Cover Crops for Soil Health: What to Plant & Why

Updated 2026-07-10 · Soil & fertility

A cover crop is grown to feed and protect the soil rather than to sell. Done well it is the cheapest way to build organic matter, fix free nitrogen, break pest cycles, smother weeds and stop erosion — turning your off-season from a liability into an investment in next year’s yield.

What cover crops do for you

• Build organic matter & feed soil life — living roots keep microbes and mycorrhizae fed year-round.
• Fix nitrogen — legumes can add meaningful N for the following crop.
• Stop erosion & hold nutrients — cover keeps soil and nitrates from washing away over winter/monsoon.
• Smother weeds and break pest/disease cycles between related cash crops.
• Relieve compaction — deep taproots (radish) open the subsoil.

Choose by the job you need done

Pick the family that matches your goal:

• Legumes (sunn hemp, cowpea, clover, vetch, dhaincha) — fix nitrogen; best before a hungry crop like maize or a vegetable.
• Grasses/cereals (rye, oats, sorghum-sudan, millet) — lots of biomass, scavenge nitrogen, smother weeds, great erosion cover.
• Brassicas (mustard, tillage radish) — bust compaction and biofumigate against some soil pests.
• Mixes — combine a legume + grass + brassica to get several benefits at once and more resilient cover.

Fit it into your rotation

Use whatever window you have: a winter cover after a summer crop, a summer green manure before a winter crop, or a fast catch crop in a short gap. Sow densely into a firm, moist seedbed for quick ground cover. In hot regions a 45–60 day sunn hemp or dhaincha green manure before the main crop is a classic, cheap fertility builder.

Terminate at the right time

The biggest mistake is letting a cover crop go to seed (it becomes next year’s weed) or robbing the cash crop of moisture. Terminate at or just before flowering, when biomass and nitrogen peak:

• Incorporate as green manure 2–3 weeks before planting, or
• Roll/crimp or mow and plant into the residue for no-till moisture conservation.

Leave a short gap before sowing the cash crop so decomposition does not tie up nitrogen at emergence.