Cover crop

What is a cover crop?

In most crop rotations, fields sit bare for months between harvest and the next planting. A cover crop fills that gap with living plants, whose roots hold soil and feed soil organisms, and whose residue protects the surface. Cover crops are usually terminated, by herbicide, rolling, mowing, tillage or winter kill, before or around planting of the next cash crop. The USDA Natural Resources Conservation Service supports cover cropping as a conservation practice.

Common cover crop types

• Grasses and cereals, such as cereal rye, oats and wheat, which produce large amounts of biomass and scavenge leftover nitrogen.
• Legumes, such as crimson clover, hairy vetch and field peas, which host rhizobia and add nitrogen through biological nitrogen fixation.
• Brassicas, such as radishes and turnips, whose taproots can penetrate compacted layers.
• Mixes of several species to combine benefits.

Benefits

• Erosion control from continuous ground cover.
• Nutrient retention, capturing nitrogen that could otherwise be lost to leaching. See nitrogen loss.
• Soil structure and water infiltration, through roots and increased soil organic matter.
• Weed suppression.
• Support for the soil microbiome, which is fed by living roots.

Management considerations

Establishment costs, planting windows after harvest, termination timing, water use in dry regions, and possible effects on the following crop, such as nitrogen tie-up after a cereal cover, all affect results. Benefits often build over several years. Cover crops are commonly paired with no-till farming as part of regenerative agriculture.

Frequently asked questions