The Nitrogen of Farmyard Manure- 193 



are based on the best available data. Of nitrogen it is 

 estimated that the farmyard manure will, on the average, 

 contain O64 per cent., and, therefore, that 20071b. were 

 applied per acre per annum ; or, in all, 16061b. in the eight 

 years. During the eight years the produce removed about 

 29 per cent, as much nitrogen as is thus estimated to be 

 supplied in the manure ; during the next six years about 

 20 per cent. ; and during the last six of the twenty years 

 about 10 per cent, more was removed, making a total of 

 about 59 per cent, as much removed in the whole produce of 

 the twenty years as had been supplied during the eight 

 years. But it must not be assumed that the whole of the 

 nitrogen of the crops came from the manure. It would be 

 more correct to deduct the amount obtained in the un- 

 manured produce, and to regard only the so-reckoned increase 

 as due to the manure. Estimated thus, only 10*4 per cent, 

 of the supplied nitrogen was recovered as increased yield 

 during the eight years of the application ; only 6 per cent, 

 more during the next six years; and only 1*7 per cent, 

 during the second six years since the application ; making, 

 in all, a recovery as increase during the twenty years of 

 about 18'1 per cent, of that supplied in the first eight years. 



Thus, on the supposition that the whole of the nitrogen of 

 the produce was derived from the manure, there would still 

 remain, at the end of the twenty years, about 41 per cent. 

 of the 16061b., or about 6581b., not accounted for. But, on 

 the supposition that only the increase above that in the un- 

 manured produce was derived from the manure, which is, 

 doubtless, at any rate much nearer the truth, there would 

 remain unaccounted for, at the end of the twenty years, 81*9 

 per cent, of the nitrogen supplied that is, about 13151b. ; 

 and yet, during the last six years of the twenty, less than 

 2 per cent, of the original amount supplied was recovered as 

 increase. The prospect of recovering the whole, or even a 

 considerable proportion would thus seem, to say the least, 

 extremely remote. 



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