Basics of Cover Crops
Recently, on our Peaceful Valley Farm & Garden Supply Facebook page, there was a request made for more information about our cover crops. Being a newbie to the farming and gardening world, I was left scratching my head on where to even begin. After some scavenging around the internet and our own personal library, I am proud to say that I know now what a cover crop is! Through my researching process, I found a lot of great information concerning this topic, but one website in particular was especially helpful in answering my questions.
ATTRA, the National Sustainable Agriculture Information Service, features an entire article about cover crops called, "Overview of Cover Crops and Green Manures." Without this article, I might still be lost and for this reason I would like to dedicate this post on sharing some of the most helpful information found in the literature about cover crops. *This information was taken directly from the article, written by Preston Sullivan, NCAT Agriculture Specialist, in July of 2003.
Principle Uses of Cover Crops and Green Manures
"Green manuring" involves the soil incorporation of any field or forage crop while green or soon after flowering, for the purpose of soil improvement. A cover crops is the broad term for any crop that is grown to provide soil cover, regardless of whether it is later incorporated. Cover crops are most often used to prevent soil erosion from the wind and water and can be found as annual, biennial, or perennial herbaceous plants which are grown in a pure or mixed stand during all or part of the year. Cover crops do a number of things, some of which include: providing ground cover, helping to fight weeds and insect pests/disease, and in the case of legumes, fixing the nitrogen in your soil.
Winter Cover Crops
A winter cover crop is planted in late summer or fall to provide soil cover during the winter. Often a legume is chosen for the added benefit of nitrogen fixation. In northern states, the plant selected needs to possess enough cold tolerance to survive hard winters. Hairy vetch and rye are among the few selections that meet this need. Many more winter cover crops are adapted to the southern U.S. These cool-season legumes include clover, vetches, medics, and peas. They are sometimes planted in a mix with with winter cereal grains such as oats, rye, or wheat. Winter cover crops can be established by aerial seeding into maturing cash crops in the fall, as well as by drilling or broadcasting seed immediately following harvest.
Summer Cover Crops
A summer green manure occupies the land for a portion of the summer growing season. These warm-season cover crops can be used to fill a niche in crop rotations, to improve the conditions of poor soils, or to prepare land for a perennial crop. Legumes such as cowpeas, soybeans, annual sweetclover, sesbania, guar, crotolaria, or velvet beans may be grown as summer green manure crops to add nitrogen along with organic matter. Non-legumes such as sorghum-sudangrass, millet, forage sorghum, or buckwheat are grown to provide biomass, smother weeds, and improve soil tilth.
Benefits of Cover Crops and Green Manures
Organic matter and soil structure
A major benefit obtained from green manures is the addition of organic matter to the soil. During the breakdown of organic matter by microorganisms, compounds are formed that are resistant to decomposition--such as gums, waxes, and resins. These compounds--and the mycelia, mucus, and slime produced by the microorganisms--help bind together soil particles as granules, or aggregates. A well-aggregated soil tills easily, is well aerated, and has a high water infiltration rate. Increased levels of organic matter also influence soil humus.
The substance that results as the end product of the decay of plant and animal materials in the soil--provides a wide range of benefits to crop production. Sod-forming grass or grass-legume mixtures are important in crop rotations because they help replenish organic matter lost during annual cultivation. However, several years of sod production are sometimes required before measurable changes in humus levels occur. In comparison, annual green manures have a negligible effect on humus levels, because tillage and cultivation are conducted each year. They do replenish the supply of active, rapidly decomposing organic matter.
This was only a small part of the vast amount of wonderfully helpful knowledge this article presents about cover crops.
You can also visit the ATTRA website by going to www.attra.ncat.org. Happy Gardening!