19 



greater at any one time is explained by the fact that 

 heavy rain fell frequently during the course of the ex- 

 periment, and washed much of it away. We may, how- 

 ever, safely conclude that during the season of the year 

 when crops are growing most freely, nitrification takes 

 place very rapidly ; and, in this way, a supply of nitric 

 nitrogen is kept up. 



We have stated incidentally that, though both organic 

 and ammoniacal nitrogen can be nitrified, yet the nitrogen 

 of ammonia compounds is much more quickly and easily 

 acted upon than that of organic substances. This may 

 perhaps be explained by the fact observed by Schloesing,* 

 that when the necessary nitrogen is present in the form of 

 nitrogenous organic matter, the nitrifying organism oxidizes 

 not only the nitrogen, but also the carbon and hydrogen of 

 the organic matter. Thus it may be said that the ferment 

 spends part of its energy in other ways than nitrification 

 ways that are without beneficial influence on the plant. 

 With compounds of ammonia, however, as the source 

 of nitrogen, the organism exercises almost the whole of 

 its oxidizing power on that nitrogen, only taking from 

 organic matter the carbon necessary for its own growth and 

 reproduction. 



As influencing our choice of ammonia compounds for use 

 as manure, it is worth noticing that sulphate of ammonia 

 is more readily nitrified than other ammonia compounds. 

 Schlcesing found the following to be rates at which the com- 

 pounds named were nitrified under favourable conditions : 



Chloride (muriate) of ammonia . oo Ibs. of ammonia per acre per day. 

 Carbonate of ammonia .... 67 ,, ,, 



Sulphate of ammonia .... 150 ,, ,, ,, 



These quantities are greater than could be expected in 

 ordinary farm land; but they may be taken as representing 

 the comparative speed with which nitrification takes place. 



Loss OF NITRATES. 



We have seen that when sulphate of ammonia is applied 

 to the soil, the am.nonia is in most cases retained by virtue 

 of the absorptive power of the soil, but that sooner or later 

 it is nitrified a nitrate (almost always nitrate of lime) 

 being formed; the change taking place most rapidly in hot 

 weather and in a somewhat moist soil. 



This inevitable and often rapid change is one that must 

 be carefully borne in mind in estimating the probable 

 effects of a dressing of sulphate of ammonia, or indeed of 

 any nitrogenous manure. For while most soils have more 

 or less absorptive power for ammonia, it must be repeated 

 that no soil has the power of holding any nitrate, except 

 in a purely mechanical way, as a sponge may hold water. 



* " Comptes Eendus," 109. 



B 2 



