Cover crops of rye or wheat established after corn or soybean grain harvest can still provide excellent soil protection in spring, recycle nutrients, and improve soil
Cover crops are an essential part of sustainable cropping systems, particularly in no-till. Cover crops serve many purposes including:
- Improvement of soil health due to additions of organic matter and the effects of living roots on soil biology, soil physical properties, and soil fertility. We are learning that the rhizosphere (the region of soil immediately around the root) is like a super highway for soil organisms such as bacteria, symbiotic fungi, and protozoa that scavenge and process nutrients, contribute to building soil structure, and compete with pest and disease-causing organisms.
- Recycling of soil nutrients. There is increasing evidence of the importance of cover crops for taking up nitrates from the subsoil and releasing them upon decomposition of the cover crop, making it available to the next crop. This is done by a careful management of species, planting date and the C:N ratio of the cover crop at termination. Although we don’t talk too much about it yet, cover crops also recycle many other nutrients and some cover crops make sulfur available to successive crops.
- Providing weed control. Weed suppression provided by cover crops is likely to become more important as weeds develop increasing resistance against many herbicides. There is no silver bullet for weed control but cover crops such as rye have been found to be very effective in suppressing winter annuals such as glyphosate-resistant marestail. Although cover crops probably won’t provide complete control they can dramatically reduce weed infestations and cause remaining weeds to be smaller, so they are more susceptible to be killed by herbicides.
- Increasing grazing acreage. The valuable role of grazing animals for soil health is becoming clearer to us. It is interesting how the negative effect has been emphasized for such a long time, but the positives ignored. Grazing livestock can process high-carbon, fibrous plant material and make it more digestible for soil organisms. It is always amazing to me how earthworms will congregate below manure pies, but earthworms are only the top of the iceberg – there are many other soil organisms that are concentrated there. There is also evidence that the nitrogen value of urine from grazing animals is greater than that of applied manure as it is deposited in a concentrated area and infiltrated rapidly, protecting nitrogen from volatilizing.
These are just a few benefits of cover crops. The season has almost gone by, but there is still time to establish cover crops such as rye and wheat. They may not look like much in the fall, but come spring they can still put on significant growth. You may want to increase the seeding rate 25% because tillering is likely to be reduced in these late-seeded crops.