EXPERIMENTS COMPARING BREAK CROPS AS A PREPARATION FOR WINTER-WHEAT FOLLOWED BY SPRING BARLEY

Oats, clover, beans (Vicia) and maize were tested as ‘ break crops’ in three experiments on land cropped frequently with wheat or barley. Barley was used as a ‘no-break’ control treatment. Test crops were winter wheat followed by spring barley; they received N-fertilizer at four rates. After barley wheat had much take-all (Gaeuman-nomyces graminis var. tritici); all the break crops decreased the take-all effectively and equally. Other soil-borne diseases were unimportant. N-fertilizer required for best yields was less, by 100 kg N/ha after clover and by 50 kg after beans, or maize, than after barley or oats. Best yields after oats, beans, clover were respectively I/O, 1-2, 1-4 t/ha better than after barley. Differences in take-all explain much of these effects. Ploughed-in trefoil did not affect take-all but gave small increases in yield. Percentage N in wheat grain was increased by fertilizer-N; it was greater after barley, maize or clover than after oats. Effects on the following barley, except those of N-fertilizer, were small. © 1979, Cambridge University Press. All rights reserved.