A Guide to Planting Spring Cover Crops
Planting cover crops is a powerful way to improve your soil. Cover crops perform a host of valuable functions like increasing soil organic matter, fixing nitrogen, breaking up compaction, suppressing weeds and preventing erosion. In this guide we'll discuss your options for spring cover crops and the benefits of each, when and how to plant, and how to manage the crop once it's established.
While commercial growers typically use a seed drill or mechanical broadcaster to plant cover crops (followed by mowing and tilling before the crop sets seed), home gardeners can grow cover crops too. For gardeners we recommend planting most cover crops by hand-broadcasting seed over freshly turned soil, then raking in lightly just before a rain. When the cover crop is in flower, just before it sets seed, it should be cut with a scythe or mower, then left as a living mulch for the rest of the season or turned under with a rototiller. Because of the nutrients bound up by the decomposing crop, it is recommended to wait 2-3 weeks after tilling before planting another crop into the area. At this point the cover crop residues will have mostly decomposed, making organic matter and nutrients available to the next crop.
BMR Sorghum-Sudangrass F1
Life cycle: Annual
Benefits: fast growing, tolerates drought, builds biomass, smothers and discourages weeds, penetrates compact soil. Can grow to 12’ tall with 4,000-5,000 lbs of dry matter produced per acre, easier to grow than corn (for silage)
Uses: soil building, silage or green forage when 24-30” tall (not suitable for horses)
When to sow: Late May to early July depending on location, or when soil reaches 60ºF
Days to maturity: 90-100
Seeding rate and depth: 35 lbs/acre drilled or 40-50 lbs/acre broadcast, .5” deep in heavy soil, 1.5” deep in sandy soil
How to harvest: Mow when crop reaches 36-40” tall for silage
Limitations: soil temperature must reach 65ºF at least two months before first fall frost. Performs poorly in waterlogged soils
Learn more about Sorghum-Sudangrass for silage here
Common Buckwheat
Life cycle: Annual
Benefits: a rapid grower widely used for smothering weeds, lightening heavy soils, holding nutrients for the next crop and attracting pollinators
Uses: as a green manure in rotation with vegetable crops, for grain
When to sow: late May through July or when soil is at least 50ºF, at least 3 months before first frost for grain
Days to maturity: 35-42 bloom, 70-84 grain
Seeding rate and depth: 2-3 lbs/1000 sq ft or 35-135 lbs/acre
How to harvest: for green manure mow or harrow before seeds mature, about one month after planting. For grain cut when 80-90% of seeds have turned brown, after killing frost
Limitations: does not tolerate waterlogged soils or very hot, dry weather (later planting is recommended for Southern growers to avoid the hottest part of the summer)
Learn more about Buckwheat for grain production here
Medium Red Clover
Life cycle: Perennial
Benefits: fixes nitrogen, mines nutrients & conditions soil, tolerates shade, reduces compaction, attracts beneficial insects, tolerates poor/wet/acid soils, produces 2-4 tons dry matter/acre in 2nd year
Uses: soil builder, ground cover, undersown in existing crops, insectary, hay and forage
When to sow: Spring to summer when soil is above 41ºF
Days to maturity: 14 months when spring sown
Seeding rate and depth: Broadcast, drilled or frostseeded 1/2 lb/1,000 sq ft or 5-15 lbs/acre, ¼-1/2” deep
How to harvest: Incorporate once blooming begins in spring of 2nd year by mowing and/or tilling under
Limitations: not exceptionally heat-tolerant; growers in the South should plant in late summer/fall for overwintering
TIP: “Frostseeding” can be effective at least a month before last frost; sow in early morning when soil is still frost-covered
Field Peas
Life cycle: Annual
Benefits: fixes nitrogen, builds soil, moderate weed suppression, biomass decomposes quickly, edible tops
Uses: soil builder, edible tendrils, forage crop
When to sow: Early spring as soon as soil can be worked
Days to maturity: 52-75
Seeding rate and depth: 5 lbs/1,000 sq ft or 200 lbs/acre, 1 ½ to 3” deep
How to harvest: Till when flowering begins
Limitations: does not tolerate hot, dry conditions; growers in the South should use as fall/winter crop in areas where legumes have not been grown recently
TIP: Oats support weak pea stems and act as a “nurse” crop; sow 120 lbs of peas with 2 bushels of oats per acre
Improved White Clover
Life cycle: Perennial
Benefits: fixes nitrogen, reduces compaction, improves soil health, tolerates mowing/trampling/wet soils/drought
Uses: soil builder, excellent for paths and lawns, undersow around existing crops for living mulch, green manure, hay, pasture forage
When to sow: Anytime, preferably before a rain
Days to maturity: 60-70
Seeding rate and depth: ¼ lb/1,000 sq ft, 5-9 lbs/acre drilled, 7-14 lbs/acre broadcast then rolled, raked or cultivated to ensure good soil contact
How to harvest: Chisel or moldboard plow to kill; regular mowing to maintain
Limitations: Slow to establish, not ideal for smothering weeds.
