447 



THE PURCHASE OF ARTIFICIAL MANURES. 



While certain artificial or, as they are sometimes called,, 

 chemical or light manures are to some extent applied in 

 autumn, it is in spring* that farmers lay in the bulk of their 

 supplies, and therefore it seems appropriate that a few sug- 

 gestions should be offered at this season in regard to their 

 economic purchase. 



There are three substances, and only three, that are valued 

 in artificial manures, namely, nitrogen, phosphates, and 

 potash. According, therefore, to the greater or less quantity 

 of one or other of these substances the value of the manure 

 will rise or fall. Some manures contain only one of these 

 substances — tor instance, nitrate of soda and sulphate of 

 ammonia contain only nitrogen ; superphosphate, precipitated 

 phosphate, and basic slag contain only phosphate ; and 

 kainit, sulphate of potash, and muriate of potash contain 

 only potash — while other manures hold two substances of 

 value, as in the case of bones, which furnish both nitrogen 

 and phosphates, or saltpetre (very seldom used, however, as 

 a manure), which supplies both nitrogen and potash. Only 

 one class of so-called artificial manure, namely, Peruvian or 

 other similar guano, contains an important amount of all 

 three substances. 



In price lists nitrogen is frequently expressed as ammonia. 

 The relationship between the two substances is, however, a 

 very simple one, and need occasion no difficulty or un- 

 certainty : 17 lbs. of ammonia always contain exactly 14 lbs. 

 of nitrogen, or, what is the same thing from the farmer's 

 point of view, 14 lbs. of nitrogen are the equivalent of 17 lbs. 

 of ammonia. If, therefore, a sample of, say, " corn manure " 

 is offered as containing 4*5 per cent, of ammonia, this is the 

 same as saying that it contains 37 per cent, of nitrogen. 



