Cover Crop Species Guide

Comprehensive reference for cover crop species used in no-till and conservation agriculture systems. Based on Frédéric Thomas and Matthieu Archambeaud’s guide published in TCS Magazine (France) and reproduced in Direct Driller Issue 2.

“During the period between cash crops, seeding any cover-crop is a big step forward in restoring water quality, maintaining and developing soil fertility and in the long term saving fertiliser inputs and reducing the need for tillage. There is no such thing as a bad species and neither are there any specifically good ones.”

Basic Arable Species

Species Seeding rate (kg/ha) Notes
Common (white) mustard 10 single; 3–4 in mix Cheap, fast-establishing; fibrous biomass slow to break down; runs to seed quickly if stressed; N-hungry at decomposition
Phacelia 6–10 Small roots improve clay surface structure; good for bees; high seed production risk; destroys easily with knife roller; black residues warm soil
Spring/winter oat 70–90 Cheap; better for autumn/winter covers; rust/aphid susceptible if drilled too early; generally survives frost and regrows in spring
Fodder radish 6–8 Versatile across soil types; good soil structure; drought-resistant; not slug-attractive; may produce some seed
Rye 70–100 Very aggressive; good soil restructuring; high C/N — mix with vetches/peas to avoid N deficit in following crop; good mulch base
Triticale 80–120 Similar to rye but slightly less aggressive and more pest/disease susceptible; best as overwintered cover
Spring/winter barley 17–22 Useful and cheap but sensitive to stress and disease; not advisable in cereal rotations
Ryegrass — Slow initial growth but very aggressive once established; useful under maize; difficult to manage mechanically or chemically
Oilseed rape 8–12 Very inexpensive; good soil-structuring; needs available N; encourages slugs; don’t use in rotations that already include OSR
Fodder rape 8–12 Similar to OSR but more foliage and can be grazed

“New” or Less Common Species

Species Seeding rate (kg/ha) Notes
Sunflower 20–25 Best in hot/dry conditions; good summer biomass if planted early; killed by frost; absorbs N, P, K without providing soil cover
Rough/Brazilian oat (Avena strigosa) 35–45 Very aggressive; heavy biomass; high C/N (include legume to prevent N deficiency following crop); can be quality forage
Flax/linseed 20–30 Easy in dry conditions; low surface biomass but good root development; surface residues can block tillage tools
Buckwheat 45–55 Easy summer establishment; competes well with broadleaved weeds (allelopathic); powerful N scavenger — following crops may need extra N; attracts bees; good phosphorus scavenger; not recommended before maize, sugar beet, or sunflower
Camelina 8–12 Very small seed — sow very shallow; fast 90–100 day cycle so risk of seed production; useful as double crop or companion with legumes
Asian radish 5–8 Easy to establish; absorbs large amounts of N; does not produce stem if sown late summer/autumn; long taproot can weigh several kg; killed by −7 to −8°C frost; low C/N so returns fertility well
Turnip 6–10 Cruciferous N-scavenger; doesn’t produce stem in autumn; good for grazing; not winter-killed; continues absorbing N in spring — depletes N for cash crop
Moha millet 25–30 Needs high temperatures, water, and N; excellent forage; must be sown before mid-July (day length sensitivity); combine with legumes like Alexandra clover
Sorghum 15–25 Very aggressive tropical grass; heavy biomass when planted early; drought-resistant when established; good forage source
Black mustard 2–3 Very low seeding rate (tiny seed); longer growing cycle than white mustard — lower seed production risk; possible bio-fumigant for nematodes
Nyger 8–12 Related to sunflower; hot/moist conditions; good early biomass; first frost kills it; very attractive to slugs; useful as companion in autumn OSR (attracts slugs, then dies off)

Legume Cover Crops

“In Europe few legumes are included in crop rotations, so they should be included in cover-crop mixes. They bring more diversity, promote higher biomass production, fix nitrogen, and have a low C/N ratio so do not tie up soil nitrogen.”

Species Seeding rate (kg/ha) Notes
Common vetch (spring or winter) 40–50 Good nitrogen fixer; climber — smothers other species in autumn; easily controlled with knife roller; may regrow and block tine machinery; shallow root aids biological activity
Hairy vetch 35–45 More aggressive than common vetch once established; can dominate mixes; 3–5% of seeds remain dormant — may germinate in cash crop (less risk under no-till)
Bengal vetch 40–50 Same traits as common vetch but 25–40% more biomass in 3 months
Cerdagne (mountain) vetch 30–40 Well suited to dry and harsh conditions
Alexandra/Bersim clover 8–12 Annual/biannual; rapid summer/autumn establishment on fertile, moist deeper soils; 3–4 t DM/ha possible after barley/wheat; good forage; does not need destruction before next straw crop
Persian clover 8–12 Similar to Alexandra but grows better in poorer soils and harsher conditions; more frost-resistant; harder to destroy
Crimson clover 12–15 Biannual; slow autumn establishment; performs better in difficult climates than Bersim; main production in spring; good forage; not a big nitrogen fixer; useful on wet soils before maize if killed before it uses soil moisture
Field bean 150–200 Versatile despite heavy seed rate; deep taproot for soil restructuring; fixes 80–200 kg N/ha in 3–4 months; not ideal forage but can be made into silage; spring variety “Diana” (300–400g/1000 grains) achieves equal results at half seed rate
Forage pea 60–80 Versatile; bigger biomass, hardier, more disease-resistant than grain varieties; good N fixer; quality forage
Latyrus 35–45 Best on calcareous soils; toxic grain — can’t be used as forage but good companion (especially OSR); short growing cycle, frost-killed
Lentil 25–35 Calcareous, non-acidic soils preferred; low biomass but competitive at high seed rates; GFL mix (Latyrus/fenugreek/lentil) for OSR companion; black fodder lentil has more biomass but seed supply scarce

Key Principles

  • High stubble height improves cover crop establishment — reduces hairpinning, retains moisture, buffers temperature extremes, protects from CSFB (see Stubble Management and Cutting Height)
  • Mix strategy: combine 3–5 species to spread risk, balance C/N ratio, provide multiple soil functions
  • Drilling timing: many summer species must go in before mid-July; overwintered cereals can be sown later
  • Nitrogen management: high C/N species (rye, triticale, rough oat, mustard) should be mixed with legumes to prevent N immobilisation
  • Slug risk: avoid OSR, nyger, or species known to attract slugs unless managed for slug control purposes

Sources

  • [[sources/dd-issue-02]] — “Cover Crop Species: Some Species Observed, Tested and Mixed”, Frédéric Thomas & Matthieu Archambeaud, TCS Magazine (France)

Related Pages