Green manures are crops grown within a rotation to improve soil structure and fertility by increasing the soil organic matter.
They can also protect the surface of the soil and prevent crusting as a “cover crop” and capture soil nutrients, particularly nitrate, reducing losses as a “catch crop” as well as providing other agronomic functions such as weed suppression and supporting beneficial insects.
There are two main types of green manures, long-term green manures grown for at least 1 year before incorporation, and short-term green manures designed to be grown for 2-4 months (summer green manures) or 6-8 months (winter green manures) between two successive cash crops.
The cultivation of short-term green manures is a promising approach for supporting soil and nutrient management. Trials of short-term green manures, as part of the Maximising Organic Production Systems EIP, showed consistent beneficial effects over the three years in organic horticulture production.
This included better weed control, more beneficial insects, more and greater functional diversity of soil bacteria, greater soil organic matter content, and earlier-developing cash crops. Importantly, cost-benefit analysis also showed that extra financial returns be achieved from growing short-term green manures as well as the potential to extend rotations.
