202 THE LIVING ORGANISMS OF THE SOIL [chap. 



Nitrogenous Dressing. 



Yield. 



Tons 



per acre. 



Nitrogen. 



In 



Manure. 



Recovered 

 in Crop. 



Percentage 

 recovered 

 per 100 in 



Cross- 

 dressing. 



PLOTS MANURED WITH PHOSPHATES AND ALKALINE SALTS. 



Nitrate of Soda . 

 Ammonium Salts . 

 Rape Cake . • 

 Ammonium Salts and 

 Rape Cake 



17*95 



15*12 



20.95 

 24.91 



86 

 86 

 98 



184 



67.2 



49*3 

 69.4 



103-0 



78.1 



57-3 

 70.9 



56-0 



PLOTS MANURED WITH DUNG. 



Nothing 



Nitrate of Soda . 

 Ammonium Salts . 

 Rape Cake . 

 Ammonium Salts 

 Rape Cake 



and 



17.44 

 24.74 



21-73 

 23-96 



24-05 



3i-6 4 

 61 -o 

 49.2 

 48-8 



36-2 



* Percentage of Nitrogen in dung recovered. 



It will be seen that all the nitrogenous cross dressings 

 produce an increase of crop when added to the farm- 

 yard manure. When the cross dressings are used on 

 plots receiving only non - nitrogenous manures, the 

 nitrogen recovered varies between 56 and 78 per cent, 

 of that supplied in the manure; when they are used 

 in conjunction with dung, the recovery of nitrogen in 

 the increased yield above that produced by dung alone 

 varies between 36 and 61 per cent. That the recovery is 

 smaller in the latter cases is due to the fact that with such 

 excessive amounts the yield ceases to be proportional 

 to the supply of nitrogen, being limited by other factors. 

 Denitrification is only likely to cause rapid loss 

 of nitrogen when large quantities of nitrate are 

 applied to undrained or sour land, or when they are 



