6 RESULTS OF EXPERIMENTS AT ROTHAMSTED, 



nitrogen after the removal of 151-3 Ibs. in Clover, than after the 

 removal of only 37-3 Ibs. in Barley. 



The fact is, that the Clover had not only yielded so much more 

 nitrogen in the removed crops, but it had also left the surface soil 

 considerably richer in nitrogen. Thus, in October, 1873, after the 

 removal of the Barley and the Clover, samples of soil were taken from 

 10 places on each of the two portions, and the nitrogen was determined 

 in the samples from each of 4 of the individual holes separately, in the 

 mixture of the 4, and in the mixture of the samples from the other 6 

 places. The determinations in the numerous separate samples consist- 

 ently showed that, to the depth of 9 inches, the Clover-land soil which 

 had yielded so much more nitrogen 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 the dry fine soil, 

 of the Clover, 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 debris had 

 first been removed from the samples. It was further found, that the 

 above- and under-ground vegetable residue picked from the Clover-land 

 samples, was much more in quantity, and contained much more nitrogen, 

 than that from the Barley-land samples. 



In 1874, and in 1875, barley only was sown over both portions. 

 In 1876, barley was again sown over the whole of the land, with 

 Clover as well on the portions where it had been grown in 1873 ; but 

 the plant failed in the winter, and gave no crop in 1877. In 1877, 

 Barley was again sown over the whole ; this time with Clover on half 

 of the previously Clover portion, and on half of the previously only 

 Barley portion. In the autumn of 1877, soil samples were again taken ; 

 this time from 4 places on each of the differently cropped portions. 

 The determinations of nitrogen in the surface soils consistently showed, 

 as before, a higher percentage where Clover had grown than where only 

 Barley had grown. 



It is, of course, well known in agriculture, that the growth of 

 Clover, which removes much more nitrogen than a cereal crop, increases 

 the produce of a succeeding cereal as if nitrogenous manure had been 

 applied. But what I wish specially to direct attention to is, the fact 

 that a Leguminous crop accumulates a great deal more nitrogen over a 

 given area than a Gramineous one under equal soil conditions. 



YIELD OF NITROGEN IN THE CROPS OF A MANURED ROTATION. 



Before considering the effects of direct nitrogenous manures on the 

 different crops, it will be well to form some idea of the amount of 

 nitrogen yielded in fairly good crops grown in rotation, with fairly 

 liberal manuring. This point may conveniently be illustrated by the 



