sign in sign up
<<
Home , Millet, Pearl millet, Rye

Cover for All Seasons Expanding the cover tool box for organic producers Mark Schonbeck and Ron Morse Virginia Association for Biological Farming Information Sheet

Number 3-06 05/15/06 http://www.vabf.org/pubs.php Organic and gardeners have striven for decades to maximize the health of the they Contents: cultivate. Meanwhile, scientists have identifi ed three key factors in soil organic matter balance and Introduction p.1 soil quality: tillage, biomass input, and soil erosion. Descriptions of Individual Cover Crops p.1 They recommend: Contact Information p.3 • reduce intensity and frequency of tillage Table of Cover Crops p.4 • grow cover crops to: – maximize biomass on a number of cover crops, including hardiness, – optimize nitrogen (N) dynamics planting time rates and depths, maturity date, biomass – minimize bare-soil periods and other characteristics; and management methods. – eliminate erosion The following paragraphs on individual species are based partly on our observations and partly Studies have shown dramatic increases in active on decades of collective experience of growers and and total soil organic matter under continuous no-tillage researchers in the southern region. systems. Because these systems rely on herbicides to control competing vegetation during crop Winter ( rye) is the most often used winter production, they are not suitable for organic producers. cover crop. It produces lots of biomass, suppresses Organic agriculture has even been criticized from a weeds through competition and allelopathy (release soil-conservation standpoint for its heavy reliance on of natural substances that inhibit weed germination tillage and cultivation for weed control. However, and early growth), takes up and conserves soluble soil skillful use of cover crops adds considerable biomass N, and provides support for viny legumes like vetch. to the soil organic matter cycle and reduces the need for It tolerates somewhat acid or low-fertility soils, and tillage and cultivation. Some cover crops can be rolled, can be killed by mowing after full heading in late mowed or frost-killed to allow organic no-till planting, spring. Rye may tie up soil N if grown alone, and its while others require tillage or undercutting. The latter allelopathy can inhibit crop sown too soon after can sometimes be grown as a living mulch between it is tilled in. Wait 3-4 weeks. beds or rows of the production crop, thus continuing and also make good, hardy winter to contribute biomass and protect soil. Researchers at cover crops. Generally similar to rye, they mature a Virginia Tech and several VABF member growers are little later and may be harder to mow-kill. developing and testing cover-crop based conservation tillage systems for organic , including no- provides good biomass and weed till vegetable planting into mechanically killed cover suppression. It prefers light textured soils, fairly crops. deeply, and tolerates better than other small . One of the basic tenets of sustainable agriculture is that greater diversity yields greater agro-ecosystem Annual ryegrass (Italian ryegrass) can be grown stability, more benefi cial organisms, fewer pests as a winter or summer annual. Its dense fi brous and diseases, more sustained crop yields, and more system promotes crumb structure and stops soil opportunities for innovation. Thus one of erosion. It forms a lot of biomass, suppresses weeds our research goals is to develop a larger cover crop and conserves soil N. It cannot be mow-killed and must “toolbox” from which growers can select cover crops be tilled in as . Note: any sold as most suited to their regions and production systems. “annual rye” is ryegrass if it looks like lawn grass seed, The table on pages 4-6 gives some basic information and is winter rye if it looks like wheat berries. Cover Crops for All Seasons. Number 3-06 page 2

