Beneficial Cover Crops
Over the past few years, the use of cover crops has increased as farmers, ranchers and land owners have found value in the numerous benefits of planting cover crops during or after traditional cash crops. A cover crop, also referred to as green manure, is a plant used between rows in a standing crop, or may cover an entire field between crops in a rotation. Cover crops are planted for many reasons. Cover crops slow soil erosion, improve soil health, add organic matter to the soil, enhance water availability, reduce soil compaction, use and store nitrogen that would be lost by leaching, aid in weed control, and can be used for grazing or forage production. Cover crops also increase the number of plant types or crops in the rotation.
At the West Central Research and Outreach Center (WCROC), nearly 50% of our crop acres are on certified organic land, largely for the purpose of supplying feed to a portion of our dairy herd. We grow corn, wheat, oats, and alfalfa. Cover crops play multiple, important roles within our crop rotation. We planted sorghum and tillage radish in one field after wheat harvest. In early-September 2015, we grazed heifers on the sorghum for three weeks. After the heifers were moved to another pasture, tillage radish grew back providing more plant diversity in the field. In this case, very little of the plant nutrients were removed from the field despite the three weeks of grazing. If this field had been left bare after wheat harvest, nitrogen would have leached from the soil making it problematic for next year’s crop. Instead, most of the nitrogen is tied up in an organic form in the plant material and in the manure which will be available for next year’s crop growth.
We also incorporate the use of cover crops in our manure management plan. In August of 2015, we applied liquid swine manure to an oat field. The concern when applying manure early (prior to fall) is nitrate leaching. To get around this, we planted tillage radish as a cover crop. Tillage radish has a deep tap root that can absorb and use the nitrate that would otherwise be lost.
To get the most benefit out of cover crops, one must consider what the crop will be used for. In our case, cover crops offer an organic method for replacing nitrogen to the soil, aid in weed control, allow for grazing cattle, and slows soil erosion.