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 
Whe Ohio experimental work. 
PENNSYLVANIA. 
The Pennsylvania Experiment Station in 18831 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 cibecqucner | 
received the same fertilizer treatments are given. 
: Taste LVIII.—Average yield of oats on various plots of experiment field before 
application of fertilizer. 
Yield per 
Plot letter. acre of 
oats, 1883. | 
| 
Bushels. 
mean GiGS ee kee” 45. 94 
Brands. fs 5 3. soso eaen sce 46. 56 
Crndle* 35S See 49, 38 
DSON Gs. ee ese oe oecemecos 49.06 
rand Ke. es ose aces cee 54. 
PAT eee cine eae 52. 81 
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 
1Pa. Agr. Expt. Sta., Ann. Rept. for 1884, pp. 33-35 (1885). 
2Pa. Agr. Expt. Sta., Ann. Repts. for 1884 (1885) ; 1886 (1887) ; 1888 (1889) ; 1889 
(1890) ; 1895 .(1896). 
56841°—Bull. 699—18——7 : 
