The agronomic and economic potential of break crops for ley/arable rotations in temperate organic agriculture

Organic farming principles dictate that cereals cannot be grown continuously, and in practice they are rarely grown for more than 50%of the rotation. Choice of break crops to grow in addition to cereals and the fertility building phase are crucial to both the agronomic and economic success of the rotation on organic arable farms. There are four specific functions that a break crop may perform, namely, addition, conservation, and cycling of nutrients; pest and/or disease control; weed control and improvement in soil physical characteristics. Individual break crops may perform one or several of these functions. A good break crop must also produce satisfactory yields, be of marketable quality, and produce an economic return for the farmer. This review assesses the potential of 10 break crops (bean, lupin, soybean, hemp, oilseed rape, potato, carrot, swede, sugar beet, linola)in terms of their break function, their impact on the subsequent crop in temperate organic agricultural systems, and their economic value in UKagriculture. All species assessed had valuable break crop characteristics. Hemp, lupin, and faba bean had the greatest economic potential, but hemp and lupin currently generate poor economic returns. Linola and soybean are useful break crops, although soybean may have allelopathic effects on subsequent wheat seedlings. Swede, potato, and carrot are the most profitable crops, but are less valuable in the rotation in terms of soil fertility than hemp, bean, or lupin. Sugar beet and oilseed rape are difficult to grow organically and at present have limited organic markets.