Dale R. Mutch
Cover Crop/IPM Specialist
MSU Kellogg Biological Station

On the New Ag Network organizational conference call on July 24, some farmers had questions about seeding cover crops in the latter part of summer. Two cover crops in particular were mentioned – hairy vetch and soybeans.

Hairy vetch
Hairy vetch is a winter annual legume that will produce high levels of nitrogen. In Michigan, we try to plant hairy vetch between August 1 and September 1. In a biomass study conducted at MSU/KBS we saw a 2,000 lb. increase in spring biomass by planting hairy vetch on August 25 as compared to September 14 in 2005.

Hairy vetch has a tendency to re-grow in fields where it has been planted. This can cause problems particularly in small grains. The seed of hairy vetch is really hard to separate from small grains. Farmers need to remove hairy vetch plants similar to weeds when in small grains. To summarize, I would plant hairy vetch after August 1. The date should be modified to consider soil conditions. For example, if your soils have adequate moisture, I would plant earlier. But if your soil conditions are very dry, I would wait until the conditions are right.

Paul Mugge from Iowa had a good suggestion. He was going to prepare his fields for seeding now and when he receives some rain he is going to seed his cover crops into the prepared ground.

Soybeans
We haven’t done too much work with soybeans as a cover crop. We did plant it after wheat harvest for several years to evaluate it. When we compared soybeans to oilseed radish, hairy vetch and crimson clover, soybean biomass was the lowest. We seeded soybeans at the one bushel rate and I believe we should have planted it at a higher rate of 2 to 3 bushels per acre.

If you want to seed soybeans as a cover crop, I would plant it as soon as possible, especially if you want soybeans to nodulate and produce some nitrogen for next year. Floyd Johnson from Illinois mentioned that soybeans may provide more nitrogen benefits for next year if you produce beans and then work them into the soil. A lower rate of soybeans will enhance seed production and I would recommend 1.5 bushels per acre if this is your intent.