Studies of soil after fifty years of wheat or barley cropping, especially of soil made acid with sulphate of ammonia

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Abstract
1. Monthly aqueous extracts of soils which have been under wheat and barley cropping on the Woburn light sandy loam soils, with various manuring show very great similarity in the amount and character of the materials extracted in the wheat and the barley soils.2. Water-soluble phosphoric acid and potash are in extremely small amount where these manures have not been applied during the fifty years’ treatment, but, in spite of this, the amount of these constituents does not appear to be a limiting factor in determining the yield of either wheat or barley. The phosphoric acid is much higher in the plots treated with phosphatic manures, and the potash is slightly higher in those treated with potash manures, but these facts do not seem to have secured a seriously higher yield.