Improving soil health in agricultural soils is vital as the effects of climate change and an increasingly affluent population are putting a strain on land resources. Conservation agricultural practices such as cover cropping and conservation tillage systems (e.g., strip tillage, minimal tillage, or no tillage) are implemented to improve soil properties, but soil health outcomes in Coastal Plain cropping systems have been inconsistent and may take decades or longer to occur. Improving soil health and agricultural prosperity in the region requires: a better understanding of the rate and magnitude of response in soil properties to different types of management; and a better understanding of the interaction between management types, soil health parameters, and crop yield. In this study, four tillage systems (in order of decreasing intensity: conventional tillage > strip tillage > minimal tillage > and no tillage) and three winter cover rotations (in order of decreasing expected biomass input: high-biomass cover crop > winter cash crop > and fallow) were tested in a split plot design. For the first objective of this study, bulk density, penetration resistance (as depth to root restrictive layer), total organic carbon, carbon stocks, saturated hydraulic conductivity, and yield were measured repeatedly over a seven-year period to better understand the longitudinal response of these properties to management. Bulk density and saturated hydraulic conductivity showed a greater temporal variation in the more intensive tillage practices (strip tillage and conventional tillage) in the top 5 cm. Depth to root restrictive layer was consistently highest in the deep tillage treatments (strip tillage and minimal tillage). The change in soil organic carbon concentration between 2018 and 2022 in the top 5 cm was numerically greater in the strip tillage (0.67%) and no tillage (0.68) than the conventional tillage was 0.18%. In 2022, the carbon stocks were significantly increased in all three conservation tillage treatments compared to conventional tillage. Yield was significantly increased by winter cover in the years that a legume/non-legume cover crop mix was implemented. For the second objective of this study, the effects of 6 years of management were evaluated for total organic carbon, active carbon, short-term carbon mineralization, aggregate stability, and crop yield. These parameters were then correlated to determine drivers in soil health outcomes. Total organic carbon was increased in the strip tillage treatment (1.13% in 2021 and 1.61 % in 2022) compared to conventional tillage (0.83% in 2021 and 1.09% in 2022) in the top 5 cm. In 2022, total organic carbon under cover crop (1.51 %) and cash crop (1.46 %) treatments were also significantly higher than the fallow (1.33 %) in the top 5 cm. Active carbon results followed a similar but weaker trend in both years. Percent aggregate stability was improved by minimal tillage (47%) in 2022 compared to conventional tillage (41%). The findings from the correlation analyses suggest that total organic carbon concentration, soil texture, and tillage were all prominent drivers in improving soil health outcomes. These results demonstrate the relatively slow response of many soil physical properties to management, highlight the need for consistent management to improve properties, and emphasize the need to take measurements at different times of the year. This information can be used to develop more sustainable and resilient cropping systems in the Coastal Plain. / M.S. / Centuries of intensive farming practices have degraded agricultural soils, which contributes to the challenge of feeding a growing and increasingly affluent global population. Therefore, understanding which farming practices reverse this degradation and improve soil health is vital for regions such as the southeastern Coastal Plain, where agriculture is a prominent industry. Soil health is defined as the ability of soil to support life sustainably. Conservation agricultural practices, such as planting crops over the winter and conservation tillage systems (where at least 30% of the soil surface is left undisturbed) are implemented to improve soil properties, but soil health outcomes in Coastal Plain farms have been inconsistent and may take decades or longer to occur. Therefore, the improvement of environmental health and agricultural prosperity in this region requires a better understanding of the patterns of change in soil properties in response to different types of management; and a better understanding of the factors that most influence soil health outcomes. This study evaluated the combination of four tillage systems of differing intensities, and three winter crop types on soil health outcomes. For the first objective of this study, soil physical properties, soil carbon, and crop yield were measured repeatedly over a seven-year period to quantify how these properties respond to management. The soil physical properties showed temporary improvement by more intensive tillage but reverted in the months after tillage. The soil carbon increased from 2018 to 2022 in the three least-intensive tillage treatments. Crop yield was significantly increased in years when there was a mix of crop species planted. For the second objective of this study, the effects of management on soil carbon, soil stability, and crop yield were evaluated after six years of management. These soil health parameters were then correlated to determine the most prominent factors influencing change in soil properties. Soil carbon and soil stability were both improved in least-intensive tillage treatments. The findings from the correlation analyses suggest that soil carbon concentration, soil texture, and tillage were all prominent factors in improving soil health outcomes. These results demonstrate the relatively slow response in many soil physical properties to management, highlight the need for consistent management to improve soil health, and emphasize the importance of taking measurements at different times throughout the year. Furthermore, this is information that can be used to develop more sustainable and resilient cropping systems in the Coastal Plain.

