104 



THE ROTHAMSTED EXPERIMENTS. 



The table shows that the barley yielded 37.3 lb. of nitrogen 

 per acre, whilst the three cuttings of clover contained 151.3 

 lb. In the next year, 1874, barley was grown over both 

 portions ; and on the one where barley had yielded 37.3 lb. 

 of nitrogen in the previous year, it now yielded 39.1 lb. ; but 

 on the portion where the clover had yielded 151.3 lb., the 

 barley succeeding it yielded 69.4 lb. That is to say, the 

 barley yielded 30.3 lb. more nitrogen after the removal of 

 151.3 lb. in clover, than after the removal of only 37.3 lb. in 

 barley. 



TABLE 33. — Nitrogen per acre in Barley and in Clover, 

 grown in Little Hoosfield, Rothamsted. 



Clover en- The fact is, that the clover had not only yielded so much 

 ricking soil m0 re nitrogen in the removed crops, but it had also left the 

 xnmrogen. sur f ace _ so ii considerably richer in nitrogen. Thus in October 

 1873, after the removal of the barley and the clover, samples 

 of soil were taken from ten places on each of the two portions, 

 and the nitrogen was determined in the samples — from each 

 of four of the individual holes separately, in the mixture of 

 the four, and in the mixture of the samples from the other 

 six places. The determinations in the numerous separate 

 samples consistently showed that, to the depth of 9 inches, 

 the clover-land-soil, which had yielded so much more nitro- 

 gen in the crops, was nevertheless determinably richer in 

 nitrogen than the barley-land-soil, which had yielded so much 

 less. This is sufficiently illustrated by the following figures, 

 showing the mean percentage of nitrogen in October 1873, in 

 the fine dry soil, of the clover-land, and of the barley-land, 

 respectively : — 



Mean per cent 

 nitrogen. 

 In clover-land-soil .... 0.1566 



In barley- land-soil .... 0. 1416 



This was the case notwithstanding that all visible vegetable 

 ddbris had first been removed from the samples. It was 



