Winter cover crops and no till management enhance enzyme activities in soybean field soils

Authors: Tyler, Heather

Submitted to: Pedobiologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2020
Publication Date: 7/17/2020
Citation: Tyler, H.L. 2020. Winter cover crops and no till management enhance enzyme activities in soybean field soils. Pedobiologia. 81-82:150666.

Interpretive Summary: Agricultural production of row crops, such as corn, cotton, and soybean, can have negative impacts on soil quality, increasing erosion and decreasing soil organic matter as well as microbial communities that mediate nutrient cycling in soils. Various conservation management practices have been employed to mitigate these negative effects, including no till management and planting cover crops to serve as ground cover during the winter. Scientists from the USDA-ARS Crop Productions Systems Research Unit in Stoneville, MS conducted a three-year field study to examine the effects of two different cover crop species, Elbon rye and Crimson clover, under till and no till conditions, on the size and activities of the microbial community in Mississippi Delta fields soils under soybean production. Both no till management and cover crops increased microbial biomass in field soils. Cover crop had a stronger influence on enzyme activities associated with organic matter breakdown than tillage, while both tillage and cover crop impacted activities associated with phosphate mineralization and general hydrolytic activity. Clover plots occasionally had lower activities compared to rye, but overall, the differences between cover crop species were very small in magnitude. No till plots had slightly higher yields compared to tilled, while rye plots had lower yields compared to clover and no cover treatments. This study demonstrates the importance of evaluating cover crops for their effects on both soil quality as well as yield. These results will help guide future cover crop research on finding varieties and implementation techniques to improve soil health while maximizing crop yield.

Technical Abstract: Conventional agriculture has negative effects on soil quality and downstream ecosystems. Eliminating tillage and planting winter cover crops are two conservation practices employed to minimize these negative impacts, improving soil structure, reducing erosion, and leading to the accumulation of plant residues in soil. The purpose of the current study was to assess effects of no till management and two different cover crop species, Elbon rye (Secale cereal L.) and Crimson clover (Trifolium incarnatum L.), on microbial biomass and enzyme activities (phosphatase, ß-glucosidase, N-acetylglucosaminidase, and fluorescein diacetate [FDA] hydrolysis) in lower Mississippi Delta soybean (Glycine max L.) field soils over a three-year period. Microbial biomass was elevated under no till and both cover crop treatments. Soil enzyme activities associated with organic matter breakdown were more impacted by cover crop than tillage, while phosphatase and FDA hydrolysis were impacted by both. Increased activities due to cover crop input appear to be the result of an enlarged microbial community as well as increased substrate availability. While these enhanced soil biological traits did not translate into higher soybean yields, longer evaluation periods are necessary to fully appreciate the benefits of improved soil health on long-term sustainability of crop production systems.