454 NATURE AND PROPERTIES OF SOILS 



Ammonia may be produced very easily from the sodium 

 cyanide and used as such or changed to nitric acid by the 

 Oswald method. 



253. Relative availability of nitrogen fertilizers. 1 — It is 

 very difficult to rank nitrogenous fertilizers on the basis of 

 their rate of availability, since the conditions within the soil 

 so markedly influence the transformations, especially those 

 of a biological nature. Dried blood and ammonium sulfate, 

 for example, will give almost as quick results in a warm, well 

 aerated soil, as far as higher plants are concerned, as sodium 

 nitrate. In general, however, the nitrate fertilizers should be 

 rated as most readily available, followed in order by ammo- 

 nium salts, dried blood, tankage, and similar materials. Such 

 substances as wool, hair, and untreated leather waste should 

 rank last. 



FERTILIZERS USED FOR THEIR PHOSPHORUS 



Phosphorus is generally present in nature in combination 

 with calcium, iron, or aluminum. Some phosphates carry or- 

 ganic matter and when thus associated are generally consid- 

 ered to decompose more readily when added to the soil. 



254. Bone phosphate (Ca 3 (P0 4 ) 2 +).— Bones were for- 

 merly applied to the soil in the raw condition, either ground 

 or unground. Most bone as now sold is merely steamed or 

 boiled to remove the fat and nitrogenous matter, which is 

 used in other ways. Bone-meal comes on the market as a dusty 

 powder of characteristic odor. It contains about 27 per cent, 

 of phosphoric acid as tricalcium phosphate. Tankage, which 

 has already been spoken of as a nitrogenous fertilizer, con- 

 tains from 3 to 8 per cent, of phosphoric acid, largely in the 

 form of tricalcium phosphate. All bone phosphates are slow- 

 acting manures, and should be used in a finely ground form 

 and for the permanent benefit of the soil rather than as an 



J Thome, C. E., Carriers of Nitrogen in Fertilizers; Soil Sci., Vol. 

 IX, No. 6, pp. 487-494, 1920. 



