SOILS AND FERTILIZING MATERIALS 35 



three tons of a low-grade fertilizer, one ton of 

 the former containing the same amount of plant 

 food contained in three tons of the latter; be- 

 cause, in making the latter, three times as many 

 packages or bags are required and three times as 

 much freight must be paid all for the same amount 

 of plant food. 



Fertilizers cannot, as a rule, be in too finely 

 powdered condition nor can they be too dry. 

 With many materials, bone, for example, the 

 availability as plant food is directly dependent 

 upon the fineness of division. Excessive moisture 

 in fertilizer is undesirable on several grounds. 

 First, the larger the amount of moisture, the 

 smaller will be the amount of plant food in a ton. 

 Second, excess of moisture causes the particles 

 to stick together, and is likely to result in caking 

 and clogging when used in drills. Third, an excess 

 of moisture favors the decomposition and loss of 

 nitrogen in many forms of organic matter. This 

 is shown by the fact that some fertilizers give off 

 a very offensive odor if allowed to become damp, 

 while they are comparatively free from disagree- 

 able odors if they are thoroughly dry. A strong 

 odor in a fertilizer is an indication that organic 

 matter is decomposing and nitrogen is being lost. 



Materials which are readily soluble can be scat- 

 tered over the surface. After the first rainfall 

 they distribute themselves throughout the soil 

 very completely and uniformly. Such materials 

 are nitrate of soda, sulphate of ammonia, soluble 