Hairy vetch is the best winter annual legume for Bell bean or fava bean is a good N fi xer, it also cooler regions in the South, surviving freezes to -10°F. provides abundant nectar for benefi cial insects, and It performs well on a wide range of soils, fi xes over is a good legume companion for spring . It does 100 lb N per acre, and releases about half of it to the not tolerate drought or heat, so late summer plantings following . Other vetches include lana vetch may not always thrive. Bell beans are smaller seeded (hardy to zone 7), and purple vetch (zone 8), which than horticultural favas and are better suited as cover give more biomass and N than hairy vetch from spring crops. plantings. Vetches make soil (P) more Daikon, oilseed and radishes are deep- available, and provide excellent habitat for benefi cial rooted, semi-hardy cover crops that open subsoil insects that eat or parasitize insect pests. hardpan, scavenge and conserve soluble soil N, and Bicultures (two-species combinations) of N-rich choke out weeds through rapid canopy closure and vetches with rye, barley or oats are often planted for strongly allelopathic root exudates. Fall-planted radish maximum cover and biomass, weed suppression, and decays rapidly after winterkilling, leaving a clean, benefi cial habitat. Their balanced carbon-to-nitrogen weed-free seedbed for spring vegetables. To avoid pest (C:N) ratio also maximizes soil organic matter and disease problems, radishes should not be grown formation and provides season-long, slow-release N. immediately before or after brassica vegetables. Crimson clover is the best winter annual legume is the most widely available and widely for mild temperate climates (zones 7-8). Known grown summer annual cover crop. Its short (30-45 day) for its spectacular bloom in the spring, it provides lifecycle, rapid canopy closure, and weed suppression valuable benefi cial habitat, weed suppression, good make it ideally suited for short fallow periods during biomass and nitrogen fi xation. Because of its lower N the frost-free season. Buckwheat makes soil P more content (about 2-2.5%, compared to 3-4% for vetches), available. It is also one of the best nectar sources for crimson clover residues release N more slowly than benefi cial insects. It likes warm weather and moist other winter legumes. It is easy to kill by mowing soil, and does not tolerate much drought. at full bloom and it self-seeds readily if allowed to Sudangrass and -sudan hybrids produce stand more than a few days past peak bloom. Caution: tremendous biomass, reaching nine feet within two crimson clover may support pest nematodes that can to three months. Sorghum-sudan chokes out weeds affect tomato and some other vegetables, in regions through competition and strong allelopathy. When where these nematodes are prevalent. Other winter grown to about 5-6 feet, then mowed back to one annual clovers with good N fi xation potential include foot and allowed to regrow, sorghum-sudan sends its berseem clover, and subterranean clover. fi brous roots deep into the subsoil to break hardpan. It Austrian winter peas, hardy to zone 7, add a lot of tolerates heat and drought, but requires warm soil with biomass and N. Peas are viny and do best when grown ample N to thrive, and does well planted in alternate with a cereal for support. Several other varieties rows with a vigorous summer legume. Diffi cult to of fi eld peas are semi-hardy and can be planted in early mow-kill, this crop is best planted at midsummer and spring or late summer. In the latter case, they will allowed to winterkill ahead of spring vegetables. winterkill except in zones 8b or higher. Spring planted Various species of make good summer cover Austrian peas also perform well. crops with high heat and drought tolerance. Foxtail, Spring oats are semi-hardy, and are the best cool- proso and Japanese are best suited for early season grass to in early spring or late summer with summer (June) plantings, as later plantings produce cool season legumes. Like rye, oats suppress weeds, little biomass because of daylength responses. Foxtail tolerate a wide range of soils, form a lot of biomass and are easy to mow-kill, while Japanese and conserve soluble soil N. Oats are somewhat higher and browntop millet grow back readily. in N than rye and less likely to tie up soil N upon is very tall and rivals sorghum-sudan in late summer incorporation. Black is a close relative, grown in biomass production, yet is easy to kill by mowing or , and experimentally in the US. rolling. Millets do well with or . Cover Crops for All Seasons. Number 3-06 page 3

Cowpea is a versatile summer legume that fi xes lots of N, provides food and habitat for benefi cial insects, suppresses pest nematodes, rapidly shades out weeds, Contact Information: and offers edible shell beans (blackeyed peas, etc.). Virginia Association for Biological Farming Cowpeas are not bothered by Mexican bean , Post Offi ce Box 1003 Japanese beetles or deer, and are incredibly tolerant of Lexington, Virginia 24450 hot, dry conditions. They require warm soil to emerge well and are not easily killed by mowing. www.vabf.org

