cover crop

noun1

1. •
   Any of many crops planted between others or after others so as to prevent erosion and to improve soil quality (especially by adding nitrogen); such a crop is often plowed into the soil as a green manure at the end of its season. Crops often used as cover crops include legumes (e.g., clover, sweet clover, vetch), cereals (e.g., rye, oats), and roots (e.g., radishes, turnips).