234 



NITRIFICATION 



Nitrification had also set in, since the earliest running con- 

 tained nearly twice as much nit'ric nitrogen as was found in 

 the sample taken a fortnight earlier, before the application 

 of the manure. The proportion of nitrate continued to 

 increase, and reached its maximum in the discharge three 

 weeks later, by which time the nitrification of the ammonium- 

 salts must have been far advanced towards its completion. 



TABLE LXXXIV. Nitrogen and Chlorine in Drainage Water from 

 Plot 15. Parts per million. 



The last column of the Table shows the relation between 

 the nitric nitrogen and the chlorine in the drainage water. 

 The chlorine is derived from the ammonium-salts of the 

 manure, and as it is in no way retained by the soil its 

 appearance in the drainage indicates the movements of 

 soluble salts in the soil independently of the production of 

 nitrates. In the earlier runnings the chlorine was present in 

 great excess, being immediately derived from the manure ; in 

 the later months the proportion fell as it became washed out, 

 and by December it had again reached the normal level it 

 had showed before the manure was put on. Meantime the 

 proportion of nitrate was being maintained by constant nitri- 

 fication in the soil, so that the ratio of nitric nitrogen to 

 chlorine in the drainage water rose rapidly towards the end 

 of the winter. 



When ammonium-salts are applied as a top-dressing in the 



