I. ANALYSES OF FERTILIZERS, 

 FALL SEASON, 1914; SPRING SEASON, 1915. 



By B. W. Kilgore, 

 W. G. Haywocd, J. Q. Jackson, E. S. Dewar, J. R. Mullen and E. B. Hart. 



The analyses presented in this Bulletin are of samples collected by 

 the fertilizer inspectors of the Department, under the direction of the 

 Commissioner of Agriculture, during fall months of 1914 and the spring 

 months of 1915. They should receive the careful study of every farmer 

 in the State who uses fertilizers, as by comparing the analyses in the 

 Bulletin with the claims made for the fertilizers actually used, the 

 farmer can know by or before the time fertilizers are put in the ground 

 whether or not they contain the fertilizing constituents in the amounts 

 they were claimed to be present. 



TERMS USED IN ANALYSES, 



Water-soluble Phosphoric A cic?.— Phosphate rock, as dug from the 

 mines, mainly in South Carolina, Florida, and Tennessee, is the chief 

 source of phosphoric acid in fertilizers. 



In its raw, or natural, state the phosphate has three parts of lime 

 united to the phosphoric acid (called by chemists tricalcium phosphate). 

 This is very insoluble in water and is not in condition to be taken up 

 readily by plants. In order to render it soluble in water and fit for 

 plant food, the rock is finely ground and treated with sulphuric acid^ 

 which acts upon it in such a way as to take from the three-lime phos- 

 phate two parts of its lime, thus leaving only one part of lime united 

 to the phosphoric acid. This one-lime phosphate is what is known as 

 water-soluble phosphoric acid. 



Reverted Phosphoric Acid. — On long standing some of this water- 

 soluble phosphoric acid has a tendency to take lime from other sub- 

 stances in contact with it, and to become somewhat less soluble. This 

 latter is known as reverted or gone-back phosphoric acid. This is 

 thought to contain two parts of lime in combination with the phosphoric 

 acid, and is thus an intermediate product between water-soluble and the 

 original rock. 



. Water-soluble phosphoric acid is considered somewhat more valuable 

 than reverted, because it becomes better distributed in the soil as a 

 consequence of its solubility in water. 



Available Phosphoric Acid is made up of the water-soluble and re- 

 verted ; it is the sum of these two. 



