36 



RESULTS OF EXPERIMENTS AT ROTHAMSTED, 



TABLE XVII. 



Nitrogen as Nitric Acid, per acre, Ibs., in the soils and sub-soils of some experimental 

 plots, without Nitrogenous Manure for more than 30 years. 



Hoosfield, Rothamsted. 

 Samples collected July 29 to August 14, 1885. 



The Table of the estimated nitrogen in the produce per acre 

 (p. 32), shows that, whilst from the commencement to 1885 inclusive, 

 the Trifolium repens yielded only 261 Ibs. of nitrogen in crops, the 

 Medicago gave 917 Ibs. ; and again, whilst in 1885, the year of soil- 

 sampling, the Trifolium gave only 97 Ibs., the Medicago gave 270 Ibs. 

 It is further to be observed that, quite accordantly with the usual 

 character of growth of Lucerne in agriculture, with the increasing 

 root-range, and consequently increased command of the stores of the 

 soil and sub-soil, the yield of nitrogen increased from 28 Ibs. in the 

 first and second years, to 337 Ibs. in the fifth year of growth, declining, 

 however, somewhat afterwards. 



Under these circumstances of very large yields of nitrogen in the 

 crops, there is, at every one of the twelve depths, less, and at most 

 very much less, nitrogen as nitric acid remaining in the soil than where 

 so much less had been removed in the Trifolium repens crops. The 

 difference is distinct even in the upper layers ; but it is very striking 

 in the lower depths. Thus, there is, on the average, not one-twelfth 

 as much nitric-nitrogen in the lower 10 depths of the soil of the 

 deep-rooting and high-nitrogen yielding Medicago saliva, as in those of 



