fescue present on the land. Rough fescue cover was found to be a useful indicator of the presence of functioning recovery mechanisms. Percent exposed mineral soil was found to be a sensitive indicator of the degree of soil stability and watershed function, as well as an indicator of the integrity of nutrient cycles and energy flows in rough fescue grasslands. Percent Junegrass cover was not as sensitive an indicator as percent exposed mineral soil, but has general overall strength with many health measures.. Only the 1-2 mm aggregate size class was closely related to most soil and vegetation properties, showing that it is more sensitive than the other aggregate stability parameters to soil and vegetation properties. The results from this study can help rangeland managers and ranchers in determining the rangeland health in their area as well as help researchers understand that only a certain number of parameters need to be assessed. / Land and Food Systems, Faculty of / Graduate

Rivers and streams are adversely affected by an increase in sedimentation in their waters from eroding land. High sediment loads in streams can bury fish eggs and prevent hatching, increasing nutrients in the water causing algae blooms, or even contaminating the water with heavy metals carried in or on the aggregates. The erodibility of soil is valuable knowledge to all land users so that we may predict soil loss and its potential to pollute streams. This is done by using the Revised Universal Soil Loss Equation (RUSLE). By predicting soil loss from a given landscape, land managers can take mitigation measures. The precision of the current scale available for soil erodibility (K-factor) by the US Department of Agriculture is not useful to small landowners or on a site-by-site basis. In California’s Central Coast, a grassland hillslope toposequence was investigated in a Los Osos-Diablo soil series complex. Geographic information systems software was used for spatial analysis of variation in the K-factor as well as interpolating areas that were not sampled. Analysis of soils’ particle size, infiltration rate, organic matter content, and structure across the toposequence allowed calculation of the soils’ K-factor values. K-factor values for the footslope, backslope, and shoulder were found to be statistically different from one another. All slope position’s average K-factor values were statistically different than the published Los Osos and Diablo series’ K-factor with the exception of the backslope which was not significantly different than Diablo’s K-factor value. The average of all K-factors was found not to be statistically different than the Los Osos’ K-factor but it was statistically different from the Diablo’s soil series K-factor. The USDA K-factors overestimated the predicted soil loss for the study site.

<p>Cover crop use, especially in no-till systems, is an evolving practice to maintain or improve soil health. There are many possible indicators of soil health, but this study focuses on the analysis of soil aggregate stability, soil active carbon, and soil organic matter. Soil aggregate stability is related to water infiltration and potential for soil erosion, while active carbon serves as an indicator of a readily-available food source for microbial activity, and soil organic matter serves as a mediator for the soil physical, chemical, and biological processes. The sites include: three Purdue Agricultural Centers, two soil and water conservation district sites, 12 farmer sites with conservation cropping systems, and seven conventional comparison sites. The treatments consisted of cover crop versus no cover crop use, or cover crop use with different tillage systems or nitrogen rates. In 2016 and 2017, soil samples were collected at a depth of 0-5 cm, air-dried, and separated into two soil size fractions: 0-2 mm and 2-8 mm. The wet sieve method was used to measure the mean weight diameter of the water stable soil aggregates from the 2-8 mm size fraction in both years. The potassium permanganate method was used to measure the soil active carbon from both size fractions in both years. The dry combustion method was used to measure the soil organic matter from both soil size fractions in 2017 only. Results showed relatively small improvements in soil active carbon and aggregate stability with the addition of three to four years of cover crops to the long-term no-till systems. However, these improvements were greater when comparing the cover crops plus no-till treatments to the conventional-till without cover crops. More work is needed to understand the dynamics of soil aggregate stability, soil active carbon, and soil organic matter in relation to soil health and cover crop use. Cover crops will likely have more impact on soil aggregate stability, active carbon, and organic matter with a longer duration of use.</p><p></p>

Reduced tillage and living mulches are alternative management strategies that can improve soil quality by minimizing disturbance and building soil organic matter. Weed suppression by these two practices alone is often insufficient to avoid crop yield losses, but their performance in an integrated system is not well understood. This project investigated the production of bell pepper (Capsicum annuum L.) and dry bean (Phaseolus vulgaris L.) in conventional tillage and strip tillage with a living mulch of teff (Eragrostis tef Zucc.) and Korean lespedeza (Kummerowia stipulacea Maxim.). Yields of pepper and bean were generally higher under conventional tillage without living mulch. Weed biomass was not influenced by tillage, and was adequately suppressed by teff in a year when conditions for teff growth were favorable. Mowing appeared to suppress weed growth but not living mulch growth. Soil nitrate and ammonium concentration was generally higher under conventional tillage without living mulch. Delaying living mulch seeding by 15 days after crop establishment generally did not affect weed suppression or crop yield. Soil aggregate stability was not consistently affected by tillage or living mulch. Increased mowing frequency, living mulch planting delay, or distance between the crop row and the living mulch may be necessary to achieve acceptable yields with living mulches.

