CHAPTER VII 



PHOSPHATE FERTILIZERS 



210. Importance of Phosphorus as Plant Food. 



Phosphorus in the form of phosphates is one of the 

 essential elements of plant food. None of the higher 

 orders of plants can complete their 

 growth unless supplied with this 

 element in some form. The illus- 

 tration (Fig. 31) shows an oat plant 

 which received no phosphates, but 

 was supplied with all of the other 

 elements of plant food. As soon as 

 the phosphates stored up in the 

 seed had been utilized, the plant 

 ceased to grow, and after a few 

 weeks, died of phosphate starvation, 

 having made the total growth 

 shown in the illustration. All crops 

 demand their phosphates at an early 

 stage in their development. Wheat 

 Fig. 31. takes up eighty per cent, of its 



Oat plant grown phosphoric acid in the first half of 



without phosphorus . . - , ., , 



the growing period, 37 while clover 

 has assimilated all of its phosphoric acid by the 

 time the plant reaches full bloom. 43 Phosphates ac- 

 cumulate, to a great extent, in the seeds of grains and 

 hence are sold from the farm when grain farming is 

 extensively followed. All crops are very sensitive to 



