The Broadbalk Wheat Experiment 1968-78: Yields and Plant Nutrients in Crops Grown Continuously and in Rotation, G. V. DYKE, B. J. GEORGE, A. E. JOHNSTON, P. R. POULTON and A. D.TODD (1983) Rothamsted Experimental Station Report for 1982 Part 2 - pp 5 - 44