22 CHARACTERISTICS OF AMMONIA SALTS 



nitrate as a spring dressing, when heavy rain follows very 

 soon after the the application of the manure, is here plainly 

 seen ; the nitrate is wasted by the rain, while the ammonia is 

 not. Of course as soon as the nitrification of the ammonia 

 salts is completed, one manure is as easily washed out of the 

 soil as the other. 



What time is required for the complete nitrification of a 

 dressing of ammonia salts in the soil ? The conditions favour- 

 able to nitrification are well known. Granted the presence 

 in sufficient quantity of the nitrifying organisms, and of the 

 food phosphates, p'otash, etc. necessary for their growth, 

 the activity of the nitrifying process depends on the proportion 

 of water, air, and carbonate of lime present in the soil, and on 

 its temperature. Nitrification is far more rapid at a summer 

 than at a winter temperature. It cannot take place in a dry 

 soil, but increases in vigour as the proportion of water rises. 

 Schloesing determined the amount of nitric acid formed in four 

 portions of the same soil maintained for thirteen months at 

 certain fixed degrees of moisture. His results were as follows : 

 Percentage of Water in the Soil. Nitric Acid formed per Million of Soil. 



9-3 i57 



14-6 172 



16-0 397 



2O'O 478 



The rate of nitrification rises with the proportion of water 

 only so long as the interstices of the soil still contain air ; if 

 the soil lacks drainage, and remains permanently saturated 

 with water after heavy rain, nitrification will cease from the 

 absence of oxygen, and denitrification will probably com- 

 mence. 



Nitrification will be greatly retarded when the soil contains 

 only a small supply of bases (usually carbonate of lime) with 

 which the nitrous acid first formed may combine, and will be 

 more speedy when the supply of such bases is abundant. 



In soils of ordinary character it is the conditions as to 

 moisture and tillage which have the greatest influence on 

 the activity of nitrification, and of these two conditions that 

 of moisture holds the first place. 



