EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 



97 



of crops, and that the efficiency of this material is increased by the 

 mixing or composting with organic matter. The data presented 

 by the Ohio Station, however, hardly appear to justify in the judg- 

 ment of the writers a definite conclusion concerning the relative 

 merits of raw rock and acid phosphate even under the conditions of 

 the Ohio experimental work. 



PENNSYLVANIA. 



The Pennsylvania Experiment Station in 1883 * undertook what 

 is probably the first recorded experiment with raw rock phosphate 

 conducted by the stations in this country. Since the work was car 

 ried on for a year only under conditions which were not controlled, 

 the results do not 'warrant repetition. 



A field experiment to test the fertilizer value of various phos- 

 phates was also begun by the Pennsylvania station^ in 1883, and 

 continued on the same field till the close of 1895, a period of 13 years. 



The field selected for this experiment has a slight and uniform 

 slope to the southeast. "The soil of the plots is a so-called lime- 

 stone clay formed from the decomposition of the surrounding and 

 underlying rock, which is largely a magnesian limestone. It has the 

 general appearance of a clayey loam. During 1880 and 1881 the 

 land was in grass (clover and timothy) and in 1882 in potatoes. 

 No manure was applied to either crop." In 1883, in an effort to de- 

 termine the uniformity of the field, it was divided into 12 plots of 

 one-twentieth acre each, and planted to oats without the application 

 of any fertilizer whatever. 



In Table LVIII the average yield of the plots which subsequently 

 received the same fertilizer treatments are given. 



Table LVIII. — Average yield nf oats on various plots of experiment field iefore 



application of fertiliser. 



Plot letter. 



Yield per 



acre of 

 oats, 1883. 



A and G 



Busheli. 

 45.94 

 46.56 

 49.38 

 49.06 

 54.06 

 52.81 



B and H 



C and I 



D and J 



E and K 







While it has been repeatedly pointed out that the yields obtained 

 with a single crop can not be taken as proof of the relative natural 



»Pa. Agr. Expt. Sta., Ann. Rept. lor 1884, pp. 33-35 (1885). 



«Pa. Agr. Expt. Sta., Ann. Repts. for 1884 (1885) ; 1886 (1887) ; 1888 (1889) ; 1889 

 (1890) ; 1895 (1896). 



56841°- -Bull. 699—18 1 



