AVAILABLE PHOSPHATE 199 



also. After the extraction, the bones crumble readily and are 

 easily ground. Bone meal is a much-used fertilizer, especially by 

 truck gardeners. About 100 to 300 pounds and more may be 

 applied per acre. 



Acid Phosphate. Acid phosphate is made by treating an 

 insoluble phosphate with an acid and thereby changing it into a 

 soluble phosphate. This is the most easily soluble phosphate 

 fertilizer. The name " superphosphate " is sometimes applied to 

 it. The manufacturing process consists mainly in treating rock 

 phosphate with sulphuric acid. Because of its availability, or 

 solubility, acid phosphate is very generally used, especially when 

 immediate results are desired. Applications may vary from 100 

 to 500 pounds per acre. 



Many Soils Need Phosphates. Many soils are particularly 

 deficient in phosphorus, either because they never contained any 

 appreciable supply, or because of exhaustive cropping. Phos- 

 phorus deficiency is especially prevalent in sections where, during 

 the early days, wheat was the one crop raised. So far as the soil 

 is concerned, that was a period of most wasteful farming. 5 Noth- 

 ing was returned to the land, the grain and other products were 

 sold, and the straw was burned. The organic matter was rapidly 

 used up and the phosphorus was carried away with the wheat. The 

 only way to correct this phosphorus deficiency and to maintain a 

 sufficient supply in the soil is to buy phosphorus and add it to the 

 land. Phosphorus may be purchased in the form of fertilizers and, 

 to a lesser extent, in the form of feeds, such as bran, for example. 

 The feeds when fed enrich the manure produced. 



It is common experience to obtain crop increases of from ten 

 to fifty per cent and more by using phosphate fertilizers. The 

 important effects produced by supplying sufficient phosphorus are : 

 (a) The grain fills better and consequently weighs more per unit 

 volume; (6) plants develop strong and extensive roots, and (c) 

 crops often mature earlier. 



In general, the following soils are benefited by phosphate 

 fertilizers : Soils exhaustively cropped, peat and muck soils, sands, 

 and black, acid loams, and silt loams. 



Available Phosphate More Important Than Total. The 

 amount of phosphorus that crops can secure is of more importance 



5 The pioneer wheat-farmer can hardly be blamed for his system of farm- 

 ing. The fact that the soils were rich enough to grow good crops of wheat 

 made possible the construction of roads, the building of cities, and general 

 developments which are enjoyed today. 



