USE OF PHOSPHORUS IN DIFFERENT FORMS 263 



"Insoluble South Carolina phosphate rock produced a higher total average 

 yield than dissolved South Carolina rock. 



"Florida soft phosphate is chiefly an aluminum-iron phosphate which 

 occurs in large quantities deposited in many parts of that state. It is not well 

 adapted to treatment with acid for making soluble phosphates, as the aluminum 

 and iron make a sticky mass which is hard to dry and keep in a good mechan- 

 ical condition. The Florida soft rock has been largely used as a fertilizer in its 

 natural condition in some parts of that state on the light, sandy land, giving 

 good results. When used in this way, there has been applied at the same 

 time heavy dressings of the native mucks from the swamps and lakes. This 

 muck furnishes nitrogen as well as the much-needed organic matter. In order 

 to have a complete fertilizer, there is also applied some German potash 1 salt. " 



The Pennsylvania Experiment Station has reported the results 

 of an experiment extending over twelve years (1884 to 1895), in 

 which four different kinds of phosphorus were used in a four-year 

 rotation of corn, oats, wheat, and hay (clover and timothy). Only 

 one field was employed, so that each crop was grown only three 

 times during the twelve years. 



The four forms of phosphorus were (i) acid phosphate made from 

 bone black, (2) " reverted " phosphate made by mixing equal 

 weights of dissolved bone black and quicklime twelve hours before 

 application, (3) fine-ground bone meal (containing 8 pounds of 

 nitrogen and 35 pounds of phosphorus in 300 pounds of bone), 

 and South Carolina ground raw rock phosphate. The amounts 

 applied per acre in each four years were 28 pounds of soluble and 

 " reverted " phosphorus, and 35 pounds in bone and raw rock. 



No special provision was made for supplying decaying organic 

 matter, but 94 pounds of nitrogen (102 pounds on the bone-meal 

 plots) and 83 pounds of potassium (in potassium chlorid) were 

 applied per acre, each four years, to all phosphorus plots and also 

 to two comparison plots that received no phosphorus. In addition, 

 there were two plots that received no application of plant food. 

 The entire experiment was carried on in duplicate. One half of 

 the fertilizer for the rotation was applied to the corn crop and the 

 other half to the wheat crop. 



Table 430 gives the average yields of all products harvested dur- 



1 Most peat soils and some sands are extremely deficient in potassium, and it 

 is also difficult to liberate potassium that may exist locked up in coarse sand grains, 

 as suggested, for example, by the Illinois experiments at Momence, p. 474. C. G. H. 



