NITROGEN BEARING FERTILIZERS 325 



of soil organisms acting through a very long period, and 

 leaving the product finally in the form of sodium nitrate 

 that has crystalized out of solution in which it has some- 

 time been held. The crude salt is purified by crystalli- 

 zation, and, as put upon the market, contains about 

 96 per cent sodium nitrate, or about 16 per cent of nitro- 

 gen, 2 per cent of water, and small amounts of chlorides, 

 sulfates and insoluble matter. The cost of nitrogen in 

 this form is from fifteen to eighteen cents per pound. 



On account of its easy availability, sodium nitrate 

 acts quickly in inducing growth. For this reason it is 

 used much by market gardeners, and for other purposes 

 when a rapid growth is desired. It is the most active 

 form of nitrogen. A light dressing on meadow land in the 

 early spring assists greatly in hastening growth by fur- 

 nishing available nitrogen before the conditions are 

 favorable for the process of nitrification. On small 

 grain it serves a similarly useful purpose where the soil 

 is not rich. 



Owing to the fact that it is not absorbed by the soil 

 in large quantities, it is easily lost in the drainage water; 

 for which reason it should only be applied when crops 

 are growing upon the soil, and then only in moderate 

 quantity. 



The continued and abundant use of sodium nitrate 

 upon the soil may result, through its deflocculating 

 action, in breaking down aggregates of soil-particles, 

 thus compacting and injuring the structure. This effect 

 is attributed to the accumulation of sodium salts, par- 

 ticularly the carbonate, as the sodium is not utilized 

 by the plant to the same extent as is the nitrogen. 