TIP: Combine with Annual Ryegrass to increase soil benefits. “Frostseeding” can be effective a month before last frost; sow in early morning when soil is still frost-covered
Oats
Life cycle: Annual
Benefits: fast grower, prevents erosion, suppresses weeds, scavenges nutrients, builds biomass with up to 8,000 lbs/acre dry matter from spring stands
Uses: soil builder, nurse crop for legumes, green manure, grain, hay
When to sow: Early spring to summer, when soil is at least 38ºF
Days to maturity: 100-120 for grain
Seeding rate and depth: Broadcast or drill 4 lbs/1,000 sq ft or 100-140 lbs/acre 1” deep
How to harvest: Till in when seedheads are just forming, or cut grain when seeds harden
Limitations: performs poorly in hot, dry weather; Southern growers should plant in fall
Annual Ryegrass
Life cycle: Annual
Benefits: fast grower, suppresses weeds, controls erosion, adds organic matter, catches nutrients, thrives in all soil types
Uses: soil builder, nurse crop, emergency forage
When to sow: Anytime soil is at least 40ºF
Days to maturity: 50-70
Seeding rate and depth: Broadcast 20-30 lbs/acre or drill 10-20 lbs/acre ½” deep
How to harvest: Disk, till or plow under as soon as flowers form
Limitations: occasionally some plants overwinter and become weedy
Yellow Sweet Clover
Life cycle: Biennial
Benefits: nitrogen-fixer, mines nutrients from deep in soil, drought-tolerant, attracts beneficials, tolerates poor soil, adds up to 2.5 tons dry matter/acre in first year
Uses: excellent green manure, soil builder, subsoil aerator, and honey plant
When to sow: Spring to summer when soil is at least 42ºF
Days to maturity: 60-70 to bloom
Seeding rate and depth: Broadcast ½ lb/1,000 sq ft or 15-20 lbs/acre, drill 8-15 lbs/acre
How to harvest: Kill early in 2nd year by mowing or tilling when stalks are 6-10” tall
Limitations: does not tolerate waterlogged soil; recommended for fall in the South
TIP: Best grown with 2 bushels of oats as a nurse crop
Field Peas/Oats Mix
Life cycle: Annual
Benefits: versatile, fixes nitrogen, builds soil, suppresses weeds, decomposes quickly, edible pea tendrils
Uses: versatile soil builder, marketable pea tendrils, forage crop
When to sow: Early spring when soil is at least 38ºF
Days to maturity: varies
Seeding rate and depth: Broadcast 5 lbs/1,000 sq ft or 200 lbs/acre and rake or cultivate
How to harvest: till under or otherwise incorporate before seeds are set
Limitations: peas do not tolerate very hot dry weather; may be grown as a fall crop in the South
Field Peas/Oats/Vetch Mix
Life cycle: Annual
Benefits: versatile, fixes nitrogen, suppresses weeds, decomposes quickly, edible pea tendrils, adds up to 8,000 lbs/acre of organic matter
Uses: versatile green manure, soil builder, marketable pea tendrils, forage crop
When to sow: Early spring when soil is at least 38ºF
Days to maturity: varies
Seeding rate and depth: Broadcast 6-8 lbs/1,000 sq ft or 210 lbs/acre and rake in
How to harvest: till under or otherwise incorporate before seeds are set
Limitations: peas do not tolerate very hot dry weather; may be grown as a fall crop in the South
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