PHOSPHATE FERTILIZERS 173 



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

 and are usually sold from the farm, especially when 

 grain farming is extensively followed. All crops are 

 very sensitive to the absence of phosphates; an imper- 

 fect supply results in the production of light weight 

 grains. The nitrogen and the phosphates are to a 

 great extent stored up in the same parts of the plant, 

 particularly in the seed, which is richer in both 

 nitrogen and phosphorus than is any other part. 

 Nitrogen is the chief element of protein, while phos- 

 phorus is necessary to aid in transporting the pro- 

 tein compounds through the cell walls of plants. 

 In speaking of the phosphorus in plants and in fer- 

 tilizers, as well as in soils, the term phosphoric acid 

 or phosphoric anhydride is used. This is because 

 phosphorus is an acid-forming element and, as already 

 explained, the anhydride of the element is always con- 

 sidered instead of the element itself. 



209. Amount of Phosphoric Acid Removed in 

 Crops. — The amount of phosphoric acid removed 

 in an acre of different farm crops ranges from 18 to 30 

 pounds : 



Phosphoric acid 

 per acre. 



Lbs. 



Wheat, 20 bu 12.5 



Straw, 2,000 lbs 7.5 



Total 20.0 



