



52 



Table XVII. — Experiments on Permanent Meadow Land. 

 Nitrogen, per cent, in dry Mould, and per Acre. 



Although we have not previously quoted the figures, we have on 

 several occasions stated in general terms that determinations of nitro- 

 gen show a lower amount in the mineral-manured soil, approximately 

 corresponding to the increased yield in the crop. 



It is in reference to our statements on this point that M. Joulie has 

 called in question +he possibility of obtaining results of the kind appli- 

 cable to our argument. He takes the fact of the increased yield of 

 nitrogen under the influence of purely mineral manure as conclusive 

 proof of the atmospheric source of the increased amount of nitrogen 

 assimilated. He assumes that our calculations are based on determi- 

 nations of nitrogen in a sample of the mixed soil to the total depth of 

 54 inches. He calculates that in the mass of soil to that depth the 

 difference in the amount in the two cases would be far too small 

 to furnish a justitication for the important conclusion that the soil 

 was the source of the nitrogen. He objects that the roots of such 

 herbage would derive their nutriment chiefly in the superficial layers. 

 He further objects that if the diflerence we assume were a fact, it is 

 probably due to an accidental difference in the soil of the two plots, 

 such a difference having been admitted by us in the case of another 

 plot. Lastly, he suggests that if there really were the reduction we 

 suppose, it might be due to other causes — such as increased activity 

 of nitrification under the influence of the mineral manure and passage 

 of the nitrates downwards. 



In the first place, in the case of the irregularity in the condition 

 of one of the plots referred to, the difference was readily seen in the 

 section of the soil, and there was no such difference in the instance 

 now under consideratior. 



Then it is the determination of nitrogen in the first 9 inches of soil 



M 



