46 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
well above those of the checks. In this experiment the raw-rock plots 
gave average yields comparing favorably with those treated with acid 
phosphate. 
The writers feel, however, that the method of application used in 
these experiments hardly admits of a fair comparison of the relative 
merits of ground raw rock and acid phosphate. Nearly three times 
the amount of money was invested in raw rock during the 10 years as: 
in acid phosphate. This means that in order to show a profit com- 
paring favorably with that obtained on the acid-phosphate plots 
the increases in yield from raw-rock plots must be three times as 
great. On a field showing little or no response to phosphate treat- 
ments (such as the Littles field) it appears to the writers unwise to 
attempt to compare the two forms of phosphoric acid when the rock- 
phosphate plot was so heavily handicapped. Considering now the 
Scottsburg experiment, the only instance where there is any signifi- 
cant difference shown between the yields of the plots receiving the 
two forms of phosphoric acid is in the corn crop, where the average _ 
yield of the raw-rock plot was considerably greater than that of the 
plot treated with acid phosphate. | 
Four other experiments with raw rock phosphate undertaken by the 
Indiana station are described in this same paper, but none of them 
cover a period of over four years, so they do not warrant detailed 
- discussion. 
The work of the Indiana station on the whole, while not conclusive, 
gives evidence of increased crop yields resulting from applications of 
raw rock phosphate. Under the conditions of the experiments any 
attempt to form conclusions concerning the relative merits of raw 
rock and acid phosphate seems unwarranted. 
< 
=} 
4 
73 
ry 
KENTUCKY. ¢ 
: 
The first data of the Kentucky station pertaining to the use of raw 
rock phosphate as a fertilizer were published in 1899.1. They con- 
sisted of the results obtained from a one-year experiment with 
various phosphate carriers on wheat. 
The same cooperator continued the experiment the following year,? 
but employed a different field and discontinued the application of 
ground rock phosphate. The results of this experiment are not re- 
peated here. 
{In 1912 the Kentucky station in cooperation with the State Geo- 
logical Survey published a paper® containing the results of three 
series of pot experiments with a yellow silt loam of rather low 
phosphate content. In series 1 and 3, pots of 4 gallons capacity were | 
Hidguyhiaet 
iKy. Agr. Expt. Sta. Bull. No. 83, pp. 35-38 (1899). if 
2Ky. Agr. Expt. Sta., Bul. No. 89 (1900). 
®Ky. Agr. Expt. Sta., Bul. No. 162 (1912). 
