SummaryThe effect of previous rotations maintained for 21 years on wheat and potatoes grown after 5 years of uniform cropping are described and discussed. Effects of length of ley in the rotation were detected in soil organic carbon, yield of wheat and yield of potatoes 6, 6 and 7 years respectively after the last ley was ploughed up. The effect of grazing the leys compared with mowing was detected in soil organic carbon and in yield of potatoes, and that of applying dung was detected in soil organic carbon and in yield of potatoes 12 and 13 years, respectively, after the last application.