ANALYSES OF FERTILIZERS 

 FALL SEASON, 1915; SPRING SEASON, 1916 



By B. W. Kilgoue, 

 W. G. Havwoou, J. Q. Jackson, E. S. Dewau, E. B. Haht and F. C. Wiggins. 



The analyses presented in this Bulletin are of samples collected by 

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

 Commissioner of Ac:ricultnrc, during fall months of 1915 and the spring 

 months of 1916. 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 

 fanner 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 Acid. — 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 the lime united 

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

 water-soluble phosphoric acid. 



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

 soluble phosphoric acid has a tendency to take lime from other substances 

 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 con- 

 sequence 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. 



