Leopold Center - Cover crops in the Corn Belt: Survey finds underused potential as conservation tool

A wealth of scientific information exists on the benefits of cover crops, yet their use in conventional row-crop farming systems traditionally has been low. Scientists and educators have speculated about the reasons for low adoption, but these questions have never been posed to a large audience of producers, who are the end-users of this technology.

To learn more about cover crop use in the central western Corn Belt, we developed a survey that was mailed July 2006 to 3,500 producers in Iowa, Minnesota, Illinois and Indiana. In addition to the questions about why farmers did or did not use cover crops, we asked them about their farm type and size, familiarity with cover crops, and use of other conservation practices.

Survey results confirm that cover crop adoption in these states is low. Only 10.5 percent of the respondents in Iowa had ever planted cover crops, defined as any plants that cover the soil and are planted after the main cash crop growing season. Only 6 percent of the Iowa respondents had planted them within the past five years.

In Iowa, 28 percent of the respondents said they were not at all familiar with cover crops and 28 percent said they were either very familiar or moderately familiar with this practice.

The highest rate of cover crop use was 28 percent in Indiana, which typically has a longer growing season and window to plant and establish a cover crop. In both Illinois and Indiana, 15 percent of the respondents had planted cover crops in the past five years.

Perceived obstacles to cover crop use
When asked why they had never planted cover crops, farmers were asked to choose from several reasons (which are calculated for this analysis by state). Responses included:

Based on these results, time constraints, profitability and yield depression in subsequent cash crops do not appear to be significant impediments to cover crop adoption. Developing good cost estimates for cover crop establishment and cover crop management and uses may help producers determine the benefits and risks of using cover crops in farming systems dominated by summer annual crops.

Perceived benefits of cover crops
Farmers were asked about what they perceive to be the main benefits of cover crops. Between 84 and 87 percent listed a reduction in the amount of soil erosion, followed by an increase in soil organic matter, 60 to 71 percent. Other perceived benefits included a reduction of soil compaction and weed suppression.

Willingness to use cover crops
When asked about using cover crops if cost-sharing was available, 40 to 58 percent of the respondents said they would use them. Between 47 and 62 percent of the respondents said they had a grain drill or other equipment to plant cover crops, and 24 to 30 percent said they would use cover crops if they could custom hire the planting.

Most desirable traits for cover crops
Farmers were asked about characteristics they would look for in a cover crop. Desirable plant traits included:

Commonly planted cover crops
Among cover crop choices, winter wheat was more popular in Illinois and Indiana; winter rye was common in Illinois, Indiana and Iowa; and oat was common in Iowa and Minnesota. Red clover was the most common legume cover crop, appearing more often in Illinois and Indiana.

Cover crop adoption and the cover crop used reflect the different farming systems in each state. More wheat is grown in Illinois and Indiana than Iowa, so producers may save some of their wheat seed to plant a cover crop. Producers from these states also could have counted their cash grain wheat crop as a cover crop, although the survey defined cover crops as plants grown between cash crops.

The higher incidence of red clover in Illinois and Indiana also reflects the use of the red clover as an intercrop in wheat, which is a good source of nitrogen for a subsequent corn crop. Longer growing seasons in Illinois and Indiana also may contribute to increased cover crop use.

Conclusions
The results of this survey will be used to identify cover crop knowledge gaps and improve the dissemination of cover crop information. Cover crops may become more important in midwestern farming systems as producers add corn acreage with corn following corn becoming more common.

Cover crops may alleviate some of the yield depression that is documented in continuous corn, and continue to accumulate nutrients after the cash crop is harvested. Educational programs and targeted cover crop use on vulnerable sites in the landscape may increase cover crop adoption and contribute to protecting our natural resource base and maintaining productive soil.

The survey was funded as a special project of the Leopold Center Ecology Initiative to look at cover crop use and impediments to adoption in the central western Corn Belt. The survey was conducted by the Statistical Laboratory at Iowa State University.

It included 875 producers in each of four states: Iowa, Minnesota, Illinois and Indiana. The survey had a response rate of 36 percent, and eligible respondents had farmed in the past five years.

Survey respondents, by the numbers

Cover crops are literally “crops that cover the soil” and may be used to reduce soil erosion, diminish nitrogen losses, provide weed and pest suppression and increase soil organic matter.

Winter cover crops are planted shortly before or soon after harvest of the cash crop and are killed before or soon after planting of the next cash crop. Cereal grains, such as oat, barley, winter wheat, triticale and rye are excellent cover crops because they grow rapidly in cool weather, withstand moderate frost, and their seed is relatively inexpensive or can be produced on site.

Many varieties of winter rye, triticale and wheat can overwinter in the upper Midwest and continue growing in the spring. Growth of these winter-hardy cover crops must be terminated with herbicides or tillage prior to planting corn and soybean. Oat, barley, spring wheat and triticale, some rye and winter wheat are not winter-hardy in the upper Midwest. Because these cereal grains do not survive the winter, they do not require control prior to planting corn and soybean.

Corn yields may be reduced following winter-hardy cereal grain cover crops that are terminated immediately before corn planting. Yield reduction can be minimized by terminating cover crop growth more than 14 days prior to corn planting and using starter fertilizer. Corn yields following an oat cover crop or a legume that overwinters are not reduced. Soybean yields do not decrease following cereal grain cover crops unless low soil water content limits soybean germination and emergence.

More information is available in an Iowa State University Extension publication, Small grain cover crops for corn and soybean, PM 1999, available on-line at www.extension.iastate.edu/Publications/PM1999.pdf