158 Agricultural Chemistry. 



quality and contain from 2 to 9 per cent of nitrogen, 9 to 19 

 per cent of phosphoric acid and 2 to 4 per cent of potash. "Where 

 the formation has taken place in a damp climate, then ferment- 

 ation occurred, resulting in a loss of nearly all of the organic 

 nitrogen. If much rain fell, there was also a loss of nearly all 

 of the soluble potash salts and soluble phosphates. This has pro- 

 duced a product containing 15 to 30 per cent of phosphoric acid 

 in the form of insoluble phosphates of lime, iron and aluminum. 

 This material is generally converted into a soluble phosphate by 

 treatment with sulphuric acid, before reaching the market. 



Potash fertilizers. This class of materials is generally con- 

 sidered of relatively less importance as fertilizers than either 

 the nitrogenous or phosphatic fertilizers. This is true because 

 potash compounds are usually more abundant in the soil than 

 either nitrogen or phosphoric acid, and while most crops remove 

 larger quantities of potash than of phosphoric acid, the -former 

 is more likely to be returned to the soil. It has already been 

 stated that potash is most abundant in the stems and leaves of 

 plants, and as they are the materials generally returned to the 

 land in the form of manure, the drain from the soil of this con- 

 stituent is therefore much less than in the case of the nitrogen 

 and phosphoric acid. Of course, when the whole of the crop is 

 removed from the soil the loss of this constituent may be very 

 great. "While these are important facts, it must not be assumed 

 that the addition of potash fertilizers is unnecessary. It is a 

 very necessary constituent of fertilizers, being absolutely essen- 

 tial for those intended for light, sandy soils, and for peaty- 

 meadow lands, as well as for certain potash-consuming crops, as 

 potatoes, tobacco and roots. They are also of especial value for 

 clover, grass, corn and fruits; they should be applied in the 

 fall on heavy clay soils and in the early spring on sandy soil. 

 The former soils generally do not need applications of potash 

 salts as much as sandy soils, being naturally rich in this fer- 

 tilizer ingredient. 



