Moisture conditions across the state may have people considering growing cover crops this year. Wheat harvest is just around the corner and many wheat producers in central South Dakota have found that cover crops planted after wheat can provide some benefits. This year with the positive moisture situation across many areas of the state, cover crops after wheat harvest will be an excellent fit.
Cover crops can also offer an opportunity for producers who are dealing with “prevent plant” acres in 2014. Getting something growing where they have not been able to plant a crop will help to ensure long-term productivity in those areas.
It has been determined through research that cover crops offer more benefits if they are composed of numerous species. Planting a cover-crop mixture will add more diversity. Different species each offer their own characteristics to the entire cover crop mix. Some species provide more carbon to the system, some better compete with weeds, some grow better in cool weather and others grow better in warm weather, some provide better forage, some are better at penetrating a hardpan and some are better at sequestering nitrogen.
Choosing or developing a cover crop mix can be complicated. There are many options to consider. A good starting point is to determine the objective of the cover crop. What do you want the cover crop to accomplish? In most situations producers have more than one objective in mind for a cover crop. It is important to prioritize objectives and aim at selecting a cover crop mix that will satisfy one or two of the top goals and possibly some of the others as well.
For producers interested in growing a cover crop on acres that have been too wet to seed to a traditional crop, objectives might include; using excess moisture, reducing sideways movement of water and saline seep development, reducing weed growth and seed production, sequestering nutrients, reducing erosion and potential for compaction. The NRCS lists numerous cover crop species and their characteristics.
The USDA-ARS Northern Great Plains Research Lab at Mandan, ND has also developed a Cover Crop Decision Aid.
Cover crops can also provide producers with the opportunity to extend the grazing season. Cover crop mixtures seeded now or after wheat harvest can provide a very high quality fall forage. Crude protein values may range from 5 to 25 percent with a relative feed value close to 300.
Other important considerations when choosing a cover crop include:
Be sure that residual herbicides from the previous crop will not affect the cover crop
Try to keep seed costs down by using seed already on hand when possible
Be sure to consider what was planted before and after the cover crop when determining species in the mix. In other words avoid species that act as hosts to pest cycles. Cover crops are part of the crop rotation and the same rules apply.
Small seeds grow better on the surface than larger seeds. Large seeds usually emerge better through a mat of residue.
Consider using the cover crop to balance the diet of the soil organisms. High carbon residue (low protein) requires low carbon (high protein) cover crops to balance the diet. Low residue crops (low C) require high carbon (high residue) cover crops.
Some species such as corn, sorghum, milo and flax are known to improve levels of mycorrhizal fungi in the soil. These are beneficial fungi which can help plants obtain nutrients from the soil. A small amount of any of these species in a cover crop mix is a good addition for this reason.
The flax plant has the vertical architecture that can help catch snow and reduce wind erosion during the winter in areas where there is little or no residue.
If considering a cover crop, producers are advised to check with the local FSA and their crop insurance agent to determine any specific requirements or harvest restrictions for cover crops.