Submitted by Socorro Pontes (socorrop@ufersa.edu.br) on 2016-11-07T15:00:25Z No. of bitstreams: 1 JussiaraSJC_DISSERT.pdf: 2658778 bytes, checksum: b61a9c5bec2c4362f3e2496913b8c2ba (MD5) / Rejected by Vanessa Christiane (referencia@ufersa.edu.br), reason: corrigir on 2016-11-14T13:28:20Z (GMT) / Submitted by Socorro Pontes (socorrop@ufersa.edu.br) on 2016-11-14T15:01:16Z No. of bitstreams: 1 JussiaraSJC_DISSERT.pdf: 2658778 bytes, checksum: b61a9c5bec2c4362f3e2496913b8c2ba (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-01-24T14:34:11Z (GMT) No. of bitstreams: 1 JussiaraSJC_DISSERT.pdf: 2658778 bytes, checksum: b61a9c5bec2c4362f3e2496913b8c2ba (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-01-24T14:34:24Z (GMT) No. of bitstreams: 1 JussiaraSJC_DISSERT.pdf: 2658778 bytes, checksum: b61a9c5bec2c4362f3e2496913b8c2ba (MD5) / Made available in DSpace on 2017-02-15T15:03:12Z (GMT). No. of bitstreams: 1 JussiaraSJC_DISSERT.pdf: 2658778 bytes, checksum: b61a9c5bec2c4362f3e2496913b8c2ba (MD5) Previous issue date: 2016-02-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The absence of plant diversity in agricultural cultivation systems is as extensive and alarming rate of soil degradation. In this context, the research aimed to evaluate the physical and chemical properties of the soil in relation to landscape and agricultural uses to detect which of these attributes were the most sensitive in distinguishing environments. The research was conducted in the city of Martins / RN on site Bela Vista. To characterize the environment in study opening was held three representative profiles and collected soil samples to the diagnostic horizons for physical and chemical analysis of the soil and subsequently classification. six areas were studied: maize consortium, beans and cassava (CON); monoculture of sugarcane (CAN); banana monoculture (BN); monocultures of elephant grass (CE); corn monoculture (MM) and native vegetation as reference (MN). For the study of areas, collected by 6 samples derived from compound 15 replicates for each area mentioned above, the deformed structure with layers of 0.00 to 0.10; 0.10-0.20 and 0.20-0.30 m in order to perform analyzes of the physical and chemical soil. Analyses were performed in the laboratories of Physics and Soil Fertility of the Federal Rural University of Semi-Arid. The textural classification of soils in cultivation environments textural rating ranged Characterizing the environments in profiles as textural rating ranged from sandy clay, clay, and clayish, with pH ranging from acid neutralidade.Verificou low concentrations of exchangeable cations, consequently low base saturation, considered dystrophic. As for agricultural use followed the same trend as fertility, and the grass area elephant showed higher structural quality. The soils were classified in Fluvisols in the fields of sugar cane and elephant grass, consortium, banana and corn and Udorthent the native forest. Textural classification in soil profiles varied from sandy clay, the clay (Neossolos Fluvic), clayey to very clayey (Fluvisol) and sandy clay (Udorthent). Fertility on farming uses showed acidity reactions to the natural forest areas (MN); and Consortium (CON), tending towards neutrality for elephant grass (CE), corn (MM) and Banana (BAN), with the presence of Al3 + and H + Al and without high salinity. The largest Total Organic Carbon (COT) content was in agricultural use of elephant grass (CE) and the consortium (CON) which favored the largest aggregation and aggregate stability in the soil is influenced by soil-landscape relationship. By means of the main components of multivariate analysis demonstrated that some of the chemical characteristics (pH, Ca2+, Mg2+ Sum bases, T, V, CE, Na + and PST were indicators of separation environments). However the most sensitive were (Al 3+, H-Al) / A ausência de diversidade de plantas em sistemas de cultivo agrícolas constitui como uma forma extensiva e preocupante da degradação do solo. Neste contexto, a pesquisa teve como objetivo avaliar os atributos físicos e químicos de um solo em relação a paisagem e usos agrícolas, visando detectar quais