300 AMMONIA AND NITRIC ACID. 



257 kilogrammes, corn). But, in fact, Field 2 yielded 

 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 that both these fields manured in 

 the same year with superphosphate of lime (prepared 

 from phosphorite) (see pp. 148 and 151), gave the fol- 

 lowing returns : 



Crop, per hectare. 



Corn. Straw, 



kilo. cwt. kilo, cwt 



1858. Field 1 manured with superphosphate of lime 654 = 12-8 1341 = 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, with- 

 out any increase of the quantity of nitrogen in the soil, 

 as much corn was obtained from Field 1, containing 

 278T kilogrammes, nitrogen, as from Field 2, containing 

 4752 kilogrammes. There was then in the former as 

 much effective 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 exhibited when these substances were 

 added to the field. In like manner, the favourable in- 

 fluence of superphosphate upon Field 2 was exhibited ; 

 for the crop of this plot, when unmanured, did not cor- 

 respond to the amount of active nitrogen which it con- 

 tained ; but by the addition of superphosphate the crop 

 rose to more than double. And when to the super- 

 phosphate upon Field 1, 137 kilogrammes of common 

 salt, and 755 kilogrammes sulphate of soda were added, 

 there was a still greater increase, i. e. there were now 

 700 kilogrammes of corn, and 1550 kilogrammes of 

 straw, a still greater quantity of apparently inactive 

 nitrogen having been rendered effective. 



The intelligent farmer who reflects upon questions 

 of this kind, will be led to the conclusion, that an essen- 

 tial difference may exist between his own practical 

 experience and the theories of the school which seeks to 



