Soil Health and Fertility

Abstract

SOIL HEALTH AND FERTILITY 5. New Zealand cover crop literature review Key points • Cover crops are short term crops, sown after a main crop has been harvested or undersown into a main crop, grown over the winter and then grazed or incorporated into the soil before the next crop is sown. • Cover crops can provide nutrients to the following crop, provide grazing, prevent nutrient leaching, protect the soil, control weeds, and leguminous cover crops fix nitrogen. • All cover crops need to be sown as early as possible to maximise their benefits. • It is usually worth grazing rather than cultivating-in to get a return on the investment and to reduce N lockup in high C:N ratio crops. 1. Nitrogen fixing cover crops • Tick beans, lupins or forage peas are flexible and productive, but require early sowing. • Mixed legume/cereal green feeds are a good idea. • Winter legumes need to be sown early, used early, and grazed rather than ploughed in. 2. Cereals and ryegrass • Oats or triticale are the most flexible and productive. • Modern feed varieties perform best. • Early planted mixed legume/cereal green feeds work well. • Winter grasses/cereals need to be sown early (can tolerate slightly later sowings than legumes) and give best results if not grazed. • Triticale, ryecorn and ryegrass tolerate early winter grazing best. 3. Forage brassicas • Winter brassicas need to be sown early to achieve a high yield. • Brassicas can be a useful break crop in the cropping rotation.