Project : USDA ARS

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Research Project: Conservation Systems to Improve Production Efficiency, Reduce Risk, and Promote Sustainability

2021 Annual Report

Objectives
1. Determine weed suppression, soil coverage, and agronomic and economic benefits for monoculture and mixed species high-residue cover crops in conservation tillage for diverse crop production systems of the southeastern U.S. 1a. Evaluate monoculture and mixtures of cereal, legume, and selected Brassica cover crop species on weed dynamics in corn, cotton, peanut, and soybean. 1b. Evaluate and develop integrated weed control systems to diminish herbicide resistant and troublesome weed yield loss in cotton. 1c. Evaluate cover crop management across single species and mixtures to compare soil health benefits, while improving biomass production. 2. Integrate new equipment, high residue cover crops, and conservation tillage into cropping systems that foster sustainability and resiliency, increase efficiency, and reduce risk by promoting soil health and yield stability. 2a. Evaluate effects of different planting factors in a no tillage cotton system with a rye cover crop. 2b. Develop a no tillage equipment system compatible with a modular tractor for vegetable production. 2c. Determine the effects of cereal rye seeding rates and timing of termination methods on soybean production in a no tillage conservation system. 2d. Determine cash crop performance across high residue conservation tillage systems and different agronomic management factors. 3. Increase environmental sustainability of pasture and forage-based beef production systems. Research can include, but is not limited to, incorporating broiler litter into pasture-based grazing systems; cropping systems with beef cattle production through grazing cover crops utilized in soil conservation programs; production of forages adapted to local growing conditions and resilient to a changing southern climate to improve production efficiency and environmental benefits; and lowering fertilizer and energy inputs and associated production costs to maximize profitability.

Approach
Research objectives are designed to develop conservation systems that will improve soil quality, conserve natural resources, and increase production efficiency, increase environmental sustainability of pasture and forage-based beef production systems, while reducing risk for producers. These objectives will be accomplished by examining cover crop benefits (agronomic and economic) for single species and mixtures across diverse cropping systems of the southeast. In addition, we will also examine how integrating cover crops with management strategies designed to maximize benefits for cropping systems will promote soil health and productivity. Major areas of focus include: (1) examining weed germination across single species cover crops and mixtures for popular row crops grown across the southeast; (2) integration of cover crop mixtures into herbicide resistant weed control strategies; (3) comparisons of cover crop management strategies across single species cover crops and mixtures to identify how to maximize benefits; (4) evaluation of cover crop seeding rates, termination timing, and cash crop planting speeds on cash crop productivity; (5) development of equipment for a modular tractor suitable for vegetable production; (6) evaluation of cash crop performance across high residue cover crop systems; and (7) identifying tillage and seeding rate guidelines for a carinata biofuel crop. In addition, the research will focus on incorporating broiler litter into pasture-based grazing systems; cropping systems with beef cattle production through grazing cover crops utilized in soil conservation programs; production of forages adapted to local growing conditions and resilient to a changing southern climate to improve production efficiency and environmental benefits; and lowering fertilizer and energy inputs and associated production costs to maximize profitability.

Progress Report
Experiments and data analysis have been accomplished or is on-going for multiple experiments designed to examine how cover crop management affects cover crop benefits. This includes experiments and data analysis for comparisons between single species and multi-species cover crops for soil C level, microbial activity, and weed suppression across various cropping systems. Studies designed to examine how cover crop management affects cash crop benefits are continuing. Research was concluded for carinata, a potential biofuel crop for the Southeast, that involves investigating interactions between carinata seeding rates within conventional and conservation tillage systems. Other research included examining different forms of surface tillage across different N rates for winter wheat production. Cooperative research with Auburn University to examine how single and multi-species cover crops affect soil properties is also continuing, as well as determining how cover crop grazing duration affects soil and crop productivity. In addition, experiments evaluating machinery designed for cover crop termination and subsequent design refinement continued. Technology transfer activities related to many facets of all the previously described research were also conducted.

Accomplishments
1. Conservation tillage cotton would benefit from broadcast soil-applied herbicide applications when infested with palmer amaranth. Conservation tillage adoption continues to be threatened by glyphosate and acetolactate synthase–resistant Palmer amaranth and other troublesome weeds. An ARS researcher in Auburn, Alabama, conducted experiments to evaluate the effect of a cereal rye cover crop using high- or low-biomass residue, followed by wide or narrow within-row strip tillage and three PRE herbicide regimens on weed control and seed cotton yield in glyphosate-resistant cotton. In most comparisons, surface disturbance width, residue amount, and soil-applied herbicide placement did not influence within-row weed control; however, broadcast PRE resulted in increased carpetweed, large crabgrass, palmer amaranth, tall morning-glory, and yellow nutsedge weed control in row middles compared with plots receiving banded PRE. In addition, high-residue plots had increased carpetweed, common purslane, large crabgrass, Palmer amaranth, sicklepod, and tall morning-glory weed control between rows. These results will be used in guidelines for weed management and subsequent retention of conservation systems throughout the U.S. cotton belt.

