344 THE PRINCIPLES OF SOIL MANAGEMENT 



A ton of low-grade fertilizer may contain 500 or 600 

 pounds more inert material than a high-grade fertilizer, 

 upon which freight must be paid, and which must be 

 hauled from the station and spread upon the field. 



211. Fertilizer inspection. Some thirty states have 

 enacted legislation providing for the inspection and con- 

 trol of the sale of commercial fertilizers. Each package 

 of fertilizer must bear a certificate stating the percentage 

 of nitrogen, phosphoric acid and potash, and more or less 

 information in regard to the forms in which these are 

 held and their rates of solubility. This must be guaran- 

 teed to be correct by the manufacturer. 



The guarantee does not always state the percentage 

 of nitrogen (N), phosphoric acid (P 2 5 ), and potash 

 (K 2 0),but often uses other terms that imply the presence 

 of these substances, but so combined that the percentage 

 of the carrier is larger, as, for instance, ammonia, bone 

 phosphate and sulfate of potash. To convert one term 

 into another, factors have been devised which greatly 

 simplify the process. 



Per cent ammonia X .8235 = per cent nitrogen (N.) 

 Per cent nitrate of soda X .1647 = per cent nitrogen (N). 

 Per cent bone phosphate X .458 = per cent phosphoric acid 



(PA)- 



Per cent muriate of potash X .632 = per cent potash (K 2 0). 

 Per cent sulfate of potash X .54 = per cent potash (K 2 0). 



212. Trade values of fertilizers. It has been custom- 

 ary for the authorities charged with fertilizer inspection 

 in the states concerned to adopt each year a schedule of 

 trade values for nitrogen, phosphoric acid and potash, 

 in each of the various forms in which they appear in 



