85 



proportion of nitrogen varies from 9 to 15 per cent, and 

 practical field experiments show that this element, in this 

 form, is readily and quickly available for the use of the 

 plant. 



The chief mineral forms of nitrogen of importance are sul- 

 phate of ammonia and nitrate of soda, though nitrate of pot- 

 ash and muriate of ammonia are also met with occasionally 

 in the fertilizer trade. The supplies of nitrate of soda are 

 obtained chiefly from the nitrate beds of Chili and Peru, 

 and the refined product has of recent years had quite a 

 large consumption in this country. It contains 15 to 16 

 per cent, nitrogen in a highly available form and is em- 

 ployed in the preparation of high grade fertilizers, and also 

 as a top dressing for grains, grasses, etc. 



Sulphate of ammonia is largely prepared from the am- 

 moniacal liquors of gas works, the crude liquor being neu- 

 tralized with sulphuric acid and evaporated to dryness. 



This substance is the most concentrated commercial form 

 of nitrogen which is found, in general, upon the markets, 

 and is used in the manufacture of complete fertilizers rich 

 in nitrogen, or else is employed as a top dressing for cer- 

 tain crops. 



For this latter purpose, however, both of the above min- 

 eral foi-ms of nitrogen must be applied with great caution, 

 since by virtue of their easy solubility, they are readily 

 leached from the surface soil, especially if the subsoil is at 

 all permeable. 



(3.) POTASH MANURES. 



The manures of this class which meet with the largest con- 

 sumption, either for direct application to the soil or as in- 

 gredients of mixed goods, are the crude potash salts from 

 the German salt deposits. The chief forms in which the 

 potash is found in the crude commercial salts are the sul- 

 phate and muriate (chloride), the latter form containing the 

 higher proportion of potassium. Kainite, another product 

 of the German mines, consists of potassium sulphate, mag- 



