FOOD FOR PLANTS 183 



Russell (4) refers further to losses of nitrogen as 

 follows : 



One of the Broadbalk wheat plots receives annually 14 

 tons of farmyard manure per acre containing 200 pounds of 

 Nitrogen. Only a little drainage can be detected and there 

 is no reason to suppose that any considerable leaching out 

 of Nitrates occurs, but the loss of Nitrogen is enormous 

 amounting to nearly 70 per cent, of the added quantity. 



The condition for this decomposition appears to be copi- 

 ous aeration, such as is produced by cultivation and the 

 presence of large quantities of easily decomposable organic 

 matter. Now these are precisely the conditions of intensive 

 farming in old countries and of pioneer farming in new 

 lands, and the result is that the reserves of soil and manurial 

 Nitrogen are everywhere being depleted at an appalling 

 rate. 



Russell refers to the recuperative actions that are 

 going on, but says: "One of the most pressing prob- 

 lems at the present time is to learn how to suppress 

 this gaseous decomposition and to direct the proc- 

 esses wholly into the Nitrate channels. 



In a paper on the Nitrate content of cultivated and 

 uncultivated soils, Blair and McLean (1), have called 

 attention to the loss of nitrogen from cultivated soils 

 and also to the low recovery from nitrogen applied as 

 organic materials. They point out that land under 

 cultivation is gradually being depleted of its store of 

 nitrogen even when nitrogenous fertilizers are ap- 

 plied each year and that the average recovery of 

 nitrogen applied in the form of fish scrap for a period 

 of nine years, was only 36.36 per cent. 



With the same nitrogen treatment soils allowed to 

 run wild just about maintained their nitrogen con- 



