EXPEEIMEISTTAL WOEK WITH EAW ROCK PHOSPHATE. 71 



the lowest average yields were obtained from the plots treated with 

 the natural phosphates of Arkansas, Florida, Tennessee, and South 

 Carolina. 



It seems questionable to the writers, however, if this method of 

 grouping the various phosphates is altogether fair. By referring 

 to Table XL it will be seen that the yields from the Florida soft 

 phosphate plot were in man} instances poor when the yields from 

 the other raw-rock plots, particularly the South Carolina rock plot, 

 were good, Bj grouping Florida soft phosphate with the - South 

 Carolina and Tennessee phosphates the average yield for raw rock is 

 seriously affected. 



Neither does the placing of dissolved bone meal, acid phosphate, 

 and dissolved bone black in one group appear quite fair, since the 

 first-mentioned material contains appreciable quantities of nitrogen, 

 and in nearly every instance the yield of this plot exceeded the other 

 soluble phosphate plots by a considerable margin. 



In order that the reader may obtain a clearer idea of the value 

 of each fertilizer treatment the writers have compiled the following 

 table from the reports of this work as given from year to year 

 during the entire period of the experiment. Full details of yields, 

 however, are not given in the reports for the years 1898, 1899, 1900, 

 1905, 1908, 1909, 1911, and 1912. 



