XI.] FERTILISERS IN ORDINARY FARMING 305 



however, repair the losses, and as regards potash the 

 losses are so small that on a loamy or clay soil they 

 would be made up b\- the continual slow weathering into 

 an available form of the insoluble potash compounds in 

 the soil. 



It is, however, a low level of production that is 

 attained in this example of an almost self-supporting 

 piece of land, and if the average yield is to be raised, 

 say to 5 qrs. of wheat and 6 qrs. of barley per acre, an 

 external supply of nitrogen must be obtained, either in 

 the form of fertilisers or feeding stuffs. Moreover, this 

 additional nitrogen must be considerably more than 

 would be contained in the extra quarter of wheat and 

 other larger crops that are grown ; there must be enough 

 to compensate for the greatly increased waste by drain- 

 age, denitrification, etc., which will accompany the higher 

 fertility of the soil. Several examples have already been 

 given to show that the greater the amount of fertiliser 

 added to the soil the smaller is the proportion returned 

 in the crop ; these are only particular cases of the 

 general rule that the wastage of nitrogen is greater 

 the higher the fertility of the soil. Fertilisers go 

 less to feed the crop directly than to maintain the 

 level of fertility of the land, and as this rises all the 

 actions which result in loss of nitrogen are increased 

 at a rapid rate. Thus the intensive farmer often 

 becomes wasteful because, after his land is in good 

 heart, he continues to add fertilisers at the same rate as 

 he did when he was building up its condition. 



It therefore follows that an account of what is 

 removed from the soil year by year by the crops or 

 animals raised upon the farm provides very little 

 guidance towards determining the amount of fertiliser 

 which must be brought in ; at a low level of production, 

 good land will practically recuperate itself without any 



U 



