Effect of Minerals following Ammonia-salts. 181 



herbage accumulated throughout the period an otherwise 

 unaccountably large amount of nitrogen. 



There was, over the seven years, more of every mineral 

 constituent (except soda) taken up on plot 6 with the mineral 

 manure than on plot 5 with the ammonia-salts. Of potash 

 there was nearly four times, of phosphoric acid about two and 

 a half times, of sulphuric acid about one and a half times, and 

 of silica (of which there was none in the manure) more than 

 one and a half times, as much taken up as where the 

 ammonia-salts were still used. There was, however, less of 

 every mineral constituent (except soda) taken up than where 

 the mixed mineral manure had been applied from the com- 

 mencement (plot 7). 



It is obvious that it was of potash chiefly, of phosphoric 

 acid also notably, but of most of the mineral constituents 

 more or less, that the available supply had become so 

 deficient under the continuous application of the ammonia- 

 salts. It has already been shown how ineffective was a 

 supply of phosphoric acid (superphosphate) when used alone 

 (plot 4 I.), and how comparatively little was its effect when 

 used in conjunction with ammonia-salts, but without potash 

 (plot 4&) ; and here again is strikingly brought out the 

 influence of a liberal available supply of potash within the 

 soil, both upon the quantity and the quality of the produce. 

 Lastly, such evidence as is forthcoming does not favour the 

 supposition that any considerable proportion of the nitrogen 

 of the ammonia-salts applied during the thirteen years, and 

 not recovered in the crops during the period of the applica- 

 tion, remained in an available condition in the soil, and was 

 reclaimed in the succeeding seven years under the influence 

 of the mixed mineral manure. 



15. Equal Nitrogen and equal Potash, in Nitrate of Soda 

 and Sulphate of Potash, and in Nitrate of Potash; in 

 each case with Superphosphate of Lime : Plots 19 and 20. 

 The marked effects of nitrate of soda and of sulphate of 

 potash pointed to the desirability of determining whether 



