Effect of cereal rye cover crop on weed control, soybean yield and profitability

Authors: PINNAMANENI, SRINIVASA - Oak Ridge Institute For Science And Education (ORISE); SASEENDRAN, ANAPALLI - US Department Of Agriculture (USDA); Molin, William; Reddy, Krishna

Submitted to: Frontiers in Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2022
Publication Date: 7/22/2022
Citation: Pinnamaneni, S.R., Saseendran, A., Molin, W.T., Reddy, K.N. 2022. Effect of cereal rye cover crop on weed control, soybean yield and profitability. Frontiers in Agronomy. https://doi.org/10.3389/fagro.2022.907507.
DOI: https://doi.org/10.3389/fagro.2022.907507

Interpretive Summary: Crop management practices like no-till or reduced till along with cover crops are expected to enhance soil physico-chemical and biological properties pertaining to soil health, suppress weeds, reduce soil erosion and nutrients loss through surface runoff and possibly impact following summer cash crop returns. However, the earlier published reports revealed mixed results due to negative effects of rye cover crop on following cash crop. To address this, scientists with the USDA-ARS, Crop Production Systems Research Unit and Sustainable Water Management Research Unit, Stoneville, MS, conducted an experiment by varying rye dessication timings during 2019, 2020 and 2021. The results of the study indicated that no cover crop plot soybean recorded 13-15% higher yield than cover crop plots in the first year. In second and third year, rye cover crop plots had 10-13% yield advantage in soybean compared to no cover crop. This study demonstrated that soybean producers in the lower Mississippi Delta can grow rye as a cover crop without compromising soybean yields and net returns.

Technical Abstract: Considerable variations in farm productivity were reported across soils and climates when winter cover crops (CC) were rotated with summer main cash crops. Hence, a three-year field study (2019-2021) was conducted on Dundee silt loam in a humid climate to assess soybean growth and yield, weed control, and profitability under no-till conditions in response to (i) no CC (NC), (ii) winter rye CC rolled when green, followed by soybean planting and desiccation by paraquat (GR) and iii) winter rye CC desiccated using paraquat and rolled followed by soybean planting (BR). No differences in phenological growth stages of soybean were observed among the treatments. Measured leaf area index was comparable among the treatments across the three seasons. The rate of rye CC biomass decay estimated eight weeks after planting (WAP) was much higher than at four WAP. In 2019, at eight WAP plant residue ranged from 29.3% under NC to 52.9% under GR, indicating the paraquat desiccated natural winter vegetation decays faster than the desiccated rye CC biomass. The weed biomass was 72% higher at eight WAP (0.29 Mg ha-1) than that of four WAP (0.17 Mg ha-1) and NC plots had higher weed biomass at both four WAP and eight WAP over CC plots. Field established soybean stand in the GR plots were consistently higher than the NC plots by 8%, 30%, and 22% in 2019, 2020, and 2021, respectively. Soybean yield in NC plot was 13% higher than GR and 15% higher than BR plots in 2019. However, in the 2020 and 2021, soybean yield from BR and GR plots was significantly higher than NC plots (10 % and 13%, respectively). In the three-year study, net returns from soybean with rye CC (regardless of GR or BR) in the first year was negative. In the second and third year, net returns in GR and BR were positive and comparable to NC. There were no differences in soybean yield and net returns between rye CC rolled green (GR) and rye CC desiccated (BR) prior to planting. These results show that a rye CC–based soybean conservation production system could be an economically a viable choice after the first year with an invaluable potential to mitigate climate change through carbon sequestration.