Cover Crops for the Columbia Basin
Your Main Purpose for Using a Cover Crop |
Species Ranking for the Columbia Basin |
Legume N Source |
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N Scavenger |
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Build Soil Quality |
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Erosion Control |
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Loosen Sub-soil |
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Suppress Weeds |
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Suppress disease/nematodes |
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Grazing |
WINTER ANNUALS
Cereal Grains and Grasses
Columbia Basin farmers have used cereal grains as cover crops for many years because their ability to grow in cool temperatures. Winter wheat or triticale can be planted after late harvested crops and provide some cover through the winter. Cereal rye, although widely used in other regions of the country, is not used in the Columbia Basin because of its hard seed characteristics and the problems that creates when growing other cereal grains for seed.
When well established, cereal grains can provide good erosion control, capture residual nitrogen, and provide significant amounts of organic matter to the soil, which helps aggregate formation. They can also suppress weeds and provide grazing for livestock.
Winter Wheat and Triticale for Contract Grazing Fact Sheet
Annual ryegrass can also be used for a winter cover crop. It grows very quickly, provides excellent soil protection against erosion, and builds soil tilth through its dense root system and high biomass production. When mixed with legumes it establishes quickly and provides early weed control. It may not survive harsh winters in the Columbia Basin, but even then provides a good mulch for spring no-till plantings.
Annual Ryegrass Fact sheet (OSU)
Legumes
Columbia Basin farmers can use legume cover crops to fix atmospheric nitrogen for use by following crops, control erosion, add organic matter to the soil, and to attract beneficial insects. Hairy vetch and crimson clover are the two legume cover crops best adapted to our climate.
Hairy vetch has a long history of cover crop use. It is normally fall planted, but may be spring planted preceding late-planted summer crops. In the fall, the vetch will grow slowly, becoming established but not providing much soil cover. For this reason, hairy vetch is often planted with oats, which will winterkill, or winter wheat.
In the spring, fall-planted hairy vetch will grow quickly and has the ability to fix up to 200 pounds of nitrogen per acre. Because it has a high nitrogen content, hairy vetch residues will break down more quickly than grass or cereal residues. This means that the soil organic matter will not be built more slowly with hairy vetch or other legumes but neither will turning under a hairy vetch crop cause nitrogen immobilization.
Crimson clover can often survive our winters, but hairy vetch is a better choice for an overwintering legume cover crop. The advantage of using crimson clover is its rapid fall growth, which provides more weed suppressing, soil protecting cover than hairy vetch. Winterkilled crimson clover provides a good mulch for direct seeding, but spring killed plantings may be hindered by crimson clovers large stems. Its potential nitrogen fixing ability is slightly less than that of hairy vetch, but provides a better forage crop for livestock.
Crimson Clover Fact Sheet (OSU)
Brassicas
Several types of Brassica cover crops could be grown in the Columbia Basin, but due to the cross pollenization potential with the many Brassica-seed crops grown in the region, only Mustard is recommended. Recently, farmers have started using mustard (either white mustard, also known as yellow mustard, or oriental mustard ) for its biofumigation properties preceding potatoes. However, mustard can provide many other benefits including erosion control, soil improvement, and nutrient scavenging. It will normally winterkill in our climate, but farmers usually incorporate it in late October or early November, before it freezes.
SUMMER ANNUALS
Sudangrass and Sorghum-sudangrass hybrids
Farmers in the Columbia Basin have been using Sudangrass and sorghum-sudangrass hybrid cover crops for over ten years. They plant the grass in the summer before they plant potatoes, often after green peas, and incorporate it green before the first frost. The main benefit for potato farmers is suppression of verticillium, but there are also indications that some nematodes may be suppressed. Sudangrass cover crops can also provide large amount of biomass for soil building, provide some erosion control, and if mowed at the proper stage, can reduce sub-soil compaction.
Buckwheat
A cover crop of buckwheat provides nectar for beneficial insects and quick soil cover which will suppress weeds. It will also loosen the soil and scavenge phosphorus from the soil for use by the following crop. A crop of buckwheat will reach maturity in just 70-90 days. When it is turned under, it will break down quickly. Farmers use it as a quick, weed-smothering crop to control Canada thistle, sowthistle, creeping jenny, leafy spurge, Russian knapweed, and perennial peppergrass.
Buckwheat Fact Sheet (OSU)
Others to be added at a later date…
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