Cover Crop Influence on Stored Soil Water Availability to Subsequent Crops

View the project final report

Commodities

• Agronomic: soybeans

Practices

• Crop Production: cover crops, water management
• Education and Training: on-farm/ranch research

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. South Carolina SARE Program farmer stakeholders have identified "cover cropping for weed management" as the highest priority topic for research and training. With the increasing interest toward organic grain production in the southeastern US, fall cover crops could be explored as a sustainable practice that improve cropping system intensity and diversity as well as improving soil health and reducing weed pressure. Despite the potential benefits, few grain producers in the southeast have included cover crops as part of their cropping systems because of several challenges. One of the major concerns of producers is the possibility that cover crops may reduce the amount of water stored in the soil profile for the next grain crop, potentially reducing yields. Therefore, it is imperative to test the effect of cover crops on stored soil water before they are introduced to the cropping system for sustainably managing weeds and improving soil health.

The objective of this study was to evaluate the common cover crops in SC for soil moisture retention and biomass production. We evaluated seven cover crop treatments including grasses, legumes, and brassicas as single species or in mixtures, and compared them with two controls, a weed-free fallow and a weedy fallow, in an on-farm trial. Soil moisture content was measured at 10, 20, 30, 40, 60, and 100 cm depths at approximately biweekly intervals during cover crop season and at one month after termination. Biomass was measured at monthly intervals during the cover crop season. We found that all cover crop treatments retained more or equal amount of soil moisture compared to controls (weed-free or weedy fallow). Rye and a mixture of Austrian winter pea, crimson clove, hairy vetch, oat, and rye were good ground covers in terms of number of plants per meter square, and had highest amount of biomass and water use efficiency values. Though the mixture of turnip and crimson clover and crimson clover retained good amount of moisture in the soil, they were poor biomass producers and ground covers. Taken together, our results will provide information to develop grower recommendations on specific cover crops to optimize biomass and soil moisture for subsequent crops.

Evaluate the common fall cover crops in South Carolina for water use, biomass production, and water use efficiency to identify cover crops that improve available soil moisture for the following cash crop.