EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE, rive 
Not only was no comparison made between raw rock phosphate 
and the acidulated phosphates in this experiment, but no strict com- 
arison can be made between the plots treated with raw rock and those 
receiving bone meal, as in every case the two forms of phosphoric 
acid were used in conjunction with different fertilizers. The plots 
(both drained and undrained) which were treated with raw rock, 
manure, and a legume, however, showed substantial increases in yield 
- over those receiving only manure and a legume (except the drained 
corn plot in 1908, and the undrained oat plot in 1909). 
Mitler, Hutchison, and Hudelson? described four other experi- 
ments in which an attempt was made to study the relative fertilizer 
merits of raw rock phosphate and steamed bone meal in four-year 
rotations. The experiments were conducted on four series of plots 
so that each crop was grown every year. ‘The work was carried on at 
the following places: Jasper County, near Carthage; on the High . 
Hill experiment field, Montgomery County; on the Hurdland ex- 
periment field, Knox County; and on the Laclede experiment field, 
Linn County. | 
The Jasper County experiment? was conducted for a period of 
only four years and is therefore not repeated in detail but the indi- 
cations were that raw rock was quite effective when used in conjunc- 
tion with manure, the average yield of these plots leading all others, 
with the exception of the average yield of wheat on the plots treated 
with lime, bone meal, and potash. In this experiment also there was 
no comparison made between acid phosphate and the less soluble 
forms of phosphoric acid. 
The experiment field at High Hill,3? Montgomery County, Mo., is 
located “on a slight ridge which slopes considerably to the west 
from the center of the field, with the east one-fourth sloping slightly 
to the east. In neither case is the fall sufficient to cause the land to 
wash badly.” The field had been cropped to corn and oats for about 
twenty-five years, being in corn about two-thirds of the time. The 
soil is a gray silt loam grading into a dull gray silt below, which 
becomes heavier with depth, and interferes somewhat with the under- 
drainage. The soil is low in nitrogen, but fairly well supplied with 
phosphoric acid and potash. The plots were one-fifth acre each, 
and were laid out lengthwise across the slope. The experiment 
which was begun in 1907 was continued to 1913 (seven years) in a 
four-year rotation of corn, oats, wheat, and clover, but some of the 
crops were apparently not weighed. During the last year of the 
1Mo. Agr. Expt. Sta., Buls. Nos. 119, 126, 127, and 128. 
2Mo. Agr. Expt. Sta., Bul. No. 119, pp. 3-17 (1914). 
® Mo, Agr. Expt. Sta., Bul. No. 126, pp. 326-333 (1915), 
