100 The Eothamsted Barley Experiments. 



bilities, purely mineral manures will not yield anything like a 

 fair crop of wheat or barley ; but that, on the same soil, a 

 comparatively small quantity of purely nitrogenous manure 

 has yielded, for twenty years in succession, not much less 

 barley than the average crop of the country ; and that 

 a larger amount gave, over six consecutive seasons, con- 

 siderably more than an average crop. This is knowledge, 

 acquired of the available mineral resources of such a soil, 

 which chemical analysis would not have afforded, and which 

 supplies, if not examples for exact imitation, at any rate a 

 very sound basis for deduction in regard to actual practice. 



By ammonia-salts (2001b. per acre) and superphosphate of 

 lime (3|cwt. per acre) together, an average produce of more 

 than 47 bushels of dressed grain, and more than 27Jcwt. of 

 straw, or considerably more than the average barley crop of 

 the country, was obtained over twenty years in succession ; 

 and the produce of grain increased, and that of straw in a 

 less degree diminished, giving a higher total produce during 

 the later than the earlier years. Notwithstanding the great 

 demand made upon the supplies of potash within the soil, 

 by the growth of the crop for so many years, by ammonia- 

 salts and superphosphate without potash, the addition of 

 salts of potash, soda, and magnesia gave no further increase 

 of grain, and very little of straw and total produce. The 

 potash-yielding capabilities of such a soil, and the beneficial 

 effects of the use of superphosphate with nitrogenous 

 manures for spring-sown corn crops, are here strikingly 

 illustrated. 



When the same mixed mineral manure (3001b. the first six 

 years, and afterwards 2001b., sulphate of potash ; 2001b. the 

 first six years, and afterwards lOOlb., sulphate of soda; 

 lOOlb. sulphate of magnesia) and 2001b. of ammonia-salts 

 were applied per acre per annum for twenty years, in the 

 autumn for wheat and in the spring for barley, the barley 

 gave more than one-half more grain, nearly one-sixth more 

 straw, and nearly one-third more total produce than the 



