Leguminous cover crops: an important tool for improving resource use efficiency in organic arable cropping systems.

Cover crops are one of the most effective tools for organic farmers to improve the efficiency of their agro-ecosystems, while also reducing economic costs and environmental problems. The choice and usefulness of a cover crop species strictly depend on its adaptability to specific climate and soil conditions, but also on its relationships with other species (crops and weeds) and on the quality of farm management. Nine different pure species and three species mixtures were cultivated for two years as winter cover crops in a rainfed stockless arable organic cropping system as part of the MASCOT long-term experiment. Leguminous cover crops showed the highest level of biomass production in both years. Hairy vetch (Vicia villosa), either in pure stand or in mixture with grasses, was the most productive and stable species, and had the highest N uptake (ca. 200 kg ha-1). Besides, leguminous species significantly increased the content of N (up to 100%) and P (up to 50%) in weeds and associated grass crops, probably as a result of increased nutrient availability in soil through root exudates.