Soybean also makes an excellent summer legume Where to Get Cover Crop Seeds: cover crop. Late maturing or varieties should be grown to obtain ample top growth before they set seed SPECIAL NOTE FOR ORGANIC GROWERS: Be and die down. Soybeans are a little more cold-tolerant sure to buy or order seeds that have not been treated than and can produce more biomass and N, but with synthetic fungicides or pesticides - order early in the season while untreated seed is still available. are more susceptible to drought and pests. Local farm supply stores and Southern States stores Sunnhemp (crotolaria) is a tall, stemmy tropical usually carry rye, oats, various clovers, buckwheat, and legume that tolerates lower soil fertility, produces lots sometimes alfalfa, vetches, wheat, ryegrass, foxtail of biomass and chokes out weeds. Lablab bean is a millet, and cowpeas. Often they can special- viny tropical legume that appears to leave a strongly order some cover crop seeds. allelopathic (weed-suppressing) residue after frost-kill. Adams Briscoe Seed Company (GA), 770-775-7826, Both are experimental in our region. The seeds can be www.abseed.com. Sorghum-sudan hybrids; pearl, expensive and diffi cult to obtain. proso, foxtail, browntop and Japanese millets; cowpeas, high-biomass forage soybeans; lablab bean Yellow sweetclover is a very hardy biennial that and several other warm season legumes. can be planted in spring through late summer, then tilled or mow-killed early the following summer after Albert Lea Seed House (MN), 800-352-5247, www.alseed.com. All millets, sorghum, sudangrass fl owering. Sweetclover has strong deep taproots that and sorghum-sudan hybrids; rye, oats, wheat, barley can break hardpan and make soil P more available. and triticale; annual and perennial ryegrass and other Annual white sweetclover is semi-hardy. grasses; red, crimson, yellow sweet and other clovers and alfalfa; field peas, vetches and other legumes. Perennial clovers such as red, white and alsike Some organic seeds. clovers make good living mulches when overseeded into established cash crops, fi xing N and offering Peaceful Valley Farm Supply (CA), 888-784-1722, www.growingorganic.com. Several varieties of vetch, benefi cial habitat over winter and into the next season. field peas, bell beans, lablab, sunnhemp, other unusual Alfalfa, the “queen of ”, is drought tolerant legumes, cereal grains, annual and perennial grasses, and a superior N fi xer, but it requires quite fertile soil. and daikon radish. Most seeds are organic or free of synthetic chemical treatments. These legumes can also be grown with perennial grasses such as timothy, orchardgrass and perennial Plantation Seed, 800-543-4164. Black oats. ryegrass, for two to four years to give intensively Seven Springs Farm (VA), 540-651-3228, cultivated fi elds a good rest. Rotating to a grass- www.7springsfarm.com. Rye, , hairy legume sod can restore soil organic matter levels and vetch, Austrian winter field peas, crimson clover, reduce summer annual weeds. Perennial cover crops spring oats, spring barley and buckwheat. All seed untreated, most organic. start slowly and are often planted with a light sowing of spring oats to help them get started. The oats are Turner Seed (TX), 800.722.8616; mowed off at heading to allow the perennials to get www.turnerseed.com. Lablab bean, sunflower, forage established. turnip and a wide range of summer and winter annual grains, grasses, clovers and other legumes.

