24 



Lastly, in July-August 1885, samples were taken 



rom the wheat-fallow, the Trifoliurn repens, the 



Melilotus leucantha, and the Medicago sativa, plots ; 



again in each case to the depth of 12 times 9 inches, or 



108 inches. 



It was in the case of these Leguminous plant plots, 

 and, for comparison, in that of the alternate wheat and 

 fallow plots, that samples were first taken to so great a 

 depth as 12 times 9 inches; and here the natural 

 unevenness of the subsoils, as observed in other fields 

 to a less depth, was extremely marked. Nevertheless, 

 the determinations of nitrogen as nitric acid at the 

 different depths, on the plots where the different plants 

 had grown, gave results of very great interest. The 

 general result was, that less nitrogen as nitric acid 

 remained in the land to a given depth, the greater the 

 quantity of nitrogen removed in the crops. In illustra- 

 tion it may be stated that, after the Vicia sativa had, 

 over a series of years, yielded much more nitrogen in 

 crops than Trifoliuin repeus, the Trifoliurn repens soil 

 was estimated to contain per acre to the depth of 12 

 times 9 inches, or 9 feet, about 146 Ibs. of nitrogen as 

 nitric acid ; whilst the Vicia sativa soil indicated, in 

 one case only 64, and in another about 55 Ibs. ; and 

 again, after Medicago sativa had, for some years, yielded 

 very much more nitrogen than Trifolium repens, the 

 soil of the latter contained more than 100 Ibs. of 

 nitrogen as nitric acid, but that of the Medicago sativa 

 less than 20 Ibs. 



A study of the results led to the conclusion, that 

 each of the Leguminous crops had taken up nitrogen as 

 nitric acid from the soil and subsoil, and that the plants 

 which had the greatest root-range had so taken up the 

 most. But, at any rate in the case of the Medicago 

 sativa, the figures did not justify the conclusion that 

 the whole of its nitrogen had been so derived. Assum- 

 ing that it were not, it is obvious that the deep-rooted 

 plant had either taken up combined nitrogen from the 

 subsoil in some other form, or that free nitrogen had, 

 in some way, been brought under contribution ; or 



