Supplying Soil Needs 



173 



FIG. 134. A sodium nitrate refinery in the desert of northern Chile. Chile 

 once fought a war with Peru and Bolivia for the control of the nitrate fields. 



A nitrogen fertilizer should be put into the soil at the when to 

 time of planting or just before planting, so that the ^ ly ^ n 

 plants may secure their nitrogen while they are young, fertilizer 

 If the nitrogen is given after the crop is partly grown, 

 it will stimulate new growth of leafy material and the 

 fruit will be late in maturing. On the other hand, 

 if it is applied too early it is liable to be washed out 

 and lost. 



The simplest form of nitrogen fertilizer is a substance Nitrate of 

 called "saltpeter" or "nitrate of soda." (Exp. 2.) 

 It looks very much like common salt, but it contains a 

 large amount of nitrogen (one sixth of its total by weight). 

 Unfortunately this salt is becoming very scarce. The 

 only very large supply of it is found in northern Chile 

 along the "rainless coast" (Fig. 134). The sodium 

 nitrate, or " Chile saltpeter," lies in beds from a few inches 



soda 



