Cover Crops
“What are cover crops?” The term cover crop has been used more in the last 3 years than it has in the previous 15. Cover crops are generally considered any crop planted on a field between cash grain crops or during the non-growing season to provide “cover” to the soil. In the Midwest, the non-growing season typically starts after corn or soybean harvest, sometime between September and mid-November. Most cover crops get seeded during this period. Cover crops are terminated (using chemicals or tillage) in early to mid-spring either prior to or immediately following planting the cash crop.
Before the advent of commercial fertilizer, cover crops were used mainly as a “green manure” crop that was plowed under in the spring to provide nutrients for the next crop. Today, the theory behind cover crops is multifaceted, and includes but is not limited to:
1. Improving organic matter and soil structure
2. Protecting the soil from wind and water erosion
3. Suppressing weed pressure
4. Maintaining nutrients in the soil
5. Improving microbial activity
6. Reducing compaction
7. Producing nitrogen
One of the main benefits of planting cover crops is to improve soil and water conservation. The soil cover provided by the cover crop, along with the roots growing under the soil surface provide a dual level of protection for the soil. The plant cover reduces the impact of raindrops on the soil and protects the surface from wind erosion. The roots open pathways for water to infiltrate the soil instead of running off. To the contrary, water running across the surface often carries soil particles and nutrients along with it, which is not desirable.
In addition to protecting nutrient loss from runoff, cover crops capture excess nutrients remaining in the soil after the cash grain crop is harvested and recycle them for the next crop, as the cover crop will slowly release these excess nutrients as it deteriorates after termination in the spring. Nutrients tied up in the cover crop won’t move into streams and creeks and add to nitrate or phosphorus levels in the spring.
Challenges of Cover Crops
Weather conditions and pest pressure can pose challenges to adding cover crops to your management system. In some cases, cover crops may attract pests such as army worm moths to lay eggs early in the Spring, which can lead to increased pest pressure in the following cash crop. Additional management, such as applying an insecticide as part of your cover crop termination program may be required.
If your farm is not well tiled or receives excess rainfall in the Spring, a layer of cover crop residue can slow soil warm up and delay planting significantly. This issue can be resolved by planting a cover crop that does not survive the winter, changing the cover crop termination date, or using tillage to terminate the cover crop. While adding tillage to the program negates some of the soil conservation benefits of cover crops, it may be necessary in some instances. Even with tillage, the additional organic matter incorporated into the soil will help water holding capacity and soil tilth, so there will still be some conservation benefits versus the same field without a cover crop.
Another challenge, especially in the upper Midwest, is the timing of the seeding. If your farm is located in the Dakotas, Wisconsin, Minnesota, or the northern tier of counties in Iowa, the cover crop may need to be inter-seeded while the commodity crop is still in the field, to allow the cover crop adequate time to grow and gain the benefits prior to winter weather. This can be accomplished in a number of ways including aerial seeding of the cover crop from a plane.
Cover Crop Options
There are a number of effective cover crops that can be used depending on what your goals and objectives are for the cover crop seeding. Most commonly these cover crops are cereal rye, oats, turnips, and radishes. Additional options would be hairy vetch, sweet clover, rye grass, lentil peas, sugar beets, and soybeans.
Certain cover crops such as sweet clover and hairy vetch will fix/add nitrogen for use by the following cash crop. Fall cover crops, such as rye, can make great forage for livestock during the fall/winter and again in the spring. Some cover crops, such as tillage radishes can help manage compaction and aerate the soil better than others. Other cover crops, like oats, die during the winter, which eliminates the need to terminate them in the spring allowing for earlier planting of the cash crop and reducing the need for tillage in the spring.
Cover crops can be a great tool in the stewardship of your land, but the right type of cover crop can vary depending on your overall crop rotation, field conditions, and location of the farm. All these factors and more need to be considered when determining which cover crops may fit best for your farm. Please feel free to contact a Hertz Farmland Professional if you would like additional information on cover crops for your farm.
