XXII 



THE FERTILITY OF THE SOIL 



rilHEEE is no problem of greater importance to the 

 A prospective farmer than the fertility of the soil. 

 The idea conveyed by the above expression is extremely 

 indefinite to most persons. It is generally known that 

 the crops vary from year to year and from field to field. 

 The causes of this variation are well known in many 

 respects. They are largely seasonal. The amount 

 and distribution of the rainfall, the amount and dis- 

 tribution of heat, and the amount and distribution of 

 light, are very potent factors in vegetable growth. If 

 the farmer could have available three inches of water 

 per month for the growing months of May, June, July 

 and August, he would need only a foot of rainfall to 

 produce a magnificent crop. Unfortunately for the 

 farmer, he does not control the natural distribution of 

 water. In this respect the irrigation farmer has a 

 great advantage, and thus the magnitude of the crop 

 under irrigation can be foretold with a great deal of cer- 

 tainty. 



WHAT IS FERTILITY? 



Aside from the seasonal variations of water, heat 

 and light, there are other causes which control the mag- 

 nitude of the crop. These causes are grouped together 

 under the term " fertility." To describe fertility in a 

 single phrase is rather difficult, but not impossible. 



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