desses atributos foram os mais sensíveis na distinção dos ambientes. A pesquisa foi desenvolvida no município de Martins/RN no sítio Bela Vista. Para a caracterização do ambiente em estudo realizou-se a abertura de três perfis representativos e, coletou-se amostras de solos nos horizontes diagnósticos para análises físicas e químicas do solo e posteriormente sua classificação. Foram estudadas seis áreas: consórcio de milho, feijão e mandioca (CON); monocultivo de cana de açúcar (CAN); monocultivo de banana (BN); monocultivo de capim elefante (CE); monocultivo de milho (MM) e mata nativa, como referência (MN). Para o estudo das áreas, coletou-se 6 amostras compostas oriundas de 15 subamostras em cada área supracitadas, com estrutura deformada nas camadas de 0,00-0,10; 0,10-0,20 e 0,20-0,30 m a fim de proceder as análises dos atributos físicos e químicos do solo. As análises foram realizadas nos laboratórios de Física e Fertilidade do Solo da Universidade Federal Rural do Semi-Árido. Quanto a classificação dos solos nos ambientes de cultivo a classificação textural variou dos solos nos ambientes de cultivo a classificação textural variou caracterizando os ambientes nos perfis quanto a classificação textural variou de argilo arenosa, argilosa e muito argilosa, com pH variando de ácido a neutralidade.Verificou-se baixas concentrações de bases trocáveis, consequentemente baixa saturação por bases, considerados distróficos. Quanto aos usos agrícolas seguiu a mesma tendência quanto a fertilidade, sendo que na área de capim elefante apresentou maior qualidade estrutural. Os solos foram classificados em Neossolos Flúvicos nas áreas de cana de açúcar e capim elefante, consórcio, banana e milho e Neossolo Litólico na mata nativa. A classificação textural nos perfis de solo variou de argila arenosa, a argilosa (Neossolos Flúvico), argiloso a muito argiloso (Neossolo Flúvico) e argilo arenoso (Neossolo Litólico). A fertilidade quanto aos usos agrícolas apresentaram reações de acidez para as áreas de Mata Nativa (MN); e Consórcio (CON), tendendo a neutralidade para o Capim Elefante (CE), Milho (MM) e Banana (BAN), com presença de Al3+ e H+Al e sem elevada salinidade. O maior teor de Carbono Orgânico Total (COT) foi nos usos agrícolas de Capim Elefante (CE) e o consórcio (CON) o que favoreceu a maior agregação e estabilidade de agregados no solo, sendo influenciado pela relação solo-paisagem. Por meio dos componentes principais da análise multivariada demostraram-se que alguns dos atributos químicos (pH, Ca2+, Mg2+, Soma de bases, t, V, CE, Na+ e PST foram indicadores da separação dos ambientes). Todavia os mais sensíveis foram (Al3+; H-Al) / 2016-11-01

Since agriculture began, field management has been at the forefront of expanding food production beyond previous limitations. Agricultural productivity is closely related to the physical, chemical, and biological properties of the soil. Landscape position and field management are among primary factors affecting these soil properties. Delineation of topographic positions of the field surface by shape (i.e., convex, concave, and linear) characterizes areas that may accumulate or lose soil and nutrients either during a discrete event or cumulatively over several growing seasons. Increased soil compaction, degradation of soil structure, and erosion have all been attributed to declining agricultural production. In addition to the physical disturbance from cultivation, erosion and deposition of soil components in different landscape positions explain a large part of the heterogeneity of soil properties across an agriculture field. In response to this, conservation tillage techniques, precision agriculture, and other novel management strategies have been developed to reduce negative impacts conventional row crop production such as nutrient pollution and compaction while optimizing farmer inputs. The objective of this project was to evaluate effects of topographic position and conservation tillage techniques on soil physical, chemical, and biological properties on the field scale as well as correlate certain soil attributes with suspended soil runoff collected during