9 



known as calcium cyanamide, made by heating- calcium carbide in air 

 from which oxygen has been removed, has very recently come into use. 

 It is the first successful attempt at gathering nitrogen directly from the 

 atmosphere and placing it in a commercial form on the market. Experi- 

 ments made in Europe show it to be about equal in value to nitrate of 

 soda, though a little slower in its action. Our own examination of this 

 substance shows that it contains about 20 per cent, of nitrogen and that 

 nitrification takes place somewhat slowly, the largest amount being avail- 

 able about the third week after application. 



Potash. The muriate of potash and sulphate of potash are the two 

 most important manures containing the one constituent, potash. The 

 former contains about 50 per cent, and the latter 53 per cent, of pure 

 potash. In both forms the potash is soluble and immediately available 

 as food to the plant. Wood Ashes are an important source of potash. 

 They contain only about one-tenth the percentage amount found in the 

 muriate and sulphate of potash, but they are one of our own natural 

 sources of potash and should be most carefully looked after. The potash 

 in wood ashes is soluble and in a good form of combination. The ashes 

 also contain some phosphoric acid and a large amount of lime. 



Phosphates. The most important phosphatic fertilizers are the 

 ground rock phosphates and the superphosphates, prepared from them. 

 Thomas phosphate, bone meal, bone ash, bone black, meat scrap, tank- 

 age, fish refuse, cotton seed hulls, horn dust, etc., are materials which 

 contain more than one plant nutrient and usually none of them in a very 

 readily available form. 



High-Grade Fertilizers. 



These fertilizers may be again divided into high-grade and low- 

 grade materials. Nitrate of soda, sulphate of ammonia, and dried blood 

 are, for example, standard or high-grade nitrogenous materials. They 

 are so classified, because they are fairly constant in composition and 

 furnish nitrogen in some constant and definite form, which will always 

 act the same under like conditions. Further, they are richer in nitrogen 

 than any other nitrogenous manures, and the element is immediately or 

 quickly available to the plant. Ground rock phosphates differ in this re- 

 spect from the above mentioned nitrogenous substances, because, in the 

 raw state, the phosphoric acid, tor which they are valued,. though present 

 in large quantities and quite constant and definite in its form of combina- 

 tion, is not available to plants. After it has been treated with sulphuric 

 acid and converted into superphosphate, it is high-grade, owing to the fact 

 that the phosphoric acid is now available. 



The various German potash salts, such as muriate of potash, sulphate 

 of potash, etc., are also high-grade, since the composition of each grade 

 and kind is practically uniform in its content of potash, which will 

 always act the same under all conditions, and since they are richer in 

 potash than any other potassic compounds suitable for making fertilizers. 



