By Lynn Byczynski
Many farmers grow mixtures of cover crops to multiply the benefits of a planting. The most common approach is to grow legumes and grasses together. Some popular combinations include hairy vetch or red clover plus winter rye in cold winter areas or bell beans plus oats in milder winter areas. A legume-grass combination offers several benefits:
- Legumes and grasses grown together balance the carbon-to-nitrogen ratio in the soil after plow-down. The legumes, rich in nitrogen, break down quickly while the carbon-rich grasses take longer to decompose. Growing the two together makes nitrogen available to help break down the grass residue and reduces the amount of time that must elapse before a subsequent crop can be planted.
- A faster-growing crop such as oats or winter rye serves as a nurse crop to shelter less-robust, slower-growing plants such as red clover or sweet clover. Grasses establish quickly and prevent the growth of weeds that would otherwise compete with the legume.
- Low-growing crops and taller crops planted together cover more of the soil and do a better job of preventing erosion and weeds. Sorghum grows tall, and cowpeas grow low; together they shade the soil and prevent weed seeds from germinating.
- Legumes increase nutrient content of a hay crop that is to be used for livestock.
- Combinations of cover crops reduce the risk of crop failure and allow for differences in conditions across a field. In spots where a legume doesn't establish well, the grass may do better and vice versa.
• An Introduction to Cover Crop Species for Organic Farming Systems, from the eOrganic network.
• Overview of Cover Crops and Green Manures, by ATTRA, the Sustainable Agriculture Information Service.
Lynn Byczynski is the editor of Growing for Market and the publisher of The Hoophouse Handbook.