Reference:
A. E. JOHNSTON and P. C. BROOKES (1979) Yields of, and P, K, Ca, Mg Uptakes by, Crops Grown in an Experiment Testing the Effects of Adding Peat to a Sandy Loam Soil at Woburn, 1963-77 in : Rothamsted Experimental Station Report for 1978 Part 2 - pp 83 - 98