FOOD FOR PLANTS 33 



It is frequently used in altogether unnecessary excess 

 in "complete" fertilizers. 



The natural plant food of the soil comes from 

 many sources, but chiefly from decaying vegetable 

 matter and the weathering of the mineral matter of 

 the soil. Both these processes supply potash and 

 phosphoric acid, but only the former supplies Nitrate, 

 Whether the soil has been fertilized or not, there are 

 certain signs which indicate the need of plant food 

 more or less early in the growth of the crop. If a 

 crop appears to make a slow growth, or seems sickly 

 in color, it does not greatly matter whether the soil 

 is deficient in Nitrate or simply that the Nitrogen 

 present has not been nitrated and so is not available ; 

 the remedy lies in the use of the immediately avail- 

 able form of Nitrate of Soda. 



