Adapted from: Clark, A. (ed.) 2007. Managing cover crops profitably. 3rd ed. SARE Outreach Handbook Series Book 9. National Agricultural Laboratory, Beltsville, MD. (Available online at: http://www.sare.org/publications/covercrops.htm) (verified 24 March 2010). Note: For this article, all information from the source that does not comply with organic certification regulations has been removed.
Also called: rye, winter rye, grain rye
Type: cool season annual cereal grain
Roles: scavenge excess N, prevent erosion, add organic matter, suppress weeds
Mix with: legumes, grasses or other cereal grains
The hardiest of cereals, rye can be seeded later in fall than other cover crops and still provide considerable dry matter, an extensive soil-holding root system, significant reduction of nitrate leaching, and exceptional weed suppression. Inexpensive and easy to establish, rye outperforms all other cover crops on infertile, sandy, or acidic soil, or on poorly prepared land. It is widely adapted, but grows best in cool, temperate zones. Taller and quicker-growing than wheat, rye can serve as a windbreak and trap snow or hold rainfall over winter. It overseeds readily into many high-value and agronomic crops and resumes growth quickly in spring, allowing timely killing by rolling or mowing. Pair rye with a winter annual legume such as hairy vetch to offset rye’s tendency to tie up soil nitrogen in spring.
Rye is the best cool-season cereal cover for absorbing unused soil N. It has no taproot, but rye’s quick-growing, fibrous root system can take up and hold as much as 100 lb N/ac until spring, with 25 to 50 lb N/ac more typical (UC SAREP Cover Crop Resource Page). Early seeding is better than late seeding for scavenging N (Brinsfield and Staver, 1991).
Figure 1. Hairy vetch plus winter rye were broadcast into this field of bell peppers at the end of August in southern Vermont. By late September the peppers have been damaged by frost but the cover crop is well-established to protect the soil over winter and fix nitrogen next spring for a subsequent crop. Photo and caption credit: Vern Grubinger, University of Vermont Extension.
In most regions, rye can serve as an overwintering cover crop after corn, or before or after soybeans, fruits, or vegetables. It’s not the best choice before a small grain crop such as wheat or barley unless you can kill rye reliably and completely, as volunteer rye seed would lower the value of other grains. Rye also works well as a strip cover crop and windbreak within vegetables or fruit crops and as a quick cover for rotation gaps or if another crop fails. You can overseed rye into vegetables and tasseling or silking corn with consistently good results. You also can overseed rye into brassicas (Schonbeck and DeGregorio, 1990; UC SAREP Cover Crop Resource Page), into soybeans just before leaf drop, or between pecan tree rows (Bugg, 1995).
An excellent source of residue in no-till and minimum-tillage systems, and as a straw source, rye provides up to 10,000 pounds of dry matter per acre, with 3,000 to 4,000 pounds typical in the Northeast (Duiker and Curran, 2005; Sarrantonio, 1994). A rye cover crop might yield too much residue, depending on your tillage system, so be sure your planting regime for subsequent crops can handle this. Rye overseeded into cabbage August 26 covered nearly 80 percent of the between-row plots by mid-October and, despite some summer heat, already had accumulated nearly half a ton of biomass per acre in a NewYork study. By the May 19 plowdown, rye provided 2.5 tons of dry matter per acre and had accumulated 80 lb. N/A. Cabbage yields weren’t affected, so competition wasn’t a problem (Porter, 1994).
Rye is one of the best cool season cover crops for outcompeting weeds, especially small-seeded, light-sensitive annuals such as lambsquarters, redroot pigweed, velvetleaf, chickweed, and foxtail. Rye also suppresses many weeds allelopathically (as a natural herbicide), including dandelions and Canada thistle, and has been shown to inhibit germination of some triazine-resistant weeds (Przepiorkowski and Gorski, 1994). Rye reduced total weed density an average of 78 percent when rye residue covered more than 90 percent of soil in a Maryland no-till study (Teasdale et al., 1991), and by 99 percent in a California study (UC SAREP Cover Crop Resource Page).
You can increase rye’s weed-suppressing effect before no-till corn by planting rye with an annual legume such as hairy vetch. Don’t expect complete weed control, however. You’ll probably need complementary weed management measures. Thick stands ensure excellent weed suppression. To extend rye’s weed-management benefits, you can allow its allelopathic effects to persist longer by leaving killed residue on the surface rather than incorporating it. Allelopathic effects usually taper off after about 30 days.
