CROrS XOT IN PROrOKTIOX TO NITROGEN IN SOIL. 317 



If the crops are in proportion to tlie quantity of 

 effective nitrogen in the soil, it follows that the soil of 

 Field 2 contained, not only altogether, but even propor- 

 tionately, more than Field 1. K the corn crop in Field 

 1 = 115 kilogrammes corresponded to the fraction of 

 effective nitrogen in the whole amount of nitrogen = 

 2787 kilogrammes, then Field 2 ought to have yielded 

 257 kilogrammes of corn, supposing that the relative 

 proportion of active and inactive nitrogen were the same 

 as in Field 1 (for 2787 kilogrammes, nitrogen : 115 kilo- 

 grammes, corn = 4752 kilogrammes, nitrogen : 257 kilo- 

 grammes, corn). But, in fact. Field 2 pelded two and 

 a half times as much corn ; and therefore the amount of 

 active nitrogen in Field 2 was just in the same proportion 

 greater. 



This explanation, very simple in itself, is, however, 



opposed by the fact tliat both these fields manured in the 



same year with superphosphate of lime (prepared from 



phosphorite) (see pp. 147 and 150), gave the following 



returns : — 



Ci-op, per hectare. 



Corn Straw 



kilo. c\\-t. kilo. cwt. 



1858. Field 1 maum-ed ^\-ith superphospliate of lime 654 = 12-8 13-11 = 26-5 



1857. „ 2 „ „ 1301 = 25-5 3813 = 75-0 



Hence, by the application of three nutritive sub- 

 stances, sulphuric acid, phosphoric acid, and lime, without 

 any increase of the quantity of nitrogen in the soil, 

 as much corn was obtained from Field 1, containing 

 2787 kilogrammes, nitrogen, as from Field 2, con- 

 taming 4752 kilogrammes. There was then in the 

 former as much eflective nitrogen as in the latter, but it 

 was deficient in certain other substances indispensably 

 necessary to produce an action. Its power to become 

 active was first exliibited when these substances were- 

 added to the field. In like maimer, the favoural^le 



