12 



Simple oe Mineral Manures. 



Besides the organic materials which have been discussed, we have a number 

 of other substances, generally of mineral or artificial origin, which are employed 

 is fertilizers. These may be divided into nitrogenous, phosphatic and potassic. 



Many of the organic materials already described contain variable quantities 

 of the chief manurial substances, but those about to be dealt with are as a rule 

 intended to supply only one important element of plant food. Their use makes it 

 possible for the farmer to apply one or more elements of plant food that may 

 be necessary on his farm, and thus obviates the need of purchasing other elements 

 vhich he may not require. 



NITROGENOUS FERTILIZEES. 



Although four-fifths of the atmosphere is nitrogen and thousands of pounds 

 of this element are over every acre of land, it is the most costly plant food 

 iubstance. As has been pointed out, the growing of leguminous plants makes it 

 possible for the farmer to gather some of this immense supply. Hence, the more 

 :he leguminous crops are introduced into the rotation, the more this free nitrogen 

 :s incorporated into the soil. Through this agency the soil may be enriched in 

 aitrogen, and every effort ought to be made to gather some atmospheric nitrogen 

 md thereby reduce the amount that has to be provided from other sources. 



The most important nitrogenous fertilizers are: nitrate of soda, sulphate of 

 immonia, and calcium cyanamid. These are all soluble in water, and should 

 oe used as a direct food to the plant and not to build up a reserve in the soil. 



Nitrate of Soda. 



Sodium nitrate (nitrate of soda. Chili saltpetre) occurs in enormous deposits in 

 Peru and Chili. It is found in rainless districts and comparatively near the 

 surface. The raw material is found beneath a covering of sand, gypsum, clay 

 ind gravel, which is usually removed with the aid of gunpowder. The crude 

 aaaterial thus exposed varies from a few inches to 12 feet in thickness and is 

 oroken up and carried to the refinery where it is purified by crystallization. 

 The material is then put up in sacks containing 200 pounds and in this foim 

 -s shipped to all parts of tha world. The product supplied for agricultural 

 purposes contains approximately 95 per cent, of real sodium nitrate and conse- 

 quently yields about 15.6 per cent, of nitrogen. Tt is extremely soluble and diffusible 

 and is at once available to plants, hence the greater part should be applied when 

 the crop is sufficiently grown to be capable of assimilating it, otherwise, since it is 

 aot retained by any constituent of the soil, considerable loss in drainage may 

 occur. 



Ammonium Sulphate. 



When organic nitrogenous substances are submitted to destructive distillation, 

 shat is, heated strongly without access of air, the nitrogen which they contain 

 is to a large extent expelled as ammonia. Therefore, when coal is heated by 

 destructive distillation in the preparation of coal gas the nitrogen which it con- 