After killing rye, it’s best to wait three to four weeks before planting small-seeded crops such as carrots or onions. If strip tilling vegetables into rye, be aware that rye seedlings have more allelopathic compounds than more mature rye residue. Transplanted vegetables, such as tomatoes, and larger-seeded species, especially legumes, are less susceptible to rye’s allelopathic effects (Doll and Bauer, 1991). In an Ohio study, use of a mechanical under-cutter to sever roots when rye was at mid- to late bloom—and leaving residue intact on the soil surface (as whole plants)—increased weed suppression, compared with incorporation or mowing. The broadleaf weed reduction was comparable to that seen when sickle-bar mowing, and better than flail-mowing or conventional tillage (Creamer et al., 1995).
If weed suppression is an important objective when planting a rye–legume mixture, plant early enough for the legume to establish well. Otherwise, you’re probably better off with a pure stand. Overseeding may not be cost-effective before a crop such as field corn, however. A mix of rye and bigflower vetch (a quick-establishing, self-seeding, winter-annual legume that flowers and matures weeks ahead of hairy vetch) can suppress weeds significantly more than rye alone, while also allowing higher N accumulations.
While rye is susceptible to the same insects that attack other cereals, serious infestations are rare. Rye reduces insect pest problems in rotations (Wingard, 1996) and attracts significant numbers of beneficials such as lady beetles (Bugg et al., 1990).
Fewer diseases affect rye than other cereals. Rye can help reduce root-knot nematodes and other harmful nematodes, research in the South suggests (Barker, 1996; Wingard, 1996). Rye can reduce insect pest problems in crop rotations, southern research suggests (Wingard 1996). In a number of mid-Atlantic locations, Colorado potato beetles have been virtually absent in tomatoes no-till transplanted into a mix of rye–vetch–crimson clover, perhaps because the beetles can’t navigate through the residue.
If livestock are part of the operation, rye can provide early spring forage, before cool or warm season grasses are available for grazing. Rye fields provide forage for pastured pork or poultry, as well as ruminants. Livestock can utilize the nutrients, deposit manure, and help prepare the field for subsequent plantings.
Sow rye with legumes or other grasses in the fall or overseed a legume into rye in the spring. A legume helps offset rye’s tendency to tie up nitrogen. A legume–rye mixture adjusts to residual soil N levels. If there’s plenty of N, rye tends to do better; if there is insufficient N, the legume component grows better, Maryland research shows (Clark et al., 2007b). Hairy vetch and rye are a popular mix, allowing an N credit before corn of 50 to 100 lb. N/A. Rye also helps protect the less hardy vetch seedlings through winter.
Rye prefers light loams or sandy soils and will germinate even in fairly dry soil. It also will grow in heavy clays and poorly drained soils, and many cultivars tolerate waterlogging (Bugg et al., 1996). Rye can establish in very cool weather. It will germinate at temperatures as low as 34°F. Vegetative growth requires 38° F or higher (Sarrantonio, 1994).
Seed from late summer to midfall in Hardiness Zones 3 to 7 and from fall to midwinter in Zones 8 and warmer. In the Upper Midwest and cool New England states, seed two to eight weeks earlier than a wheat or rye grain crop to ensure maximum fall, winter and spring growth. Elsewhere, your tillage system and the amount of fall growth you prefer will help determine planting date. Early planting increases the amount of N taken up before winter, but can make field management (especially killing the cover crop and tillage) more difficult in spring. Rye is more sensitive to seeding depth than other cereals, so plant no deeper than 2 inches (Macey, 1992). Drill 60 to 120 lb./A (1 to 2 bushels) into a prepared seedbed or broadcast 90 to 160 lb./A (1.5 to 3 bushels) and disk lightly or cultipack (Sarrantonio, 1994; UC SAREP Cover Crop Resource Page). If broadcasting late in fall and your scale and budget allow, you can increase the seeding rate to as high as 300 or 350 lb./A (about 6 bushels) to ensure an adequate stand. Rye can be overseed by air more consistently than many other cover crops. “I use a Buffalo Rolling Stalk Chopper to help shake rye seeds down to the soil surface,” says Steve Groff, a Holtwood, PA, vegetable grower. “It’s a very consistent, fast and economical way to establish rye in fall.” (Groff’s farming system is described in detail at the Cedar Meadow Farm website).
Plant rye at the lowest locally recommended rate when seeding with a legume (Sarrantonio, 1994), and at low to medium rates with other grasses. In a Maryland study, a mix of 42 pounds of rye and 19 pounds of hairy vetch per acre was the optimum fall seeding rate before no-till corn on a silt loam soil (Clark et al., 1994). If planting with clovers, seed rye at a slightly higher rate, about 56 lb. per acre. For transplanting tomatoes into hilly, erosion-prone soil, Steve Groff fall-seeds per-acre mix of 30 pounds rye, 25 pounds hairy vetch and 10 pounds crimson clover. He likes how the three-way mix guarantees biomass, builds soil and provides nitrogen.
