Cover Crop
Benefits
Crop
Yields Soil
Quality Beneficial
Insects Diseases
and Nematodes Weeds Nutrient
Availability Soil
Compaction Soil
Moisture Erosion Runoff Organic
Matter Infiltration
Cover Crops and Nutrient Availability
Nitrogen recycling
Nitrogen is the most
difficult nutrient to manage in agricultural systems. It is necessary
in large quantities for adequate crop growth and yield, but it is also
extremely mobile in soil. Planting a non-leguminous cover crop after main
crop harvest can "trap" leftover, residual soil nitrogen through
cover crop uptake. This reduces the potential for leaching losses through the winter months. Cover crops used in this way are sometimes
called catch or trap crops. Additionally, the cover crop utilizes excess
water in the soil, which also helps limit leaching. (From Summer
Cover Crops, N. G. Creamer and K. R. Baldwin, North Carolina State
University).
In the Columbia Basin, farmers (link to case studies) have used cereal grain cover crops like winter wheat and triticale to keep soil nitrogen from leaching during the winter. If planted early enough in the fall, they can take up and recycle over 100 lbs. of nitrogen per acre to the following summer crop. This is nitrogen that might otherwise contaminate groundwater in the future.
Leguminous cover crops, such as hairy vetch and crimson clover, can "fix" significant amounts of nitrogen for use by following crops. Through a symbiotic association with the legume, Rhizobium bacteria convert atmospheric nitrogen into a form that the legume can use for its own growth. When grass or legume cover crops are killed or incorporated, soil microorganisms decompose their residue. In a process called mineralization, the N in the plant tissue is converted by soil microbes into a form (nitrate) that subsequent plants can use.
Nitrogen in the aboveground biomass of the cover crops varies considerably within species, but legumes generally contribute anywhere from 60-200 lb of N per acre. This nitrogen is mineralized over an extended period of time, with an average of 50% of the total N contained in the cover crop available to subsequent crops. (From Summer Cover Crops, N. G. Creamer and K. R. Baldwin, North Carolina State University).
See also Nitrogen Fixation by Legumes, New Mexico State University.
Cover crops help recycle other nutrients on the farm. Besides nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), and other nutrients are all accumulated by cover crops during a growing season. When the green manure is incorporated, or laid down as mulch, these plant-essential nutrients become slowly available during decomposition.
Certain broad-leaved plants are noted for their ability to accumulate minerals at high concentrations in their tissue. For example, buckwheat, lupine, and sweetclover are noted for their ability to extract P from soils. Likewise, alfalfa and other deep-rooting green manures scavenge nutrients from the subsoil and move them upwards to the surface, where they become available to the following crop.
The breakdown of green manures in soils influences mineral nutrient availability in another way. During decomposition of organic matter, carbonic and other organic acids are formed. These organic acids react with insoluble mineral rocks and phosphate precipitates, releasing phosphates and exchangeable nutrients. (Adapted from Overview of Cover Crops and Green Manures, ATTRA).
Secondary content using h2 tag. Column 2
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
Heading using the h3tag
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.