126 NATURE STUDY REVIEW (10:4— April, 1914 



always remember that the lowest stated amount of available nitro- 

 gen," phosphoric acid, and potash are the only materials to be con- 

 sidered in a guaranteed analysis, although other statements 

 frequently occur in the printed analysis of a fertilizer. 



State Experiment Stations of State Departments of Agriculture 

 furnish bulletins giving analyses of various commercial fertilizers 

 on the market. By means of these bulletins the actual value of 

 any fertilizer may be readily estimated if the market price of the 

 "essential ingredients" is known. 



Home Mixing of Fertilizers 



Explanation: 



In the previous study of commercial fertilizers a difference 

 was foimd between the dealer's price and the actual value of plant 

 foods contained in the mixture. When this difference seems to 

 be too great the ingredients may be bought separately and mixed 

 at home. When several farmers club together and buy the sepa- 

 rate ingredients in quantity a considerable saving may be made. 

 Nitrogen, phosphoric acid, and potash should be bought in con- 

 centrated form. For example, phosphoric acid, in an acid phos- 

 phate having 12 per cent, phosphoric acid, costs about seven 

 cents a pound; while in an acid phosphate having 16 per cent 

 phosphoric acid it costs a fraction over five cents a pound. 



The amount of each ingredient desired should be accurately 

 calculated before mixing. 



Directions: 



All calculations are based upon the percentages of nitrogen, 

 phosphoric acid, and potash in the materials purchased. The 

 following are the percentages of the most common forms of 

 fertilizing materials: nitrate of soda, 16 per cent nitrogen; 

 sulfate of ammonia 20 per cent nitrogen; dried blood, 10 per 

 cent nitrogen; acid phosphate 14 to 16 per cent phosphoric acid 

 (the guaranteed analysis will give the exact percentage) ; muriate 

 of potash, 50 per cent potash (the guaranteed analysis will give 

 the percentage of potash in other forms like sulfate of potash, etc. 



The amoimt of nitrogen in a ton (2000 pounds) of nitrate of 

 soda is found by taking 16 per cent of 2000. (2000 x .16 = 320). 

 A ton of nitrate of soda will, therefore, contain 320 pounds of 

 nitrogen. 