Cover Crops for All Seasons. Number 3-06 page 4 7 How to manage Mow Mow or Roll Mow SK Mow Till WK (zone 6) or Mow Mow Mow Roll? Mow, WK Mow, WK best; Mow? WK Roll or Mow, WK, Mow WK WK WK WK NR, P 6 SS W, P, TS P, W, B, P, TS, W TS, P, W TS, P, SS, P, , P, TS, W TS, , P, , N B, P, TS, W TS, B, P, NR,B,P,W*,TS TS B, , B, P, TS , B, P, W* , , N, NR, P, W , N, NR, P, Main ts benefi N, B B N, W*, N, B, N, B, WK (zone 6) or Mow N, N N, P, N, B, N, B, N, N, B, W N 5 tons/ac 1-3 1.5-3 1.5-3 1.5-4 1.5-4 2-4 1-2.5 1.5-4 1-2.5 1.5-4 1-3.5 2.5-4.5 1-2 Biomass,

4

Ht, ft v 3-5 2 v 3-5 1-2 v 3-5 2-3 v 3-5 2 v 3-6 2-4 2-4.5 v 2-5 5-7 v 5-10

3

Maturity May April late May late spring early June April WK or late April-May June-July WK or 55-70 DAP July? WK June WK June WK or 60-70 DAP 50-75 DAP 50-90 DAP V or 90 DAP V F F 2 ° ° 65 65 ≥ ≥ When to plant early fall late summer late summer late summer early spring late summer mid- late summer early spring late summer early spring late summer early spring late summer early spring late summer after frost when soil after frost when soil

Seed inoculant pea/vetch clover pea/vetch clover pea/vetch clover pea/vetch lupine pea/vetch pea/vetch soybean cowpea cowpea lablab in. 1⁄2-11⁄2 1⁄4-1⁄2 1-3 1⁄4-1⁄2 1⁄2-1 1⁄4-1⁄2 1-3 3⁄4-1 1⁄2-1 1-3 1-2 3⁄4-11⁄2 1⁄2 -1 1-1 1⁄2 Depth, 1 lb/ac 20-40 15-30 70-120 10-30 20-60 8-20 70-120 70-120 30-80 80-150 60-120 50-100 30--50 10-50 °F -10 0-10 0-10 0-15 0-15 5-20 10-20 15-20 20 20 tender tender tender tender Hairy vetch Crimson clover Subclovers Lana vetch Berseem clover Field peas Lupine Purple vetch Bell / fava bean Soybean Cowpeas Sunnhemp Lablab bean Aus. winter peas Crop Hardiness, Seeding, Crop Species Annual Legumes: Cover Crops for All Seasons. Number 3-06 page 5 7

How to manage Mow or Roll Mow? Mow? Mow/Roll at stage Mow/Roll at milk stage Mow/Roll at milk stage Roll? Mow, Mow Mow or Roll WK best, Mow? or Mow or Roll WK Roll or Mow, WK or Till WK or Till Till (WK zone 5-6) Till WK WK WK WK Till B,TS TS K,TS,B TS, B NR, B 6 TS , TS , NR, B, TS NR, B, NR, B, TS NR, B, , TS, K Till Till TS, K , NR NR, TS NR, W*, P, W*, P, NR, TS NR, , NR, TS , NR, , , Main ts benefi W*, NR, TS NR, K, W, TS NR, K, W, W*, W* W*, W*, NR, NR, W, W*, NR, SS, B W*, SS, W W W, W, 5 tons/ac 2-5 1.5-3.5 2-4 1.5-5 2-3 1.5-4 1.5-4 1.5-3 1.5-3 1-1.5 3-6 1.5-3.5 3-5 2-4 3 Biomass, 4 Ht, ft 4-6 3-4 3-5 2-3 3 2-3 3 3 1.5-3 2-3.5 7-9 3-4 6-8 4-6 3

3

Maturity May late May late May April late Summer Spring early June WK or 60 DAP June WK or 70 DAP June-July WK June WK Oct. or 65-75 DAP 60 DAP 65-70 DAP 50 DAP 45 DAP

F 2 ° 70 ≥ When to plant fall fall fall early fall early spring late summer early spring late summer early spring late summer early spring late summer early spring late summer after frost –late sum.30 DAP when soil after frost – June August June – after frost – June after frost

