Claims checked › Claim
Cover crops are always good for the soil
“Planting a cover crop is always good for your soil and your next crop.”
A real finding quoted without its condition. Above roughly 700 mm of annual rain the following crop gains. Below it, the cover crop drinks water the cash crop needed, and the same trials show yield losses of 11 to 12%.
Where it comes from
Cover cropping has strong evidence in humid climates, and that evidence has been generalised into universal advice. The generalisation is the error.
Who benefits
Seed merchants and advisory services, and, less obviously, anyone whose message is that regenerative farming has no trade-offs.
What the evidence says
Meta-analysis of dryland systems finds cover crops reduce the following cash crop by 12% in dry climates and 11% in temperate drylands, against a gain of 4% in continental Europe, with roughly 700 mm of annual precipitation as the break-even below which they stop paying in yield terms. Legacy effects in drylands averaged −7% yield, −18% soil water and −25% soil mineral nitrogen (Agronomy for Sustainable Development, 2022). Timing is the lever: in the same trials, early termination gave +12% cash-crop yield while late termination gave −61%, because the late cover depleted soil water by 7% at planting. Late termination also stored the most carbon, so the carbon and water goals pull against each other. Much of Mediterranean and south-eastern Europe sits below the 700 mm line.
What to say instead
"Above about 700 mm, yes, and terminate early. Below it, a cover crop can cost you the next harvest; keep residue on the surface instead." And check the money: UK costings found cover crops reduced gross margin in 95% of situations even where the agronomy was favourable. The cover crops page and the decision tool apply the rainfall condition for you.