the sprinkle infiltration test. Soil fertility sampling was completed every fall from 2011 to 2014 and additional sampling of soil physical properties was taken in the spring between 2013 and 2014. Differences between fall conservation tillage treatments, no-till (NT), AerWay® aerator (AA), and Great Plains Turbo-Till® (GP), and topographic positons, concave, convex and linear were analyzed. Sediment runoff and earthworm biomass were also collected in the fall in 2014. Results indicated a significant increase of soil organic matter (12%-24%), water stable aggregates (78%-98%), phosphorus (43%-76%), and cation exchange capacity (28%-35%) within concave over the convex landscape positions. Soil strength was significantly lower in the field managed with the GP vertical tillage disk compared with the AA field to a depth of 27.5 cm and the NT field to depth of 17.5 cm. Crop residue coverage (percent covered) was more complete in the NT field (12%) and the GP field (3%) compared with the AA field. Suspended sediment runoff was negatively correlated with water-stable aggregates, Ca, and Mg, but positively correlated with earthworm biomass. Extractable nutrients and soil physical properties were also strongly affected by air temperature and precipitation throughout the study period. Characterizing soil properties within topographic positions has potential applications in precision agriculture management, such as reducing excessive fertilization, and identifying areas of increased pollution potential. Evaluation of the tandem effects of conservation tillage tools and topographic position within central Illinois is important in order for the optimization of production and conservation of resources. Physical disturbance from tillage and the transport of sediment from eroded areas to depositional topographic positions are key factors influencing the variability of soil properties, crop productivity, and potential sediment-borne nutrient pollution within individual agricultural fields.

MSCAGR (Soil Science) / Department of Soil Science / Soil resilience is the ability of a soil to recover its function or capacity after applied stress such as crusting. Some soils have high potential for recovery while others have poor resilience. Soils with poor resilience are much more vulnerable to degradation. Many soils in South Africa are susceptible to crust formation, which affects many soil surface properties and processes and hence productivity. The objectives of this study were to demonstrate how soil resilience to crust formation is affected by conventional tillage and conservation agriculture in selected soils in South Africa. Soil samples were collected from four different soils (Hutton, Shortland, Glenrosa and Dundee) using PVC pipes with the length of 20 cm and diameter of 5cm and scanned using micro xray computed tomography for total pores. Total porosity from Luvisols, Ferrosols, Leptsols and Fluvisols under both conventional tillage and conservation agriculture was used to find soil resilience index. Soil crusting was influenced by both soil texture and clay mineralogy. The dominance of kaolinitic mineral caused the soil to be more stable as compared to soil dominated by quartz. Luvisols, Ferrosols and Leptsols were more stable and had aggregate stability of 57%, 69,5% and 32,7%, respectively. On the other hand, Fluvisols had poor aggregate stability with the value of 14,2%. Total porosity was in the order of 34,3%>32,2%>23,5%>16,3% for Ferrosols, Luvisols, Leptsols and Fluvisols, respectively. Soil crusting influenced the total porosity. Tillage practices had influence on soil crust formation hence, total porosity of the soils. Total porosity was higher under conservation agriculture as compare to conventional tillage. Resilience total porosity was in the order of 37,5> 23,9> 4,1> -30,1 on Luvisols, Ferrosols, Leptsols and Fluvisols, respectively. Soil resilience to crust formation was influenced by tillage practices. Soil resilience of Luvisols, Ferrosols and Leptsols can be achieved through conservation agriculture however, soil resilience of Fluvisols can be achieved through conventional tillage. / NRF