 |
| OSU HOME | EXTENSION HOME | ONLINE CATALOG | ORDERING INFORMATION |
| Extension Service |
Oregon Cover Crops: Red Clover(Trifolium pratense)EM 8701 Do you want to print a copy? We recommend downloading the print version (66 K). First download the free Adobe Reader, if you don't already have it. ContentsQuick facts Red clover is an herbaceous perennial or biennial legume with erect, leafy stems that originate from a thick crown andterminate with a flower head. Height at maturity is about 2 feet. Leaves are composed of three oblong leaflets that usually have light-colored "V" markings at their center. Both leaves and stems usually are hairy. Flowers are pink-purple or magenta. Seeds are small (approximately 240,000 seeds/lb), oblong, and yellow, reddish-brown, or dark gray. Red clover has a branched taproot and extensive surface roots. When used in annual rotations, fall and winter growth is slow, but spring growth is rapid. Environmental preferences and limitationsRed clover grows well on loams, silt loams, and sandy loams as well as on clayey soils. It can survive winter temperatures as low as -30°F and tolerates temporary waterlogging, but cannot survive prolonged waterlogging or flooding. The optimum pH range is 6.6-7.6, but a range of 4.5-8.2 is tolerated. UsesRed clover is used successfully in Oregon as a fall-planted cover crop and green manure in rotations with vegetable crops. It also is used as a relay interplanted cover crop (i.e., planted into a standing crop) and makes excellent forage, hay, and silage, although it should not be used as sheep pasture during breeding season because its high concentrations of estrogen-like compounds may cause infertility. Red clover residues can supply significant amounts of nitrogen (N) to subsequent crops, and the large, deep taproot is effective for loosening soils and cycling nutrients to the surface. Vigorous spring growth is effective for suppressing weeds. Dry matter and N accumulationIn a 5-year trial in the mid-Willamette Valley, 'Kenland'
red clover planted in mid-September accumulated a maximum of
3.3, minimum of 0.2, and mean of 1.7 tons dry matter/acre, and
a maximum of 168, minimum of 10, and mean of 83 lb
ManagementSuggested fall planting dates are from mid-September through early October, or earlier if irrigation is available or soils are moist. Seeding rates for use as a cover crop vary from 15 to 25 lb/acre. Drill seed into a fine seedbed at a depth of 1/2 inch for best stand establishment. Alternative seeding methods that can reduce seedbed preparation but require higher seeding rates are: drill into a rough seedbed prepared by disking, or broadcast over a rough or smooth seedbed and then disk lightly to cover seed. Red clover roots need to be colonized by an appropriate strain of rhizobia bacteria to be able to convert atmospheric nitrogen into plant-available forms. Inoculating seed with the proper rhizobia bacteria ensures that the bacteria will be present when the seed germinates. Use fresh inoculant, protect it from heat and light, and apply it to seeds just before planting according to the manufacturer's directions. Cover broadcast seed with soil to protect inoculant from sunlight. You may not need to inoculate if the appropriate rhizobia bacteria already are present in the soil. You can find out by planting a section of the field with raw (non-inoculated) seed and watching for differences in growth. When relay interplanting, broadcast seed into a standing vegetable crop before the final cultivation. Increase irrigation frequency to keep the soil surface moist until the clover is established under the summer crop canopy (about 2 weeks). Red clover has performed well when relay interplanted
into short-statured crops. When relay inter-planted into tall-statured
crops such as sweet corn, intense shade, heavy harvest residue,
and harvest traffic result in patchy stands. However, red In western Oregon, red clover generally is allowed to grow until at least mid-April, because nearly all dry matter and N accumulation occur in spring with the onset of warm weather. Incorporating red clover residues approximately 3 weeks before the summer crop is planted maximizes red clover spring growth while minimizing pythium problems (see below). When grown alone, red clover's succulent residues are incorporated easily with a moldboard plow or disk and decompose very rapidly, releasing part of the accumulated N for use by the following crop. Red clover often is planted with a cereal grain companion
crop that is able to scavenge N and protect the soil during fall
and winter. Plant companion crops at approximately one-half,
and clover at two-thirds, of their monoculture seeding rate. Red clover can be killed with an appropriate herbicide. Consult your county agent of the OSU Extension Service for herbicide recommendations. Follow all label restrictions.
Pest interactionsRed clover is not an appropriate cover crop to grow in rotation with a cash crop legume because they are susceptible to many of the same pathogens, allowing pathogen populations to grow quickly. Incorporation of succulent red clover residues often causes a sharp increase in soil-borne pathogen populations, especially damping-off fungi (e.g., pythium). If susceptible seed is planted shortly after incorporation, you may have more problems with disease. Avoid this problem by waiting several weeks between residue incorporation and planting, and by ensuring that soil temperature and seedbed preparation are optimal for rapid summer crop seedling emergence. Varieties/cultivarsCultivated red clovers are grouped as early flowering or late flowering types. 'Mammoth Red' is one of the most common late flowering, or single cut, varieties, and is used at high elevations or where the growing season is short. It is a winter-hardy biennial that grows in a round clump without flowering stems the first year. The early flowering types, also called 'Medium Red' or double cut (because they can be cut several times in a year for hay), comprise the majority of red clovers sown in Oregon. They produce tall, erect flowering stems with leaves at the nodes, the spring after they are planted. Although they are perennials, early flowering red clovers most often are treated as winter annuals (turned under or killed in spring) when used as a cover crop. Seed often is marketed simply as "Medium Red clover" and, if locally produced, may be well adapted. 'Kenland' red clover has been used successfully in the
Willamette Valley as both a fall-planted and relay-interplanted
cover crop. It is resistant to Sclerotinia crown rot and is tolerant
of waterlogged soils. 'Kenland' red clover is nearly dormant Prepared by Robert Sattell, faculty research assistant in crop and soil science; Richard Dick, professor of soil science; Delbert Hemphill, professor of agriculture; and Dan McGrath, Extension agent, Willamette Valley; Oregon State University. January 1998. |
|||||||||||||||||||||||||||||
|
Produced and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties. Oregon State University Extension Service offers educational programs, activities, and materials without discrimination based on age, color, disability, gender identity or expression, marital status, national origin, race, religion, sex, sexual orientation, or veteran's status. Oregon State University Extension Service is an Equal Opportunity Employer. Copyright © 1995- Oregon State University. Disclaimer. |