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Master of Science / Department of Biological and Agricultural Engineering / Philip L. Barnes / The world’s population has passed 7 billion and is expected grow to more alarming numbers by the year 2050. The increase in human life on the planet ushers the need to responsibly and sustainably grow more food. In order to meet the demand necessary, it is crucial that soil remains healthy and crop yields continue to increase in efficiency. Irresponsible or ill-informed practices can lead to depleted resources and degradation of fertile soils that may limit a producers’ ability to sustainably grow food. Cover crops are a tool that can be used to address issues the modern producer may face. Cover crops have been shown to increase cash crop productivity, improve soil health by improving soil physical and chemical properties as well as providing protection from soil erosion runoff or nutrient leaching. A study was conducted in 2014 to examine the short term effects associated with cover cropping systems. The effects of ryegrass, red clover and a cover crop cocktail (mixture of ryegrass, red clover and hairy vetch) compared to bare tilled and bare control plots were studied. The five treatments were replicated three times in a completely randomized study and analyzed. Soil physical health indicators such as bulk density and porosity were calculated. Soil and cover crop nutrient use, as well as, soil moisture content data was collected and analyzed using excel and ANOVA statistical procedures. In the short term, the study found that there was only statistically significant differences between cover cropping regimens, tilled and control plots in regards to biomass production and biomass nutrient concentrations (α=0.05). The cocktail mix provided more biomass, N and P than the ryegrass and clover plots alone. Observable differences in cover crop volumetric soil moisture and water used between plots demonstrated that cover crops utilize soil moisture in the short term, which must be considered in areas experiencing water stress. Although more long-term data is needed to truly quantify how cover crops effect various aspects of soil health, this study demonstrated how cover crops have the potential for providing numerous benefits such as increased erosion control, lower reliance on anthropogenically created nutrients and the reduction of weeds. Overall the benefits associated with cover crops are still being researched and while adoption of cover cropping systems has been slow, a push towards agricultural sustainability while increasing food production will increase the amount of producers utilizing cover crops in the coming years.

<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>

Protection of water resources in a changing climate depends on bottom-up stewardship and adaptive management. From the ground up, a vital component is maintaining soil ecosystem services that regulate water, recycle nutrients, sequester carbon, provide food, and other benefits. Interacting spatial, social, and physical factors determine agricultural and stormwater management, and their impact on water. This dissertation explores these dimensions within a complex social-ecological system. The first chapter evaluates a participatory process to elicit solutions to complex environmental problems across science, policy, and practice. The second chapter studies on-farm soil assessment and its role in informing management decisions and supporting adaptive capacity. The third chapter investigates cross-scale dynamics of residential green stormwater infrastructure (GSI) for improved water resource management in a broader social-ecological context. Integrating participant feedback into current science, research, and decision-making processes is an important challenge. A novel approach that combines a Delphi method with contemporary “crowdsourcing” to address water pollution in Lake Champlain Basin in the context of climate change is presented. Fifty-three participants proposed and commented on adaptive solutions in an online Delphi that occurred over a six-week period during the Spring of 2014. In a follow-up Multi-Stakeholder workshop, thirty-eight stakeholders participated in refining and synthesizing the forum’s results. The stakeholders’ interventions from the crowdsourcing forum have contributed to the current policy dialogue in Vermont to address phosphorus loading to Lake Champlain. This stakeholder approach strengthens traditional modeling scenario development to include priorities that have been collectively refined and vetted. Healthy agricultural soils cannot easily be prescribed to farms and require knowledge and a long-term commitment to a holistic and adaptive approach. The second chapter addresses the questions: “to what extent do farmers use indicators of soil health, and does feedback inform management decisions?” A survey of farmers in two Vermont watersheds was conducted in 2016 showed relatively high use of fourteen soil indicators and high rankings of their importance. The finding that there were differences in use and perceived importance of soil indicators across management and land-use types has implications beyond the farm scale for agriculture, and the provision of ecosystem services. Soil management relates to broader adaptation strategies including resistance, resilience, and transformation that affects adaptive capacity of agroecosystems. Bottom-up adoption of environmental behaviors, such as implementing residential GSI, need to be understood in the context of the broader social-ecological landscape to understand implications for improved water management. A statewide survey of Vermont residents paired a cross-scale and spatial analysis to evaluate how intention to adopt three different GSI practices (infiltration trenches, diversion of roof runoff, and rain gardens) varies with barriers to adoption and household attributes across varying stormwater contexts from the household to watershed scale. Improved stormwater management outcomes at the watershed and local levels depend on management strategies that can be implemented and adapted along the rural-urban gradient, across the bio-physical landscape, and according to varying norms and institutional arrangements.

