Chop And Drop

Chop and drop means growing plants for their leaf and stem, cutting them where they stand, and leaving the cut material lying on the ground as mulch - a layer of dead plant matter covering bare soil. Nothing is carried in and nothing is carried away, which is the difference between this and mulching a bed from a bought pile. It produces nothing on its own, though: it depends on a standing planting of fast-growing plants nearby grown to be cut.

Quantity decides whether it does anything. A thin scattering is not a mulch; to slow evaporation the layer should cover at least 90 percent of the soil, which takes about 4.5 tonnes of dry material per hectare (4,000 lb per acre). A well-grown stand can give 12 t/ha (11,000 lb/acre) unwatered. Most of what it returns is not new. Cut hedgerow material dropped for a grain crop carried 231 kg of nitrogen per hectare, of which only about 42 kg was a real gain to the site; the rest was nitrogen already circulating there. It is a fertility loop rather than a fertility source, and material cut near planting time feeds the coming crop far better than material cut later.

The usual way it goes wrong is that woody or straw-like cuttings take nitrogen out of the ground while they rot instead of releasing it: they hold too much carbon, so the microbes breaking them down borrow the nitrogen they lack from the soil beneath, and a hungry crop planted straight behind goes backwards first. Fresh cuttings from some species also release chemicals that stunt seedlings, sown crop and weed alike. The layer keeps soil cooler, so a sowing behind it is timed by soil temperature rather than the calendar, and it can shelter the insects and diseases it is meant to suppress. Leave stalks whole rather than shredded, since whole stalks hold weeds down much longer. It needs nothing but loppers, pruners or a blade; the cutting itself is the cost.