This technique involves sowing a beneficial, non-competing crop to grow with the main crop during the early part of the season. The companion crop will then die off naturally from adverse weather conditions or due to competition from the main crop.
Not only does this reduce the room for weed species to establish but it also locks up nitrogen meaning less reliance on additional chemical inputs. The companion plant can also help to attract pests away from the cash crop by providing a more appealing alternative.
Companion plants with a more robust root structure can also encourage the main crop to grow deeper roots allowing better access to nutrients and water. The companion crop is usually chosen for its frost susceptibility so that it dies off naturally allowing the main crop to take over once it is fully established.
Trials with OSR have shown that gross margin can be increased with better yields and lower input requirements. The trials demonstrated:
The companion plants can replace, in part, the need for chemical inputs and mechanical preparation of the soil, meaning that the risk of soil erosion and diffuse pollution is reduced. Healthier soils enable soil invertebrates to thrive, providing food for organisms further up the food chain. A lesser reliance on chemical fertilisers and pesticides reduces the impact on pollinators and aquatic habitats.