Proponents say that rotating cash crops such as soybeans, wheat and corn with cover crops such as legumes, grasses and forbs has many benefits. It replenishes the soil, reduces erosion, cuts down on runoff pollution and helps to control pests. However, many farmers don’t use cover crops because they believe it cuts into their bottom line. There’s the cost to plant the cover crops and the cost of removing them when it’s time to switch back to cash crops, which to many seem to outweigh whatever benefits conferred by improved soil health.
Studies into the economic sense of planting cover crops have so far have been inconsistent. A crop cover survey of 2,000 farmers taken in 2015-16 revealed that only one-third saw an increase in profits during the year. Most reported that they lacked the data or that there was no change.
However, few studies have economically compared cover crops under controlled conditions where some fields were planted with cover crops of different varieties, some grass, and some left uncovered over a period of years.
To uncover what’s going on with cover crops, University of Missouri College of Agriculture, Food and Natural Resources (CAFNR) researchers Zhen Cai and Ranjith Udawatta did such a study of the economic effects of cover crops on cash crop production. The four-year study took place at the Natural Resources Conservation Service (NRCS) Soil Health Farm in Chariton County, Missouri, in a 26.3-hectare (64.9-acre) area, which was divided into six fields and planted with soybeans, corn and wheat.
During the study, they measured the annual profitability of corn, wheat, and soybean production both with and without a cover crop in the rotation. As part of the study, they examined the cost of planting, maintaining, and terminating the cover crop, the cost of the cash crop, cash crop revenues, and the yields of the cash crop.
“We found that economic profitability of the cash crop is negatively affected by the cover crop during the first two years but were positive in the fourth year,” says Cai. “In the short term, the cost associated with the cover crop has a negative economic impact on cash crop production. However, a positive impact may occur in subsequent years because of improved soil health and yields.”
Udawatta says that cover crops impact the health of the soil in several ways.
“Cover crops keep soils covered and thereby reduces the impact of rain drops, which reduces soil detachments and erosion,” says Udawatta. “Live cover keeps all soil organisms active by providing food and buffering adverse conditions and thereby protecting soils, improving fertility, and carbon and water holding capacity.”
Their work supported a recent case study conducted by the NRCS in 2015 in Missouri where it was found that adding a cover crop to a corn–soybean rotation was initially economically costly, it could potentially be profitable in the long term.
Cai and Udawatta stress that more data are needed on the economic impact of cover crops before any policy judgments concerning financial assistance for farmers using cover crops can be made. They say that payments are essential in the short term to encourage the use of cover crops. Long-term help may encourage the use of cover crops but may not be necessary if the benefits of cover crops markedly improve the profitability of cash crops through improved soil health.
Collaborators on the project include Clark Gantzer, professor emeritus, soil science; Shibu Jose, CAFNR’s interim associate dean for research; Larry Godsey, associate professor, Missouri Valley College; and Lauren Cartwright, natural resource specialist/agricultural economist at NRCS. For additional information on this study, read Economic impacts of cover crops for a Missouri wheat-corn-soybean rotation.