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EXPERIMENTAL WORK WITH RAW 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 
ouping the various phosphates is altogether fair. By referring 
o Table XL it will be seen that the yields from the Florida soft 
phosphate plot were in many instances poor when the yields from 
the other raw-rock plots, particularly the South Carolina rock plot, 
were good. By grouping Florida soft phosphate with the South 
Carolina and Tennessee phosplintes 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 mate 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 inargin. 
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. 
