EFFECT OF SUMMERFALLOWING AND ROTATION ON YIELD OF WHEAT, BARLEY AND FLAX
Yields of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and flax (Linum usitatissimum L.) were studied in various rotations over a 13-year period. During this time precipitation averaged about 10% below long term means. Wheat yields in the second year after fallow averaged about 75% of the yield in the first year after fallow, and were more variable. Continuous wheat failed in 2 years out of 13 because of excessive competition from weeds. Because of these failures, continuous wheat yields were extremely variable and averaged 55% of fallow yield. Barley performed in much the same way as wheat, except that the yield of barley was no more erratic on stubble land than on fallow. Wheat and barley yields were unaffected by other crops growing in 3-year rotations. Flax yields were depressed following flax, whether a year of fallow intervened or not. Alfalfa (Medicago sativa L.) depressed wheat yield in the first crop after breaking, even though a full year of summerfallow preceded the wheat. Alfalfa with bromegrass (Bromus inermis Leyss.), and bromegrass alone, did not affect wheat yields significantly.