Cover crop does more than just cover and protect the soil after the main crop is harvested. It adds organic matter, improves soil quality, enhances nitrogen management, provides erosion control, brings up nutrients from deep soil layers, aerates the soil, and suppresses weeds and nematodes. Maintaining cover crops through fall, winter and early spring helps to reduce soil loss.
All cover crops supply extra organic matter to feed and breed beneficial soil organisms for soil fertility and soil health. The roots of certain cover crops can go down several feet below the topsoil and pull essential nutrients up to the topsoil level.
Some cover crops can weed out other plants. Buckwheat, oats, and sunflowers are good types of these allelopathic plants (plants that can inhibit the growth of other plants).
Some cover crops can attract beneficial insects and repel bad insects, like marigolds and crimson clover. Some legume cover crops, like white clover, can be planted next to your crops during the warm season to be used as living mulch.
Winter cover crop is planted in late summer or fall to provide soil cover during winter. Legumes are popular cover crops due to their nitrogen fixation ability. Popular legumes are crimson clover and hairy vetch.
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Summer cover crops can be used to improve the conditions of poor soils, or to prepare land for a perennial crop. Legumes such as cowpeas, soybeans may be grown as summer cover crops to add nitrogen along with organic matter. Non-legumes such as buckwheat are grown to provide biomass, smother weeds, and improve soil tilth.
Cover crops are also used as living mulch. Living mulch is a cover crop that is interplanted within garden, vegetable or ornamental, plants. Living mulches suppress weeds, reduce soil erosion, enhance soil fertility, and improve water infiltration.
All cover crops should be either tilled in, mowed down almost to the ground, or smothered by organic mulches before they go to seed, to prevent sprouting later in the year and becoming a weed themselves. The no-tilling option is the best way to get optimal soil health, texture, and soil microbial activity. Excessive tilling, or tilling too deep, can kill off beneficial fungi in the soil and create soil texture problems and some soil fertility issues. If you decide to go with a no-till garden, you can poke holes in the soil around crop roots with your spade fork, to get more oxygen in the soil to further increase organic matter decomposition and increase microbial activity in the soil. Year round cover crop practices can not only improve your soil health and texture, but also decrease extra periodic plant fertilizers and soil amendments.