CHAPTER VI 



THE BOOKKEEPING THEORY OF 

 SOIL FERTILITY 



THE vital question for the Farmer of To- 

 morrow, however, is not how much land there 

 is, but how much fertility there is in the land 

 that he possesses, or may finally possess. How 

 long, in other words, at a given rate of pro- 

 duction, will the soil continue to feed us? 



The acres are counted, are definite in num- 

 ber. There never can be any more acres, and, 

 once the last of arable land has been put under 

 the plow, the only means of producing more 

 food is to speed up the machine to take more 

 out of the soil. That brings us to the most 

 important, and, at the same time, the most per- 

 plexing, of the problems confronting the 

 farmer of the future. 



How much fertility is there in the soil? 



Malthus preached a theory of doom a cen- 

 tury ago, and kept all Europe gloomy for 



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