2. Production management information that included conventional tillage systems was developed for carinata. Production management information that included conventional tillage systems was developed for Carinata, a potential biofuel crop, that can be grown during the winter when cash crops are not traditionally grown in the the Southeast. Understanding carinata performance across conservation tillage systems benefits growers interested in maintaining soil health and lowering production costs. An ARS researcher in Auburn, Alabama, along with University of Florida researchers examined different combinations of carinata seeding rates and tillage methods to optimize yield across southern Alabama and northern Florida. Regardless of tillage method, a seeding rate of 5.6 kg/ha was best. These updated seeding rates and general agronomic guidelines to improve yield for a winter crop grown during a season not traditionally used by growers, and would likely result in extensive farm revenue generation.

3. Management of high-residue cover crops in an organic farm production is possible. Cover crops have been shown to reduce soil erosion, improve soil quality, reduce energy costs, and promote farm profitability, however, organic row crop and specialty crop producers struggle to terminate winter cover crops without herbicides. Experiments conducted by an ARS researcher in Auburn, Alabama, evaluated newly developed roller/crimper equipment to terminate cover crops with four different termination-timing practices with different types of cover crop species. Commercially available vinegar and cinnamon/clove oil solutions provided little predictable termination, and producers attempting to use these OMRI-approved products will likely resort to cover crop incorporation, or mowing, to terminate covers if no other practice is readily available, thus negating potential cover crop benefits. Cover crop termination using the roller/crimper technology during March or later was also found to be ineffective, however, termination was found to be successful for this technology when used in April or May. The roller/crimper technology was found to be effective for all winter cover species when followed by a broadcast flamer and for hairy vetch, winter peas, and cereal rye when utilizing clear plastic for the cash crop. These results will be utilized to update organic conservation agriculture high residue cover crop termination guidelines and will likely result in increased conservation systems adoption.

4. Best management practice for organic kale and cereal rye grain production following a sunn hemp cover crop were developed. Experiments were conducted by an ARS researcher in Auburn, Alabama, to determine how three sunn hemp cover crop termination methods (rolling, mowing, and mowing with incorporation) affected organic kale and cereal rye for grain production. Greater kale yields were obtained following mowed and incorporated residue compared to mowed and rolled sunn hemp. These lower yields were related to poor kale seed-to-soil contact (hair pinning) due to the extremely high sunn hemp biomass on the soil surface. Similarly, cereal rye grain yield had higher yields observed following rolled and mowed residue and mowed and incorporated residue. Better soil planting conditions following rolling and mowing sunn hemp resulted in higher yield of cereal rye grain. In addition, higher levels of nitrate and ammonium in the topsoil were measured at planting for each cash crop compared to levels at sunn hemp termination, indicating N release from sunn hemp residue. Overall, findings from this study will be used to update guidelines for selecting a suitable cover crop combined with proper management of the residue to optimize crop yields in organic vegetable conservation systems.

5. Equipment developed for small and urban conservation farming systems. Small/urban farms are increasing in number due to consumer demands for locally grown produce. These farms often use small walk-behind tractors. However, lack of specialized equipment that can be used with walk behind tractors inhibits widespread adoption of conservation system. To enable adoption, no-till equipment has been designed, fabricated, and tested in a field experiment by an ARS researcher in Auburn, Alabama. Prototypes of a no-till seed drill, a roller/crimper, and a no-till vegetable transplanter were utilized to plant tomatoes. Results showed optimum rye seed germination (95% rye termination three weeks after rolling without herbicide), a uniform tomato plant spacing (less than 10% of spacing variation) and a commercially acceptable tomato yield could be achieved using this equipment. These results will advance conservation vegetable production system adoption in small farms globally, and especially relatively small U.S. organic farms.

6. Influence of rolling/crimping for cover crop termination on soil strength and yield in no-till cotton was examined. Field experiments were conducted by an ARS researcher in Auburn, Alabama to evaluate effects of multiple rolling/crimping operations utilizing different types of experimental rollers (developed at the National Soil Dynamics laboratory) on cereal rye cover crop termination, soil compaction, and seed cotton yield in a conservation system. Results indicated that one week after rolling cereal rye 3 times, the improved 4-stage and 2-stage rollers, had termination rates above 90%, which were similar to a widely utilized glyphosate herbicide application. Overall, rolling cereal rye cover crop 2 or 3 times did not cause soil compaction, and soil strength at 0-15 cm depth following rolling did not exceed the 2.0 MPa limit for unrestricted root growth. In addition, seed cotton yield was not affected by rolling 2 or 3 times, indicating that multiple rolling did not influence yield. These results will be used in guidelines for cover crop production and subsequent adoption/retention of conservation systems throughout the U.S. cotton belt.

7. Cover crop biomass is unaffected by common herbicide soil residuals. Cover crops can provide many benefits to peanut and cotton crops planted in rotation including suppressing weeds, conserving soil moisture after termination, increasing soil organic matter, and reducing soil erosion. However, herbicide carryover can affect cover crop establishment. An ARS researcher in Auburn, Alabama, collaborating with Auburn University researchers investigated the responses of six cover crops to twelve soil residual herbicides in a multi-location experiment. Oat showed the most tolerance with no treatments reducing any growth parameters. Although stand reduction, initial injury, and stunting may occur in cover crop species, biomass at termination was not affected by herbicide residues evaluated in this study. These results will be used in guidelines utilized by conservation agriculture systems producers throughout the Southeastern U.S. and will result in increased conservation systems adoption and retention.

U.S. DEPARTMENT OF AGRICULTURE

Soil Dynamics Research: Auburn, AL