ON THE GROWTH OF LEGUMINOUS CROPS. 



33 



amount of nitrogen existing as nitric acid, at each depth. Table XVI. 

 summarises the results. 



TABLE XVI. 



Nitrogen as Nitric Acid, per acre, Ibs., in soils of some experimental plots, 

 without Nitrogenous Manure for more than 30 years. 



Hoosfield, Rotharnsted. 

 Samples collected July 17-26, 1883. 



SUMMARY. 



The first point to notice is that, at each depth, from the first to the 

 twelfth, the Trifolium repens soil contains much more nitrogen as nitric 

 acid than the Wheat fallow soil ; and, as the figures at the bottom of 

 the Table show, whilst to the total depth of 108 inches, or 9 feet, the 

 Wheat fallow soil is estimated to contain per acre only 52 '4 Ibs. of 

 nitrogen as nitric acid, the Trifolium repens soil, that is the Leguminous 

 plant soil, contained to the same depth 145 '7 Ibs. 



Now, independently of the fact that the Leguminous plant plots 

 had received mineral manures, and the Wheat land had not, the 

 characteristic difference in the history of the two plots was, that the 

 one had, from time to time grown a Leguminous crop, and the other 

 had not, and the one which had grown Leguminous crops contained, to 

 the depth of 9 feet, nearly 3 times as much nitrogen as nitric acid as 

 the Gramineous crop soil. 



The difference is the greatest near the surface, but it is very 

 considerable down to the lowest depths. In the first three depths, 



E 



