264 DEY-FARMING 



While it is undoubtedly true that dry-farm crops 

 are naturally drier than those of humid countries, 

 yet it must also be kept in mind that the driest dry- 

 farm crops are always obtained where the summers 

 are hot and rainless. In sections where the precipi- 

 tation comes chiefly in the spring and summer the 

 difference would not be so great. Therefore, the 

 crops raised on the Great Plains would not be so dry 

 as those raised in California or in the Great Basin. 

 Yet, wherever the annual rainfall is so small as to 

 establish dry-farm conditions, whether it comes in 

 the winter or summer, the cured crops are drier than 

 those produced under conditions of a much higher 

 rainfall, and dry farmers should insist that, so far as 

 possible in the future, sales be based on dry matter. 



The nutritive substances in crops 



The dry matter of all ]jlants and plant parts con- 

 sists of three very distinct classes of substances: 

 First, ash or the mineral constituents. Ash is used 

 by the body in building bones and in supplying the 

 blood with comj^ounds essential to the various life 

 processes. Second, j^rotein or the substances con- 

 taining the element nitrogen. Protein is used by 

 the body in making blood, muscle, tendons, hair, and 

 nails, and under certain conditions it is burned within 

 the body for the production of heat. Protein is 

 perhajjs the most inr]3ortant food C(jnstituent. Third, 



