280 SOIL AND FERTILIZER ANALYSIS 



comparative work than for practical application to a single 

 soil. The use of blue litmus which turns red in an acid soil, 

 and of ammonium hydroxide which dissolves dark organic 

 acids from acid soils are tests which are easily applied and 

 of value as qualitative tests. 



Fertilizer analysis determines the amount of the various 

 plant foods present in fertilizers. The methods are accurate. 

 The results are expressed as total nitrogen ; total, water solu- 

 ble, citrate soluble, and insoluble phosphoric acid; and water 

 soluble potash. There is no very good method for available 

 nitrogen. Water and citrate soluble phosphoric acid are 

 together termed available phosphoric acid; and of course 

 water soluble potash is available. Other expressions may be 

 used in statins: the results of a fertilizer analysis but those 

 mentioned are in universal use and are easily understood. 

 Other terms only tend to confuse. 



REFERENCES 



Hilgard. Soils. 



Van Slyke. Fertilizers and Crops. 



