Cover cropping is the practice of growing plants to protect and improve soil rather than for harvest. Cover crops prevent Erosion Control, suppress weeds, scavenge residual nutrients, fix nitrogen from the atmosphere, and add organic matter. Common cover crop species include cereal rye (Secale cereale), crimson clover (Trifolium incarnatum), hairy vetch (Vicia villosa), winter wheat (Triticum aestivum), and buckwheat (Fagopyrum esculentum). Cover crops are typically grown during fallow periods or intercropped with cash crops.
Cover cropping has been practiced since antiquity. Roman agricultural writers such as Columella described the use of green manures to restore soil fertility. In the 20th century, the Dust Bowl of the 1930s in the United States spurred widespread adoption of cover crops for erosion control. The modern No-Till Gardening and conservation agriculture movements have further promoted cover cropping as a core soil management practice.
Nitrogen-fixing cover crops, including legumes such as clover, vetch, and peas, host rhizobium bacteria in their root nodules that convert atmospheric nitrogen into plant-available forms. A well-managed hairy vetch or crimson clover stand can fix 90 to 170 kilograms of nitrogen per hectare (80 to 150 pounds per acre). Grasses and cereals such as rye, wheat, and oats are grown primarily for biomass production, erosion control, and nutrient scavenging. Brassicas like forage radish and rapeseed have deep taproots that break up compacted soil layers.
Cover crops are terminated before planting the main crop. Mechanical methods include mowing, rolling (crimping), and tilling. Each crop species has a specific termination window: legumes are terminated at early flowering for maximum nitrogen contribution, grasses at boot stage for maximum biomass. Herbicides are used in conventional systems but are generally avoided in organic and regenerative approaches.
Cover crop residues protect the soil surface from rain impact, reducing erosion and runoff. The root systems improve Soil Composition by creating pore spaces and adding organic matter. Decomposing residues feed Soil Biology, including earthworms and mycorrhizal fungi. Cover crops also suppress weeds through competition and allelopathy, particularly cereal rye, which releases compounds that inhibit small-seeded weed germination.