39 



in 

 ho 

 he 



est 

 ihe 



bat mineral manure alone during the thirty years, yielded an average 

 of 20*3 pounds of nitrogen in the crops, and 12 pounds in the drain- 

 age, or in all 32 "3 pounds per acre per annum. It would thus 

 appear that, without nitrogenous manure, about 30 pounds of nitrogen 

 has been contributed per acre per annum, from some source, to crop 

 and drainage together. The determinations of nitrogen in the soils of 

 the two plots indicate that they have lost an average of about two- 

 thirds of this amount annually to the depth of 27 inches. There 

 would, therefore, according to this reckoning, i-emain about one-third 

 — say 10 pounds more or less — to be contributed by seed, by rain and 

 condensation from the atmosphere, and by all the other supplies of 

 combined nitrogen which have been supposed to be available, whether 

 by the combination of free nitrogen within the soil, or its assimilation 

 by the plant. Of this amount about 2 pounds will be due to seed, 

 and if we suppose, say, only 5 pounds to be annually supplied by rain 

 and the minor aqueous deposits from the atmosphere, there is but 

 little left to be provided by all the other sources assumed. 



Nitrogen in the Soils of the Experimental Barley Plots. 



Unfortunately we have not so complete a series of determinations 

 of nitrogen in the soils of the experimental barley plots as of those in 

 the experimental wheat field. In 1868 four of the barley plots were 

 sampled. Four samples, each 6 by 6 inches area, by 9 inches deep, 

 were taken from each plot, and the four mixed together. In March, 

 1882, 26 plots were sampled, four samples being taken from each plot, 

 each 6 by 6 inches area, and to the depth of three times 9, or 27 

 inches. Of the plots sampled in 1868 only one had received no nitro- 

 genous manure, but we are able to give the percentage of nitrogen in 

 the surface soil of this plot at the two dates. 



Table XI. — Hoosfield Barley Land. 



Nitrogen^ per cent, in the dry Mo^dd, first 9 inches. 



[Barley, 31 years in succession, 1852-1882 inclusive.] 



The calculated average weights of dry mould per acre, to the depth 

 of 9 inches, were not very different at the two dates. The 1882 samples 



■ l iv _ 



