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ISU officials say soybeans can be considered good farming practice when used as cover crop on prevented planting acres

By Jean Caspers-Simmet

Date Modified: 07/16/2013 3:21 PM

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AMES —Some farmers are considering planting soybeans as a cover crop on prevented planting acres.

In his July 3 Crop Notes, Brian Lang, Iowa State University Extension field agronomist for crops, said many questions have been asked about using soybeans as a cover crop on prevented planting acres.

Discussions with the Risk Management suggest that the agency isn't going to issue a decision on the issue. Lang said some crop insurance companies are using the "advice from a crop expert" clause regarding insured crop seed as a cover crop and sending farmers to ISU to get a letter.

"ISU recognizes that soybean is not the preferred cover crop based on Prevented Planting guidelines, but we believe that using soybeans addresses two concerns," Lang said. "First, they are better than no ground cover. Second, it provides for proper disposal of treated soybean seed that cannot be returned into the supply chain and likely will not be viable for next spring."

Lang included a July 3 letter written by John Lawrence, associate dean for Extension programs; Roger Elmore, Extension corn agronomist; and Andy Lenssen, Extension cropping systems agronomist; that is ISU's response to the "advice from a crop expert" clause.

The letter said soybeans "can be an agronomically sound cover crop option for Iowa growers on Prevented Planting Acres. This, however is not a common practice for Iowa corn and soybean farmers and is not without its drawbacks."

Lang advises farmer intending to use soybeans as a cover crop on prevented planting acres to be certain they have approval from their insurance companies to do so.

In their letter Lawrence, Elmore and Lenssen said soybeans as a cover crop should provide effective erosion control, may improve soil quality as legume and will provide some degree of weed control. Beans likely will mitigate issues with fallow-soil syndrome in the 2014 cropping season.

Lawrence, Elmore and Lenssen offered some agronomic considerations.

They said that soybeans as a cover crop must be planted at a reduced seeding rate. A suggested rate is 50 pounds pure live seed per acre. Recommendations for late-planted soybeans harvested for grain are considerably higher, but 50 pounds PLS will suffice if good stands are achieved.

If farmers broadcast soybeans as a cover crop, seeding rates double the 50 pound PLS are justified from an agronomic perspective since seedling establishment will be compromised. If seed is treated, it should be incorporated once broadcast to prevent problems with wildlife.

Broadcast seeding, drilling or planting soybeans in narrow rows and higher planting rates will result in more rapid canopy closure and better erosion and weed control. Farmers should make certain that any previous herbicide applications won't affect soybeans.

"Other crops like sorghum-sudangrass, among others, may provide a better option than soybeans as cover crops in prevented planting," Lawrence, Elmore and Lenssen wrote.

The ISU experts concluded that "soybeans can be considered a good farming practice when used as a cover crop on Prevented Planting Acres."