268 POWER OF THE SOIL TO ABSORB SALTS [chap. 



the low winter temperatures will not permit of much 

 nitrification. Liquid manure and similar materials 

 containing such readily nitrifiable substances as urea 

 and ammonium carbonate, should be reserved until 

 early spring, so that the crop may be growing whenever 

 nitrification begins. Ammonium salts are very rapidly 

 nitrified, so that they should only be used in spring. 

 At Rothamsted nitrates begin to appear in the drainage 

 water immediately after the application of the ammonium 

 salts to the wheat plots in March if rain falls, and one 

 of the plots which has its ammonium salts applied in 

 autumn shows not only a considerable falling -off in 

 crop but also large quantities of nitrates in the winter 

 drainage waters. 



The following table shows the amounts of nitrates 

 removed in the drainage water from the two plots which 

 receive 400 lbs. per acre of ammonium salts with mineral 



1879-1881. Lbs. of Nitric Nitrogen per Acre. 



manures, only differing in the fact that on plot 7 the 

 ammonium salts are sown in March, and on plot 15 in 

 October ; also the average crops of grain and straw for 

 the twenty-three years, 1875-97. 



That sulphate of ammonia will to some extent 



