Location: Crop Production Systems Research
2024 Annual Report
Objectives
1. Determine optimal soil amendments in row crop fields for minimizing potential for off-target agrochemical release into downstream ecosystems.
1.A. Relate cover crop, gypsum, and biochar-induced changes in soil physical, chemical, and biological properties to the potential for the release of herbicides from soils.
1.B. Evaluate the impact of multi-species cover crop mixes of legumes, cereals, and legumes + cereals on soil biogeochemistry parameters and potential for off-target herbicide transport.
2. Identify conservation management practices that enhance ecosystem services within row crop fields in the Mississippi Delta and improve resilience to weather extremes.
2.A. Evaluate the effects of winter cover crop complexity on plant growth promoting endophytic communities in corn during the summer growing season.
2.B. Determine if changes in soil physical, biological, and chemical parameters resulting from conservation management practices impact pollinator resources in corn and cotton production systems.
2.C. Determine the effects of no-till and cover cropping on soil water storage in response to episodes of drought in cotton production systems.
Approach
Agricultural production of row crops can have deleterious effects on soil health and downstream ecosystems, ranging from depletion of soil organic matter and nutrients to increased erosion and transport of agrochemicals into downstream ecosystems. A variety of conservation and soil management practices have been put forth as options to ameliorate some of these negative effects, including no-till management, winter cover crops, and soil amendments such as biochar. However, these practices incur added costs to farmers. As such, there has been increased interest in determining how these practices can improve ecosystem services in order to maximize the benefits received from their implementation. The proposed research will evaluate how soil health improvements seen in response to these management practices contribute to a variety of these different services. There are key aspects within management and cropping systems that need additional attention to fully understand the nature of soil health’s effects on ecosystem services. Specifically, this research will address the impacts on: pesticide fate and transport; the performance of beneficial endophytic microorganisms; and the contributions of different management practices and cropping systems to the performance of pollinators and pollinator resources. Pesticide sorption/desorption in soil from cover crop and soil amendment plots will be assessed to determine which management practices are best at limiting the potential for off-target herbicide transport, and herbicide concentration at key drainage sites will also be assessed and compared to prevailing land management practices in the surrounding areas. The endophytic community composition in corn grown under different cover crop mixtures will be analyzed to determine if cover crop selection can be used to recruit and promote colonization of plant tissue with endophytic microorganisms involved in plant growth promotion and biocontrol of disease. In addition, pollen and nectar samples from various cover crop and summer crop species will be analyzed to determine the effects of tillage and winter cover cropping on nutrient quality in pollinator resources. The results of this research will provide valuable insight into the selection of cover crop and soil amendments to maximize ecosystem benefits while maintaining optimum crop productivity.
Progress Report
This report documents progress on the first five months of new project, which was approved in April 2024 and continues research from project 6066-12220-006-000D, "Assessment and Improvement of Soil Health Under Modern Cropping Systems in the Mid-Southern United States", which terminated in August 2023. This report also covers work done under bridging project 6066-12220-007-000D, which covered the gap in time between old project termination and new project approval.
Under Sub-objective 1A, a field study was initiated at a small plot research farm in Stoneville, Mississippi, to determine if cover crops and soil amendments can impact the loss of herbicides from soil in corn and soybean fields. Cover crop treatments of winter pea (for corn) and winter wheat (for soybean) were planted in the fall of 2023, allowed to grow during the winter, and terminated in the spring of 2024. Soil amendment treatments of biochar and gypsum were applied during the winter fallow period. For Sub-objective 1B, a study was prepared to evaluate how different cover crop mixtures impact soil health (ability to support crop growth and function as part of the ecosystem) and off-site herbicide transport. The treatments included a three-species legume mix, a three-species grass mix, and an eight-species legume-grass mix. These cover crops were planted in the fall, allowed to grow during the winter, and terminated in the spring. For the studies under both Sub-objective 1A and 1B, corn and soybean were planted in the spring after cover crop termination. The above ground cover crop biomass was collected prior to termination, and the dry weight has been determined. Soil samples were collected in the fall before cover crop planting or biochar and gypsum application, as well as in the spring before cover crop termination. These samples are being analyzed to determine how each treatment impacted soil health. In June 2024, an experiment was conducted to determine rates of glyphosate dissipation in each treatment. Glyphosate was applied to the field plots, and soil samples were collected at 1, 7, 14, and 28 days after application. These samples will be analyzed for glyphosate concentration to determine decreases in glyphosate over time compared to the amount of glyphosate applied to the soil. Soil samples have been analyzed for soil moisture and some chemical parameters. Analyses of glyphosate and the remaining chemical, physical, and biological soil parameters are pending.
Under Sub-objective 2A, the first year of a study on how different winter cover crop combinations affect the endophytic bacterial community (bacteria that live within plant tissue without causing disease) in corn was started at the experimental research farm in Stoneville, Mississippi. Cover crop treatments included all combinations of three cover crops (crimson clover, rye, and hairy vetch). Cover crops were planted in the fall of 2023, allowed to grow over the winter, and terminated in the spring of 2024. The above ground cover crop biomass was collected prior to termination, and the dry weight has been determined. The summer crop of corn was planted in May 2024. Root and leaf tissue were collected from corn plants in June and July, which corresponded with important stages of corn development. These samples were processed to remove bacteria on the plant surface, and frozen to preserve the tissue to analyze the endophytic bacterial community inside the plants. Soil samples were collected in the fall before cover crop planting, in the spring before cover crop termination, and the week after corn tissue was collected for endophyte analysis. Soil enzyme activities, moisture content, and organic matter have been determined for spring soil samples, while summer soil samples are currently being processed. Nutrient and biological measurements on soil samples are pending. Portions of all soil samples have been frozen to preserve them for later analysis of the microbial community. For Sub-objective 2B, when the corn reaches the tasseling stage, soil, root, and leaf tissue will be collected again, along with pollen. These samples will be analyzed to determine if the changes in soil health induced by winter cover crop treatments influence the nutrient levels in corn pollen. For Sub-Objective 2C, cotton has been planted in a previously established long-term no-till site in Stoneville to prepare for a new study looking at the effects of tillage and cover crops on soil water storage in cotton during drought. Baseline soil samples have been collected, and analyses of basic soil health measurements are pending.
Accomplishments
Review Publications
Mubvumba, P., Tyler, H.L. 2024. Evaluation of single and mixed cover crops species, in the Mid-South USA. Agronomy Journal. 116(4):1655-1669. https://doi.org/10.1002/agj2.21574.
Mubvumba, P., Delaune, P.B., Hons, F.M. 2023. Cover crops impact to carbon-nitrogen cycling and wheat yields. Soil & Tillage Research. 13:2023. https://doi.org/10.1016/j.soisec.2023.100107.