Location: Crop Production Systems Research
2020 Annual Report
Objectives
Objective 1. Evaluate different cover crop species, tillage practices, and management strategies for increasing soil health and crop productivity.
Sub-objective 1A. Determine the effects of different cover crop combinations on soil health and crop yield in corn production systems.
Sub-objective 1B. Assess the long-term impact of crop rotation, cover crop, and no till practices on soil health.
Objective 2. Determine the impact of 2,4-D on soil health in corn, cotton, and soybean production systems.
Sub-objective 2A. Assess the potential impacts of 2,4-D+glyphosate application on biological parameters in bulk soil.
Sub-objective 2B. Evaluate the efects of 2,4-D+glyphosate application on soil biological parameters in corn, cotton, and soybean systems.
Approach
Agricultural management practices, such as tillage and herbicide application, can have detrimental effects on soil quality that may ultimately impose limitations on sustained crop production. As such, better management practices are needed in modern cropping systems that promote soil health while sustaining optimum crop yields. Cover crops have gained increased attention as a way to promote soil heath and water quality through reduced soil erosion, improved soil tilth and organic matter, and enhanced activity of microbial communities in soil. Cover crop use in the Mid-South United States has been limited, but farmers in the region are beginning to show an interest in incorporating them as a management practice to improve soil health and ensure sustainable production. Proposed research will evaluate how different types of cover crops impact key aspects of soil health and row crop yields, including corn, cotton, and sorghum. With this knowledge, recommendations can be made to farmers on what cover crop combinations are best for improving soil health while optimizing crop production in the Mid-South region. Agricultural systems also face the challenge of controlling glyphosate resistant weed populations. New cropping systems tolerant to both glyphosate and 2,4- dichlorophenoxyacetic acid (2,4-D) are being introduced as a way to combat glyphosate- resistant weeds. However, herbicides have the potential to inhibit microbial populations, and there is limited information available on how 2,4-D might impact soil health. Thus, this research will examine impacts of 2,4-D+glyphosate on soil health in cotton, corn and soybean systems under field conditions. This project will result in guidelines for practices that ensure long-term sustainability of soil health while maintaining optimal crop production.
Progress Report
Under Subobjective 1A, a cover crop study examining the effects of different numbers and combinations of cover crops on soil health was initiated in November of 2019, with the planting of all different combinations of three cover crops (crimson clover, rye, and hairy vetch). Cover crops were allowed to grow over the winter and terminated in late spring. The summer crop of corn was planted in May 2020. Baseline samples in the fall, as well as spring and early summer soil samples have been collected. Mid-summer and fall samplings are planned, provided weather and work-site conditions are favorable. Fall samples were sieved, analyzed for pH, moisture content, soil organic matter, and extracellular enzyme activities (phosphatase, beta-glucosidase, N-acetylglucosamindase, cellobiohydrolase, and fluorescein diacetate hydrolysis), as well as processed by chloroform fumigation and extraction for the determination of microbial biomass. Processing of spring and summer samples has been slowed due to a large backlog of samples. Extracellular enzyme assays on spring samples has been completed, and processing of summer samples is in progress. All other analyses have been postponed. For the second year of the LTAR study under Subobjective 1B, cover crops were planted in the fall and cotton and sorghum planted in the spring by collaborators on the study, but spring soil sample collection was missed due to a combination of weather conditions, work restrictions, and scheduling conflicts with sample collection for other studies. Mid-summer and fall sample collection are planned, provided weather and work-site conditions are favorable.
Under Subjective 2A, a three-month lab incubation experiment on the effects of different combinations of 2,4-dichlorophenoxyacetic acid (2,4-D) and glyphosate application on bulk soil was started in early February. Samples were analyzed for soil extracellular enzymes for all time points, but soil moisture and pH determinations for the day 60 and day 90 time points, as well as extractions for soil microbial biomass for the day 90 timepoint, have been postponed. Under subobjective 2B, corn was planted and baseline samples were collected in early April for the second year of the study examining the effects of 2,4-D+glyphosate application on the microbial communities in bulk and rhizosphere soil of resistant corn plants under field conditions. However, only one herbicide treatment was made and rhizosphere analysis could not be carried out. An attempt was made to initiate the first year of a field study examining the effects of 2,4-D + glyphosate on soil resistant soybean systems. The soybean for this experiment was planted and baseline samples were collected in early May, but herbicide treatment and post-herbicide analyses could not be made. Both field studies will need to be repeated next year.
Accomplishments
