32 MANUFACTURE OF FERTILIZING MATERIALS 



potash and phosphoric acid present. When such 

 crops as corn, cabbage, grass, potatoes, etc., have 

 a luxuriant, healthful growth, an abundance of 

 potash in the soil is indicated; also when fleshy 

 fruits of fine flavor and texture can be successfully 

 grown. On the contrary, when these plants fail 

 o r a luxuriant growth, or are very low grade in 

 quality, it is certain indication that potash is 

 lacking. When a soil produces good, early matur- 

 ing crops of grains with plump and heavy kernels, 

 phosphoric acid will not generally be found 

 deficient in the soil. 



In order to ascertain with greater certainty 

 what food elements are lacking in the soil, care- 

 ful experiments would have to be carried out on 

 the soil and crops, by applying different kinds 

 of fertilizing materials in different combinations, 

 using, for example, potash compounds in one com- 

 bination, phosphoric acid compounds in another, 

 nitrogenous materials in another. Then different 

 combinations can be made on other portions of the 

 crop. Some portions of the field can be left with- 

 out application of any kind. The result can then 

 be studied in the yield of crop. In carrying on 

 such field tests, several difficulties may be met. 

 The season may frequently be such as to interfere 

 seriously with the favorable action of the fertilizing 

 materials applied. Thus, a severe drought may 

 counteract all other conditions and prevent a 

 satisfactory yield. The difference of mechanical 

 condition of the soil on the same farm or even in 



