NITROGEN GROUP OF FERTILIZERS 21 



nitrate can be easily absorbed by the plant, and nothing 

 is left behind in the soil, either good or evil. It therefore 

 is especially suited to conditions of drought or bad drainage 

 where undesirable salts accumulate and cannot be removed. 

 Ivike nitrate of soda, it is quite unsuitable for winter 

 application. 



Nitrate of Potash. — Nitrate of potash, or potassium 

 nitrate, is one of the earliest artificial manures. In the 

 vicinity of old village sites nitre earths are of comparatively 

 frequent occurrence, especially in India and Egypt. In 

 India the collection and working of these is an old-established 

 industr3^ The nitre earths, which have accumulated as 

 the result of the decomposition of organic nitrogenous waste, 

 are put into small pits with false bottoms and extracted 

 with a minimum possible quantity of water. The solution 

 obtained is then crystallized, and crude nitrate of potash 

 obtained. Both the original nitre earths and the waste 

 from this crude manufacture are used regularly for ordinary 

 manuring of crops. In some localities also, considerable 

 accumulations of nitrate of potash occur in the well waters, 

 and some of the districts in India which grow tobacco crops 

 are situated in areas where there are many nitre wells. 



The manufacture of pure nitrate of potash from the 

 above crude materials has been brought to such a state of 

 perfection that the waste contains very little potash or 

 nitric acid. 



Nitrate of potash is, of course, a very valuable manure, 

 as it contains two elements of value to the plant. When 

 added to the soil the potash combines with the clay and humus 

 and becomes fixed, and the nitric acid combines with the lime 

 in the soil (see also Potassium Manures, p. 37). 



Calcium Cyanamide. — The manufacture consists, firstly 

 in producing calcium carbide, which is made in an electric 

 furnace from lime and coke. The calcium carbide is then 

 heated, and nitrogen passed through it, when calcium 

 cyanamide and graphite are produced. The material i^ut 

 upon the market contains about 50 to 55 per cent, calcium 

 cyanamide, 25 to 30 per cent, lime 11 to 12 per cent, graphite, 



