Cover Cropping to Increase the Sustainability of Cropping Systems by Developing Soil Organic Matter, Improving Soil Health, and Suppressing Weed Growth

View the project final report

Commodities

• Agronomic: soybeans

Practices

• Crop Production: cover crops
• Education and Training: on-farm/ranch research
• Soil Management: organic matter, soil analysis, soil quality/health

Degrading soil health, biodiversity, and soil resilience are major challenges to sustainable crop production under changing climates (Freckman and Virginia, 1997). Excessive tillage, inappropriate crop rotations, monocultures, excessive grazing or crop residue removal have degraded soils in the Southern U.S. crop production systems. Recent extreme climatic events that drastically affected the South have exacerbated soil degradation in this region. Soil health is strongly related with beneficial soil and ecosystem functions including water storage, decomposition, and nutrient cycling; and responds sensitively to land management practices and climate. According to the Organic Farming Research Foundation survey among farmers (National Organic Research Agenda, 2016), 42 percent of respondents in the Southern US demanded more research to identify cultural practices to improve soil health that would improve the resilience of production systems to extreme weather. Recently, much attention is being focused on cover cropping as a sustainable practice to achieve these goals.

Reducing weed pressure on crops without affecting soil health through intense and frequent tillage and cultivation practices is a major challenge in sustainable crop production. With the increasing interest toward organic grain production in the Southern U.S., fall cover crops could be explored as a sustainable practice that reduce weed pressure, as well as improving soil health and cropping system intensity and diversity. Even though the multiple functions make cover crops a whole-farm system approach for improving sustainability and profitability of cropping systems, few producers in the South have included cover crops as part of their cropping systems. A major reason being lack of knowledge regarding the suitable cover crops for their locality that lead to improved use of resources and soil health. In addition, farmers often ask, "Why should I plant a cover crop that uses up all my water?"

To address this issue, we conducted a study (2016-2017 and 2017-2018 field seasons) to evaluate the common fall cover crops in South Carolina for water use with the financial support of the Southern SARE On-Farm Research Grant program. In this preliminary research, we evaluated seven cover crop treatments (rye, crimson clover, rye/crimson clover mixture, oat/ radish mixture, crimson clover/turnip mixture, oats/wheat/crimson clover/radish/turnip mixture, and Austrian winter peas/rye/wheat/crimson clover/hairy vetch mixture. First year results indicated that none of the cover crop treatments depleted soil water more than a fallow control. We identified certain single cover crop species and mixtures that utilize water efficiently and that would actually increase soil moisture for the following cash crop.

In the current proposed study, we will determine the effect of four selected fall cover crops that conserve soil water for the following cash crop, based on the results from the Southern SARE-funded preliminary research, on soil health, including addition of organic matter and weed suppression, and their impact on the performance of the following cash crop in an on-farm trial.

We will evaluate cover crops belonging to brassica, grass and legume groups, as individual species and in mixtures for their benefits to soil health and weed suppression.

We will measure soil health parameters and weed growth during the cover crop season and/or subsequent cash crop (soybean) season. The cover crop treatments will be compared with that of two control treatments: fallow with herbicide control (weed-free) and fallow without herbicide control (with weeds).

We anticipate that the best cover crop(s), which are already found as water savers in the preliminary research, will also retain maximum amount of soil nutrients, increase organic matter, improve soil health, and suppress weed growth for the subsequent soybean crop. Measurement of soybean biomass and seed yield will determine whether/how cover crops have improved the performance of the following cash crop.