EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 



33 



While it is stated that raw roCk phosphate was applied at the rate 

 of 1 ton per acre at the beginning of the experiment, it is not clear 

 if there were any subsequent applications during the remaining six 

 years of the experiment. No other commercial fertilizers were em- 

 ployed in this test; therefore the data allows no comparison of the 

 relative values of the different phosphates. 



All of the«*plots of this experiment field, with the exception of two, 

 received applications of organic matter either in the form of crop 

 residues or as farm manure. 



In Table X the results obtained on eight plots of each series are 

 given. 



Table X. — Average vields per acre from ttvo series of plots, Auburn field 



(1905-1911). 



Treatment. 



Corn, 7 

 crops. 



Oats, 3 

 crops. 



Clover, 2 

 crops. 



Raw rock phosphate 



Check 



Average gain for raw rock 



Bushels. 

 51.9 



46.2 



Bushels. 

 45.3 

 38.2 



5.7 



7.1 



2.16 

 1.66 



In commenting on this experiment Hopkins and his coworkers 

 state that " on the whole, the data from favorable seasons strongly 

 indicate a cumulative or increasing effect from the phosphate treat- 

 ment, as we have reason to expect and as is shown in the latest crops 

 of corn, oats, and clover, the increase amounting to about 25 per 

 cent for oats, 34 per cent for corn, and 48 per cent for clover." 



Hopkins ^ also published a paper in 1912 entitled " Shall We Use 

 Complete Commercial Fertilizers in the Corn Belt?" in which he 

 quotes the work of the Indiana and Ohio Experiment Stations with 

 a view to showing that complete mixed fertilizers are inferior and 

 much more expensive than the simple phosphate carriers, and that 

 raw ground rock is the most economic form of phosphoric acid. No 

 data from the Illinois Experiment Station farms are contained in 

 this circular. 



In 1913 Hopkins ^ published a paper entitled " Bread from Stones," 

 which consists of a description of an impoverished farm in southern 

 Illinois which the author has made productive by the so-called Illi- 

 nois system of permanent fertility. The particular tract considered 

 in this paper is a 40-acre field which had been agriculturally aban- 

 doned for five years prior to the experiment. During the 10 years 



56841^ 



iJll. Agr. Expl Sta., Circular No. 165 (1912), 

 2 111. Agr. Expt. Sta., Circular No. 168 (1913). 

 -Bull. 699—18 3 



