INSPECTION OF COMMERCIAL FERTILIZERS 57 



Citratus Precipitated Phosphate. This product is manufactured by the 

 IJay Chemical Co., New Orleans, La. This firm employs raw mineral phosphate 

 in place of bone, re-preeipitating the dissolved jihosphate by neutralizing with 

 milk of lime solution. Precipitated phosphate is not greatly unlike i)recii)itated 

 bone, but contains somewhat more iron and aluminum and somewhat less cal- 

 cium, as will be seen in the tabulated results of chemical analysis. 



Reform Phosphate. This product is manufactured by the Reform Phosphate 

 Corp., New York, N. Y., by treating mineral phosphate with sulfuric acid in 

 amoimts very much under the usual quantity employed in making superphos- 

 |)hate. By the laboratory methods Reform Phosphate tests very much less in 

 so-called available phosphoric acid than does ordinary superphosphate. The 

 producers claim, however, that the phosphoric acid is readily available to growing 

 plants. 



Finely Ground Rock Phosphate. This product is washed and finely ground 

 natural phosphate, sold widely in this country, and registered in Massachusetts 

 by the Ruhm Phos]ihate & Chemical Co., Mt. Pleasant, Tenn. 



Superphosphate. This is a typical 16% Superphosphate selected at random 

 from the large number of superphosphates sampled by our inspectors during the 

 1929 season. It was selected as one of the standards by which to measure the 

 availability of the phosphoric acid in the other phosphates under study. 



Triple Superphosphate. This material was secured from trade channels 

 and was selected as one of the standards for comparative purposes. 



The following table shows the general chemical composition of each product 

 imder experiment. 



Outline of the Experiment. 



The experiment was conducted in three series: I, with minimum phosphoric 

 acid; II, with optimum phosphoric acid; and III, with the raw mineral phosphates, 

 using double the optimiun phosphoric acid. In addition check pots with in- 

 creased amounts of nitrogen and potash were included to show that these two 

 elements were not limiting factors in the growth of the croj). 



Each pot received 36 pounds of air-dried soil secured from the west end of Plot 

 7, North Soil Test, which has had yearly applications of nitrogen, potash and lime, 

 but no phosphoric acid since 1890. The soil showed 0.085 y.er cent acid-soluble 

 phosphoric acid. 



The fertilizers used in the experiment were mixed with the entire amoiuit of 

 soil in each pot. The pots were filled, thoroughly moistened, and allowed to 

 stand two weeks before seeding. Each pot received 1.143 grams of phosphoric 

 acid for the minimum series, and double this amount for the optimum, calculated 

 in each case from the content of total phosphoric acid as shown l)y chemical 

 analysis. 



Fine ground limestone was ap]ilied at the rate of 16.33 grams per pot, which 

 was a little more than sufficient to produce a neutral soil, as measured by the 

 Veitch Method. The nitrogen was supplied by 35.76 grams of dried blood and 

 10.54 grams of nitrate of soda, the total being equivalent to 1,142 pounds of 

 nitrogen per acre. The potash was derived from 15 grams of sulfate of potash- 

 magnesia, 8.20 grams of high grade sulfate of potash, and 16.33 grams of muriate 

 of potash, the total equivalent to 2,880 pounds of i)otassium oxide per acre. 

 Wherever the phosphoric acid fertilizers carried either nitrogen or potash, a 

 modification was made in the regular application of these two ingredients, so as 

 to insure the same amount to each i)ot. 



Water was supplied by both subirrigation and surface application in amounts 

 representing 50 per (!ent of the water-holding capacity of the soil. The pots were 

 balanced twice each week during the growing season. 