Shelterbelts were established in the Canadian Prairies as a means to protect soil from wind erosion. Knowledge gaps remain about shelterbelts' ecosystem services to the agro-landscape, hence hiding farmers' trade-offs in a changing agriculture. This research first investigated shelterbelts' effect on soil biological activity and fertility. Soil samples were collected in September 2012 from sheltered and non-sheltered fields in the Rural Municipality of Stanley, Manitoba. Results showed that shelterbelts promote higher soil biological activity, potentially correlated to the enhanced organic matter and micro-climate adjacent to shelterbelts. A survey was then conducted to explore shelterbelts' cultural services to the local community. Results indicated that while shelterbelts were perceived to significantly benefit community well-being, they were mainly recognised for agricultural functions. We conclude that shelterbelts are a significant element of both supporting and cultural ecosystem services, contributing to the prairie agro-system resilience. Further research and quantification of shelterbelts' socio-ecological services is recommended.

Master of Science / Department of Agronomy / Charles W. Rice / Declining soil health is the underlying cause of decreasing agricultural productivity and environmental degradation. To address this challenge, research was conducted to determine how: (1) cover crops affect soil health in Kansas, USA and (2) direct seeding mulch–based cropping (DMC) systems affect soil health in Nyankpala, Ghana. Soil health indicators assessed include: biomass yield (kg ha[superscript]-1), soil microbial respiration (SMR), soil microbial C and N (MBC & MBN), potentially mineralizable N (PMN), dissolved organic carbon (DOC), soil organic C (SOC), soil total nitrogen (TN), phospholipid fatty acid analysis (PLFA), water stable aggregate (WSA), bulk density, pH, N, P, K, Ca and Mg. DMC systems from Ghana yielded significantly greater biomass compared to the control. High biomass produced by DMC systems did not increase SOC and PMN relative to the control. Fertilizer application had a significant impact on biomass production, which resulted in a significant increase in SOC and PMN in the 0-5 cm soil layer. Soil pH was significantly reduced by cropping systems and fertilizer in the 0-5 cm soil layer. Microbial biomass N, TN, SMR, N, P, Ca and Mg were not affected by the DMC cropping systems. Application of mineral fertilizer increased SMR, MBN, TN, N, and P. Soil K was also significantly affected by cropping systems and mineral fertilizer. The combination of mineral fertilizer and plant residues would be needed to improve soil health and increase crop productivity in the Guinea Savanna Zone of Ghana. Liming would be required to address low soil pH. In the USA, of all the soil health indicators examined, actinomycetes, gram-positive bacteria, fungi-bacteria ratio (F:B), SMR, MBN and WSA, were those significantly influenced by cover crops. The interactive effect of cover cops and N fertilizer also affected gram-positive bacteria, total PLFA, MBN, F:B ratio and WSA. Cover crop residues contributed to the observed differences in these indicators. The low response of soil health indicators suggest further evaluations are needed to determine the effectiveness of the indicators.

