58 SUCCESSFUL FARMING 



with steam contains only about 1 per cent of nitrogen and 22 to 23 per 

 cent of phosphoric acid. The steamed bone is more finely ground than 

 the raw bone, and since the fat and gelatin are removed it decomposes 

 more rapidly and is, therefore, more readily available as plant food. 

 While the phosphorus in both forms of bone is largely insoluble, it is never- 

 theless more readily available than that in rock phosphate. 



Potassium. Muriate of potash (KC1), the chief source of potash, 

 contains the equivalent of about 50 per cent of potash (K 2 0). It is the 

 most common purified potash salt, consisting chiefly of potassium chloride. 

 It is a very satisfactory source of potash for all crops excepting tobacco 

 and potatoes. This form, on account of its contents of chlorine, causes 

 a poor burn in tobacco used for smoking purposes. The chlorine is sup- 

 posed to be slightly detrimental to starch formation, and for this reason 

 the sulphate and carbonate of potash are considered superior for potatoes. 



Potassium sulphate also contains the equivalent of 50 per cent of 

 potash (K 2 O). Kainite a low-grade material- contains about 12 per 

 cent of potash. 



Wood ashes are aiso a source of potash. They contain about 6 per 

 cent of this constituent, together with about 2 per cent of phosphoric 

 acid and a large amount of lime. The availability of the potash in ashes 

 is rated as medium. 



Forms of Fertilizer Materials. It is the common experience of 

 farmers and investigators that the different carriers of nitrogen, phos- 

 phorus and potassium behave differently on different soils, in different 

 seasons and with different crops. Most fruit and tobacco growers 

 recognize the difference in the different forms of potash although it is 

 not clearly understood why these differences occur. 



Under present fertilizer regulations dealers are required to state 

 only the percentage of the plant-food constituents in the fertilizers they 

 offer for sale. It would be a wise provision if in addition to this they 

 were required to state the source of the constituents as well as the per- 

 centage. This is especially important as relates to nitrogen, which varies 

 widely in its availability, depending on its source. Many materials 

 containing essential elements are nearly worthless as sources of plant 

 food because the form is not right. Plants are unable to make use of 

 these materials because they are unavailable. Materials that do not 

 show wide variation in composition and in which the constituents are 

 practically uniform in their action, may be regarded as standard in the 

 sense that they can be depended upon to furnish practically the same 

 amount and form of a constituent wherever secured. Among such standard 

 materials may be considered nitrate of soda, sulphate of ammonia, acid 

 phosphate, muriate of potash, sulphate of potash and carbonate of potash. 



Relative Value of Fertilizer Ingredients. A practical point, and one 

 of importance to the farmer, is a reliable estimate of the relative value 

 and usefulness of the various products that enter into commercial fertil- 



