Cover Crops

Plants grown between cash crops primarily to protect and build soil rather than for direct economic yield. Central pillar of Conservation Agriculture’s “permanent cover” principle.

Why Grow Cover Crops

  • Capture solar energy during otherwise bare periods (bare soil = zero photosynthesis = zero carbon capture)
  • Build soil carbon through root mass and organic matter
  • Suppress weeds physically and allelopathically
  • Fix nitrogen (legumes)
  • Feed soil biology (bacteria, fungi, earthworms)
  • Reduce wind and water erosion
  • Improve water infiltration
  • Provide livestock forage (integrated systems)

[Source: dd-issue-01, 2026-04-11]

Starting Out — Steve Townsend’s Framework

steve-townsend (Soil First Farming — Steve Townsend and James Warne) recommends a staged progression:

Years 1–2: Start Simple

  • Budget: ≤£20/ha/year
  • Simple species: mustard, volunteer OSR, linseed, oats, barley
  • Drill as early as possible — “as soon as the combine is in the field”
  • Do not oversow — drill for reliability
  • Mustard: 10 kg/ac; stubble turnips: 3–7 kg/ac
  • If poor establishment: 15–30 kg/ha N to perk up

Years 3–6: Higher Biomass

  • Budget: ~£30/ha
  • Add: sunflowers, beans, plus mustard
  • Confidence builds; system starts making economic sense

Year 6+: High Diversity

  • Add: vetches, clovers (N-fixing — work better in inherently fertile soils)
  • Higher seed prices justified by established system

[Source: dd-issue-01, 2026-04-11]

Species Notes

  • Mustard: cheap (£20/ha), good root mass, frost-kills (useful for easy termination)
  • Cereal rye: largest root system of any winter cereal; stores excess N; suppresses weeds; keeps soil cooler in summer; can be used as forage
  • Phacelia: not reliably frost-hardy — buy named variety not just “phacelia” species
  • Brassicas: wide leaves = “solar panels”; large canopy suppresses weeds; high carbon capture
  • Legumes (vetches, clovers, beans, cowpeas): fix N; C:N ratio 9–15 so release N quickly
  • Buckwheat, sunn hemp, pearl millet, sorghum: specialist summer mixes
  • Cereal rye as silver bullet: “closest thing to a silver bullet we have found” (Bill Buessing)

[Source: dd-issue-01, 2026-04-11]

Drilling Timing

  • As soon as possible after harvest — soil still has moisture; mustard needs moisture to establish
  • Organise drilling to happen while combine is in full swing
  • Broadcasting: possible but risky in year 1 on degraded topsoil; works well once worm activity is established

Termination

Chemical (conventional)

  • Glyphosate the day of drilling — moisture translocation stops 24 hours after spraying
  • Critical: do not let rain fall between spraying and drilling (cover becomes mulch, stops soil drying)
  • For blackgrass control: spray by end of January
  • Timing for living mulch (cereal rye → soybeans): plant cash crop into living cover and terminate same day; don’t terminate before planting into wet soil

Mechanical (organic / glyphosate-free)

  • Roller crimper: flattens and bruises stems to kill cover; creates weed-suppressing mulch for direct drilling through
  • Results: “few and mixed” as of 2018 in UK
  • Anglia Farmers / Innovative Farmers running field lab on alternatives (see Glyphosate Alternatives for Cover Crop Termination)

[Source: dd-issue-01, 2026-04-11]

Cover Crops as Forage — Bill Buessing Model

Bill Buessing, Axtell, Kansas: maintains cash crop or cover crop on every acre, all year since 2013.

Forage blend costs and yields:

Blend Cost/ac Estimated forage yield Growing days
Fall blend (18 species) $45.72 3,878 lb/ac 72
Summer blend $71.30 13,401 lb/ac 106
Selby Oats (single sp.) — 1,920 lb/ac 64
Bob winter oats — 2,803 lb/ac 64
  • Estimated saving: $50/ac/year in feed costs from perennial cover field alone
  • Cattle gain: 78 head (400–800 lb) on 30ac cover, 25.5 days → 2.78 lb/head/day gain; 180 lb beef/ac
  • Cover crop yields increased soybean yield by 3–4 bushels/ac vs no-till alone since 2007
  • Organic matter improved by 1% in 3 years (Haney soil health test, Oct 2015)

[Source: dd-issue-01, 2026-04-11]

Cover Crop Grazing Rules

  • Graze only ~35% of cover — leave remainder for soil cover and biology
  • Include species cattle won’t eat to maintain ground cover
  • Move cattle frequently (daily in warm months) — strip grazing with electric fence
  • Maintain back fence to protect new regrowth from re-grazing
  • “Grazing a cover crop means grazing the vegetation and leaving a good percentage of the cover left” — Buessing

[Source: dd-issue-01, 2026-04-11]

Key Principles (Steve Townsend)

  • Bare soil — whether cultivated or stubble — captures zero solar energy
  • Soil carbon is the main factor for production in soil; nutrients less available when carbon declines
  • “Chopped straw is one of the best sources of soil carbon — far too valuable to be carted off to power stations”
  • Start with cheap seed and succeed; confidence leads to investment

[Source: dd-issue-01, 2026-04-11]

Stubble Height and Cover Crop Establishment

Trial evidence (Loire-Atlantique, France, 2017) confirms that harvest stubble height is a major determinant of cover crop establishment success, especially with disc drills:

  • High stubble (40cm): best emergence and biomass across all species tested (mustard, peas, buckwheat)
  • Short straw, rolled: worst emergence — disc drills hairpin loose straw into seed furrow
  • Short straw + cultivation: marginally better than rolled alone but triggers fresh weed germination

Mechanisms: High stubble reduces wind speed at ground level (limiting moisture evaporation), improves rainfall utilisation, reduces nitrogen competition during decomposition, and physically protects seedlings from flea beetle attack.

For peas: high stubble plots fixed ~35 kg N/ha vs ~15 kg N/ha in cultivated plots — establishment quality affects nitrogen fixation capacity.

See Stubble Management and Cutting Height for full trial data.

[Source: dd-issue-02, 2026-04-11]

Species Guide

A comprehensive 30+ species reference for cover crop selection, seeding rates, and agronomic characteristics is at Cover Crop Species Guide (based on Frédéric Thomas & Matthieu Archambeaud, TCS Magazine France).

[Source: dd-issue-02, 2026-04-11]

Related Pages