Seed inoculant

in. 3⁄4-2 1⁄2-11⁄2 1⁄2-11⁄2 3⁄4-2 1⁄4-1⁄2 3⁄4-2 1⁄2-2 1⁄2 1⁄2 1⁄2-11⁄2 1⁄2-11⁄2 1⁄4-1⁄2 1⁄4-1⁄2 1⁄2-1 1⁄4-1⁄2 Depth, 1 lb/ac 60-150 60-120 60-120 50-125 15-30 50-125 80-140 15-50 10-20 60-80 25-50 20-35 10-30 20-30 20-30

°F -40 -25 <-10 0 l0-10 15 15-20 20 20 tender tender tender tender tender tender

Ryegrass, ann. Ryegrass, Spring Barley Spring oats Black oats Radish (daikon, oil or fodder) Buckwheat Sorghum-sudan Pearl millet Japanese millet Browntop millet Winter rye Winter wheat Winter Triticale Barley Winter Crop Hardiness, Seeding, Crop Species Annual Non-Legumes: Crop Hardiness, Seeding, Depth, Seed Ht, Biomass, Main Cover Crops for Number3-06 Seasons. All Species °F lb/ac1 in. inoculant When to plant2 Maturity3 ft4 tons/ac5 benefi ts6 How to manage7 Biennials and Perennials: Sweetclover < 0 12-20 1⁄4-1⁄2 alfalfa spring or late sum. late 2nd spring 3-6 1.5-3 SS,P,N,B,W,NR Mow Red clover < 0 10-15 1⁄4-1⁄2 clover spring or late sum. 2nd season 2-3 N, P, SS, B, W Till White clover < 0 5-15 1⁄4-1⁄2 clover spring or late sum. 2nd season 0.5-1.5 B, N, P Till Alfalfa, dormant < 0 20-25 1⁄4-1⁄2 alfalfa spring or late sum. 2nd season 1.5-2 N, SS, B, W, NR Till Orchardgrass < 0 15-20 1⁄4-1⁄2 spring or early fall 2nd season 4-5 TS, W, K, B Till Timothy < 0 12-15 1⁄4-1⁄2 spring or early fall 2nd season 2-3.5 TS, W, K, B Till

Ryegrass, peren. 0 25-35 1⁄4-1⁄2 spring or early fall 2nd season 3-4 TS, NR, W, K, B Till

1 Lower rates for drilling, higher rates for broadcast seeding. For grass + legume biculture, sow grass at lower rates, legume at medium rates. 2 after frost = spring frost-free date until midsummer; late summer = ~6-8 weeks before fall frost; 3 Full bloom or full head, days after planting (DAP), or month of full bloom in Appalachian region of Virginia. V = remains vegetative; WK = winterkills. 4 At full bloom or full head. A “v” indicates crop is a vine; number gives typical vine length. Unsupported vines generally form mat 1-2 ft thick. 5 Estimated aboveground biomass for cover crop grown until full bloom, immature seed stage, or winterkill in Zones 6a-8b of southeastern US, including VA, NC, SC, KY, TN, GA, AL. Total biomass including roots + exudates is about 50% more. Biomass for grass + legume covers may exceed either one grown alone. 6 B = harbors benefi cial insects; N = fi xes nitrogen; NR = takes up and holds soluble soil N; P = makes soil phosphorus more available; K = makes soil potassium more available; W = suppresses weeds; SS = opens subsoil; TS = conditions/mellows topsoil. All cover crops add organic matter and protect soil from erosion. = particularly strong effect. W* indicates allelopathic effect – residues can inhibit emerging cash crop, effect

Boldface page6 subsides in a few weeks or over winter. 7 Till = requires tillage. Mow, Roll = mow or roll at or after full bloom for no-till; WK = allow to winterkill; SK = self seeds and dies in late spring, seeds germinate at end of summer. All cover crops can be managed by tilling in at any time before mature seed forms. Mow heavy top growth a week before tilling.