A cover crop is a crop grown to improve the soil, repress weeds, or benefit subsequent crops grown in rotation. It is not intended to be harvested or grazed, although when small grains are used as cover crops a side benefit is that the timing of operations for cover cropping makes possible their use as forage (see Part 10, Small Grain Forages).

Small grains (including wheat, barley, oat, triticale, and rye) are useful as cover crops in many cropping systems because seed is relatively inexpensive, they produce large amounts of biomass quickly, and they have important soil-preserving properties. Small grains are excellent candidates as cover crops for many situations, including orchard, vineyard, and row crop acreage. Cultural practices (planting rates and dates, tillage, fertilization, and irrigation) for producing small grain cover crops are similar to practices for producing a regular grain or forage crop, except that lower fertilization and irrigation inputs are required and crop termination (through herbicide application or plowing under) is geared to the timing of the subsequent crop. Specific cultural practices vary from region to region of California, as does crop development (see Part 2,
Growth and Development; Part 3, Seedbed Preparation, Sowing, and Residue Management;
Part 4, Fertilization; and Part 5, Irrigation and Water Relations)