The Soil 67 



ually being made available, but not with sufficient rapidity to 

 replace that removed from the field at harvest, and the yield of 

 1 crop produced will be limited by the element of this available 

 plant food present in least quantity. 



Continuous cropping of the soil, with the removal of every- 

 thing from the field results in the exhaustion of the plant food 

 which has been rendered available during the past ages. 