Although it’s not a common practice, you can spring seed cereals such as rye as a weed-suppressing companion, relay crop or early forage. Because it won’t have a chance to vernalize (be exposed to extended cold after germination), the rye can’t set seed and dies on its own within a few months in many areas. This provides good weed control in asparagus, says Richard deWilde, Viroqua, WI. After drilling a large-seeded summer crop such as soybeans, try broadcasting rye. The cover grows well if it’s a cool spring, and the summer crop takes off as the temperature warms up. Secondary tillage would be necessary to keep the rye in check and to limit the cover crop’s use of soil moisture.
Rye grows and matures rapidly in spring, but its maturity date varies depending on soil moisture and temperature. Tall and stemmy, rye immobilizes nitrogen as it decomposes. The nitrogben tie-up varies directly with the maturity of the rye. Mineralization of nitrogen is very slow, so don’t count on rye’s overwintered nitrogen becoming available quickly. Killing rye early, while it’s still succulent, is one way to minimize nitrogen tie-up and conserve soil moisture. But spring rains can be problematic with rye, especially before a N-demanding crop, such as corn. Even if plentiful moisture hastens the optimal kill period, you still might get too much rain in the following weeks and have significant nitrate leaching, a Maryland study showed (Decker et al., 1992). Soil compaction also could be a problem if you’re mowing rye with heavy equipment on wet soils.
Late killing of rye can deplete soil moisture and could produce more residue than your tillage system can handle. For no-till corn in humid climates, however, summer soil-water conservation by cover crop residues often was more important than spring moisture depletion by growing cover crops, Maryland studies showed (Clark et al., 1995; Clark et al., 1997; Clark et al., 2007a).
One way to offset yield reductions from rye’s immobilization of nitrogen would be to increase your N application. Here’s another option: Growing rye with a legume allows you to delay killing the covers by a few weeks and sustain yields, especially if the legume is at least half the mix. This gives the legume more time to fix N (in some cases doubling the N contribution) and rye more time to scavenge a little more leachable N. Base the kill date on your area’s normal kill date for a pure stand of the legume (Decker et al., 1992). A legume–rye mix generally increases total dry matter, compared with a pure rye stand. The higher residue level can conserve soil moisture. For best results, wait about 10 days after killing the covers before planting a crop. This ensures adequate soil warming, dry enough conditions for planter coulters to cut cleanly, and minimizes allelopathic effects from rye residue (Clark et al., 1997; Decker et al., 1992). Legume–rye mixes can be rolled once the legume is at full bloom.
Tilling under rye usually eliminates regrowth, unless the rye is less than 12 inches tall (Sarrantonio, 1994; UC SAREP Cover Crop Resource Page). Rye often is plowed or disked in the Midwest when it’s about 20 inches tall (Oekle et al., 1990). Incorporating the rye before it’s 18 inches high could decrease tie-up of soil N (Sarrantonio, 1994; UC SAREP Cover CropsResource Page). In Pennsylvania (Duiker and Curran, 2005) and elsewhere, kill at least 10 days before planting corn. For best results when mow-killing rye, wait until it has begun flowering. A long-day plant, rye is encouraged to flower by 14 hours of daylight and a temperature of at least 40°F. Mow-kill works well in the South after rye sheds pollen in late April (Dabney, 1996). If soil moisture is adequate, you can plant cotton three to five days after mowing rye when row cleaners are used in reduced-tillage systems. Some farmers prefer to chop or mow rye by late boot stage, before it heads or flowers. “If rye gets away from you, you’d be better off baling it or harvesting it for seed,” cautions southern Illinois organic grain farmer Jack Erisman (Bowman, 1997). He often overwinters cattle in rye fields that precede soybeans. But he prefers that soil temperature be at least 60°F before planting beans, which is too late for him to no-till beans into standing rye. “If rye is at least 24 inches tall, I control it with a rolling stalk chopper that thoroughly flattens and crimps the rye stems,” says Pennsylvania vegetable grower Steve Groff. A heavy duty rotavator set to only 2 inches deep does a good job of tilling rye, says Richard de Wilde, Viroqua, WI. Can’t delay a summer planting by a few weeks while waiting for rye to flower? If early rye cultivars aren’t available in your area and you’re in Zone 5 or colder, you could plow the rye and use secondary tillage. Rye is the best cool-season cover crop for scavenging N, typically carrying 25 to 50 lb N/ac over to spring.
Talk to farmers across America about cover crops and you’ll find that most of them have planted a cereal rye cover crop. Almost certainly the most commonly planted cover crop, cereal rye can now be seen growing on millions of acres of farmland each year. There are almost as many ways to manage cover crop rye as there are farmers using it. Climate, production system, soil type, equipment, and labor are the principal factors that will determine how you manage rye. Your own practical experience will ultimately determine what works best for you. Test alternative management practices that allow you to seed earlier or manage cover crop residue differently. Add a legume, a brassica or another grass to increase diversity on your farm.
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