FERTILIZER ANALYSIS 277 



There are two tests for telling whether or not a soil is 

 acid, but not how acid. One is by the use of blue litmus 

 paper. A strip of blue litmus paper is placed in the bottom 

 of a beaker or tumbler and on top of this a piece of filter 

 paper or clean white blotter cut to fit the bottom of the 

 vessel. The soil to be tested is added until the dish is half 

 full, and is then soaked with pure water. Another beaker 

 or tumbler is prepared the same way but no soil added. 

 This is to test the paper and water for acids. If the litmus 

 paper in the beaker containing the soil has turned red 

 after standing an hour, the soil is acid, the degree of acidity 

 depending on the amount and rapidity of coloration. At the 

 same time the litmus paper in the beaker containing no 

 soil must remain blue. If it turns red the paper or water 

 contains acid and a fresh test must be made using different 

 paper and water. 



Another test is to add two or three ounces of soil to a 

 beaker or tumbler full of dilute ammonium hydroxide, 

 made by mixing one part of strong ammonia with five parts 

 of pure water. After standing some time an acid soil will 

 yield a brown or black color to the liquid, due to the solubility 

 of the humus acids in ammonium hydroxide (Section 124). 

 A neutral or alkaline soil will not yield a color to the liquid 

 beyond that which will be imparted to it by the fine soil 

 particles held in suspension. 



212. Fertilizer Analysis. — The total amount of plant food 

 in fertilizers can be determined accurately and, with the 

 possible exception of nitrogen, the available material can 

 also be determined. In buying a fertilizer a farmer wants 

 something ordinarily which is quickly available to his crops. 

 State laws now require fertilizer manufacturers to give the 

 analvsis with everv fertilizer. This analysis usuallv consists 

 of total nitrogen; water soluble, citrate soluble, insoluble, 

 and total phosphoric acid; and water soluble potash. 



There are methods which attempt to determine available 

 nitrogen, but except for the determination of nitrates and 

 ammonia which are satisfactory, there are no reallv e;ood 

 methods. As a matter of fact, however, a determination 

 of total nitrogen is usually sufficient. The use of certain 



