Location: Soil Dynamics Research
2019 Annual Report
Objectives
Objective 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.
Sub-objective 1a. Evaluate monoculture and mixtures of cereal, legume, and selected Brassica cover crop species on weed dynamics in corn, cotton, peanut, and soybean.
Sub-objective 1b. Evaluate and develop integrated weed control systems to diminish
herbicide resistant and troublesome weed yield loss in cotton.
Sub-objective 1c. Evaluate cover crop management across single species and mixtures to compare soil health benefits, while improving biomass production.
Objective 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.
Sub-objective 2a. Evaluate effects of different planting factors in a no tillage
cotton system with a rye cover crop.
Sub-objective 2b. Develop a no tillage equipment system compatible with a modular
tractor for vegetable production.
Sub-objective 2c. Determine the effects of cereal rye seeding rates and timing of
termination methods on soybean production in a no tillage conservation system.
Sub-objective 2d. Determine cash crop performance across high residue conservation tillage systems and different agronomic management factors.
Approach
Research objectives are designed to develop conservation systems that will improve soil quality, conserve natural resources, and increase production efficiency, 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.
Progress Report
Substantial progress has been made to improve production efficiency, reduce risk, and promote sustainability. Specifically, our research objectives are designed to develop conservation systems that will improve soil quality, conserve natural resources, and increase production efficiency, while reducing risk for producers. Systems are being developed that will benefit producers directly through equipment advances for large- and small-scale producers, management techniques to maximize cover crop benefits associated with soil health, and integration of conservation tillage and cover crop systems. This progress report summarizes the first year of our project plan, but initial activities are discussed below.
Projects have been established and numerous initial observations have been collected for multiple ongoing experiments evaluating high residue cover crop impacts on weed management in corn, cotton, and soybean. Integrated weed control strategies that include cover crops and residual herbicides are increasingly promoted by Natural Resource Conservation Service (NRCS) and cooperative extension systems across the Southeast and Mid-south to help control problematic and resistant weeds without the need for intensive tillage, which is a detriment to soil quality. These experiments are also designed to help develop recommendations for producers facing challenges in conservation systems with regards to troublesome weed control, resistant weed management, and production practices.
Adoption of cover crops on small farms producing healthy foods for local markets is on the rise. To address needs associated with cover crop management on these farms, a two-stage roller crimper and transplanter was designed. The fabrication process is partially completed to begin field testing. In addition, planter studies are on-going to evaluate how planter performance speed with different cotton seeding rates affect cotton yield, and cover crop seeding rates affect soybean yields across different cover crop termination timings.
Studies designed to examine how cover crop management affects benefits, such as soil C and microbial activity, from single cover crops and mixtures are on-going. Tillage comparisons that include different forms of surface tillage are being examined across different Nitrogen (N) rates for winter wheat production. Other on-going tillage work includes an examination of tillage systems and seeding rate interactions for carinata, a potential biofuel crop for the Southeast. Technology transfer activities have continued, which are related to many facets of all the previously described research. Activities include grower meetings, field days, scientific meetings, and factsheets available as handouts or accessed through the ARS website.
Accomplishments
1. Innovative method for cover crop termination using engine exhaust heat. Heat has been used in agriculture in the form of an open flame to control weeds. However, these systems require an additional fuel source. Researchers in Auburn, Alabama, focused on utilizing wasted exhaust heat to terminate cover crops and control weeds in conservation systems. To evaluate this concept at a small farm scale, a mechanical pusher using exhaust heat from the internal combustion gasoline engine with supplemental heat from heater strips was developed to terminate cover crops. The prototype was developed for a walk-behind tractor powered by a single cylinder gasoline engine. Heat to damage plant tissue was directed from the exhaust manifold to a rectangular perforated delivery steel tube that was in continuous contact with the cover crop that had been flattened by the pusher. In addition, a generator powered by the tractor’s Power Take-Off (PTO) provided electrical energy for three parallel supplemental heater strips. Results demonstrated that using exhaust heat (otherwise lost to the environment) is a viable option to terminate cover crops.
2. Specialty crops grown in weed suppressive cover crop residue. Specialty crops historically have been grown in high intensity conventional tillage systems. High residue cover crop systems integrated with traditional vegetable production practices likely offer solutions to some weed management challenges in conservation tillage specialty crop systems. In this experiment by ARS scientist in Auburn, Alabama, watermelon were grown integrating minimal herbicide input, a high residue cover crop and polyethylene mulch, compared to a traditional conventional tillage polyethylene mulch system. Results reveal the integrated system provided successful alternative weed control practices compared to traditional systems. Due to this research, Extension, USDA-NRCS and growers increasingly recommend and adopt integrated weed management recommendations that control weeds, decrease economic risk, and protect the environment. Alabama Department of Agriculture and Industries contributed funding for the researcher’s collaborative work evaluating conservation specialty crop systems.