Master of Science / Department of Agronomy / DeAnn R. Presley / Cover crops have numerous benefits and while cover crops have been used for centuries, currently there are few producers in Kansas growing them and so there is a need for additional research on how cover crops affect soil properties, and on the potential for utilizing cover crops as forage. Two studies are presented in this thesis. The first study evaluated the use of cover crops in a vegetable production system as compared to a fully tilled control. This study evaluated soil physical properties in the form of wet aggregate stability and infiltration, and microbial properties by soil microbial biomass carbon (MBC). Over the three year study, the most pronounced differences observed were in the wet aggregate stability between the cover crop and control treatments where the cover crop treatments had better soil aggregation compared to the control. At the conclusion of the study, there was not a difference between fall and spring planted cover crop treatments. The second study evaluates species composition and forage quality of various combinations of multi-species cover crop mixtures. This study evaluated sixteen treatments, each consisting of a three-way mixture of a brassica (turnip or radish), grass (rye, wheat, barley, oat), and a legume (berseem clover or Austrian winter pea). Species composition analysis found that the brassica species dominated the mixtures (60-80% by mass on a dry weight basis) in 2014 while the grass species were dominant (62 – 67%) in 2015. Overall all treatments produced prime quality forage (as compared to hay values), however some treatments cost significantly more to plant than others. Therefore an economic analysis compared the treatments and found that the treatments containing turnips and oats generally provided the best return on investment given that both of these species were among the cheapest to plant and produced moderate to high biomass compared to the other treatments. The results of these projects point to the potential benefits that cover crops can have for producers interested in improving soil or utilizing cover crops for forage.

Retention of a sugarcane mulch blanket, following green cane harvesting could increase soil water conservation, soil health (organic matter content and micro-organism activity) and soil nutrient status. However, little is known about the effect of such a mulch layer on sugarcane crop growth and development. To study the latter, an experiment was carried out in Komatipoort at the South African Sugarcane Research Institute’s Experimental Station. Row spacing arrangement was either 1.5 m or 1.2 m x 0.6 m tram rows. N14 was planted as a fast canopy growing cultivar and N26 as a slow canopy growing cultivar. Plots were either covered by a mulch layer or left as bare soil. Stalk population, stalk height and radiation interception were measured every second week. Soil temperature readings were logged hourly at a depth of 0.15 m. Preliminary results indicated that early growth and development of sugarcane was delayed under mulch treatments. Stalk length of N26 was reduced more than that of N14. Stalk population of both cultivars were significantly lower under the mulch treatment. Fractional interception of solar radiation was only 50% at 150 days after planting for the mulch treatment, compared to 70% for bare plots. Slow initial growth and delayed canopy development in mulch treatments were associated with low soil temperatures in the period leading up to full canopy closure. Soil temperature in the mulch treatments remained between 3 to 4oC lower than the bare soil treatments. Early indications are that the presence of a mulch layer may reduce early growth and development of sugarcane. Copyright / Dissertation (MInstAgrar)--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

Organic labeling organizations like KRAV have an important role to play in affecting consumer purchasing decisions as well as producer crop cultivation behaviours. With soil health becoming an ever increasing concern, and soil so central to the catalysing cycles of carbon, nutrients, and energy in the ecosphere, sustainable development could benefit from understanding better the relationship of organic labelling organizations to soil. This thesis explores that relationship through a review of relevant literature including the guidelines for KRAV certification 2019-2020, as well as interviews with former KRAV employees and a current KRAV certified farmer. Therewith, this research investigates this complex interplay of relevant actors - consumer, farmer, certification body, and standard holder- to elucidate KRAV’s approach to soil health. Whereas some environmentalists might argue for stricter guidelines and more holistic testing, the participants in this study presented a firm case for the difficulty of implementing further soil testing. This study is best understood to be an initial and exploratory investigation into a topic that requires more attention to draw firm conclusions from in the future. In future studies, it may be beneficial to cross-compare practices and mentalities of people involved in organic certified production from different labels.