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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Research Project #435668

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

Location: Soil Dynamics Research

2019 Annual Report

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.
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.
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.
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.