3. Cover crop residue delays start of the critical period for weed control in cotton. Due to unprecedented herbicide resistant weed yield loss, the urgent need for integrated weed management strategies was highlighted in a Weed Science journal special issue “Herbicide Resistant Weeds” containing a brief best management practice (BMP) section entitled “Cover Crops and Synthetic Mulches” describing the need to understand diverse BMPs, including “cultural management techniques that suppress weeds”. The critical period for weed control (CPWC) is the time interval in crop growth when a weed-free state must be maintained to prevent substantial (=5%) yield loss. In a CPWC study by ARS scientists in Auburn, Alabama, evaluating three systems, rye biomass suppressed early season weed biomass and extended the CWFP, thus delaying the start of the CPWC. The presence of a high residue rye cover crop delayed the critical timing for weed removal (CTWR) approximately 8 days compared to fallow treatments. Thus, winter fallow should be avoided to minimize cotton yield loss in conservation systems. Due to this research, Extension recommendations for integrated weed management are being revised to reflect weed suppressive attributes high-residue cover crops provide when establishing weed management strategies in conservation tillage cotton. Producers and crop advisors are more likely to utilize high residue cover crops if they understand the benefits and challenges conservation systems provide. Cotton Incorporated contributed funding to the researcher for this work.
4. Cover crop species response to nitrogen fertilization. Producers have been reluctant to spend money for fertilization of winter cereal cover crops because they are not harvested for feed or grain as other cash crops, although nitrogen (N) fertilization is typically required to maximize cover crop biomass and related benefits across coarse-textured soils of the Southeast. Nitrogen response across different winter cereal species (oat, ryegrass, and rye) was examined by ARS scientists in Auburn, Alabama, in a 4-year experiment to determine cover crop biomass production and N fertilizer use efficiency. Maximum biomass levels were measured with the greatest N rates applied, but rye was the most responsive to N applications. Nitrogen uptake efficiency values averaged 57%, 54%, and 21% for rye, oat, and ryegrass. Results represent the first N fertilizer research designed to develop cover crop N fertilization management guidelines for growers in contrast to examining how a fertilized cover crop or legume affects N requirements for the subsequent cash crop. Results have contributed to a national Natural Resource Conservation Service (NRCS) webinar, as part of training for employees, and an on-demand webinar available through the Plant Management Network website under the Focus on Cotton tab to educate viewers about how cover crop management decisions affect soil health and benefits for subsequent crops in the Southeast. The American Society of Agronomy also selected the corresponding publication as the basis for a self-study exam distributed to the current 13,000 certified crop advisors (CCAs) in the U.S.
Review Publications
Kornecki, T.S., Prior, S.A., Runion, G.B. 2018. Innovative method for cover crop termination using engine exhaust heat. European Agrophysical Journal. 5(4):145-156.
Balkcom, K.S., Duzy, L.M., Price, A.J., Kornecki, T.S. 2019. Oat, rye, and ryegrass response to N fertilizer. Crop, Forage & Turfgrass Management. 5:1-6. https://doi.org/10.2134/cftm2018.09.0073.
Korres, N., Bararpour, T., Slaton, N.A., Price, A.J. 2018. Effects of salinity on rice and weeds: Short- and long-term adaptation strategies and weed management. In: Hasanuzzaman,M., Fujita, M., Nahar, K., Biswas, J., editors. Advances in Rice Research for Abiotic Stress Tolerance. Cambridge, MA: Publishing/Elsevier. p. 159-176.
Li, X., Grey, T., Vencill, W., Freeman, M., Price, K., Cutts III, G., Price, A.J. 2018. Evaluation of cotton responses to fomesafen-based treatments applied preemergence. Weed Technology. 32:431-438. https://doi.org/10.1017/wet.2018.31.
Price, A.J., Korres, N., Norsworthy, J., Li, S. 2018. Influence of a cereal rye cover crop and conservation tillage on the critical period for weed control in cotton. Weed Technology. 32:683-690. https://doi.org/10.1017/wet.2018.73.
Price, A.J., Williams, J., Duzy, L.M., McElroy, S., Guertal, B., Li, S. 2018. Effects of integrated polyethylene and cover crop mulch, conservation tillage, and herbicide application on weed control, yield, and economic returns in watermelon. Weed Technology. 32(5):623-632. https://doi.org/10.1017/wet.2018.45.
