Sources of the Fertilizer Elements. 



Nitrogen : This element can be supplied in two 

 different ways. The first and cheaper of these is to grow 

 leguminous crops like alfalfa, clover or cowpeas on the land. 

 These plants have the power of extracting nitrogen from the 

 air, and of accumulating it. By then turning the crops under, 

 either wholly or in part, all or the greater portion of this 

 nitrogen is saved. Moreover, in this way we do not only sup- 

 ply nitrogen to our land, but incorporate with it that indis- 

 pensible organic material necessary for the formation of 

 humus. Humus is essential in the conservation of the soil 

 moisture. 



The second way of supplying nitrogen is by adding it in 

 the form of some commercial, nitrogenous fertilizer, like 

 nitrate of soda, sulfate of ammonia, cyanamid, dried blood, 

 cotton seed meal, etc. If nitrogenous fertilizers must be 

 bought, it will be best in the West to use those which have a 

 high percentage of nitrogen, in order to save freight. 



Phosphoric Acid: There are several forms in which 

 this fertilizer element can be supplied, Some phosphate 

 fertilizers, such as acid phosphate and dissolved bone are 

 easily soluble and can be utilized immediately by the plants. 

 Others are less available and their assimilation by the crop is 

 much slower than in the case of the first two. Among these 

 fertilizers we mention Thomas slag and bone meal. The 

 least available of the common phosphate fertilizers is ground 

 rock phosphate; this is quite insoluble and it is effective only 

 if applied together with large quantities of stable or green 

 manure. The acids formed by the decomposition of the 



