EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 15 
with the yields from the plots receiving mixtures of acid phosphate 
and cottonseed meal, and in every case the phosphate-cottonseed-meal 
mixtures gave substantially greater yields than the cottonseed meal 
alone. 
The yields obtained in the cotton experiment, however, were more 
favorable to acid phosphate than to the raw rock, but the plots 
treated with the latter phosphate mixed with cottonseed meal gave a 
greater yield than those treated with cottonseed meal alone. 
It may be said that while these experiments give a very limited 
amount of data on the fertilizer value of raw rock phosphate they 
indicate that even light applications of this material when supple- 
mented with cottonseed meal may produce substantial increases in 
the yield of corn and cotton. 
Of the nine field experiments with raw rock shogeinae conducted 
by the Mississippi station only two were continued beyond four 
years. In these two the applications of the ground raw rock were so 
light that results can hardly be considered indicative of the value of 
this material. In practically all of the experiments, however, plots 
recelving raw rock phosphate, either alone or in combination with 
other fertilizer materials, have shown substantial increases over the 
check plots with which they were directly comparable. 
MISSOURI. 
The Missouri station advised the use of raw rock phosphate in 
19051 and 1910,? but it was not until 1914 that any data obtained 
from field work was published by this station. 
In an experiment described by Miller, Hutchison, Douglass, and 
Hudelson,? a study was made of the effect of various fertilizer treat- 
ments on both drained and undrained land in a four-year rotation 
of corn, oats, wheat, and cowpeas (with cowpeas grown and turned 
-as a catch crop between the regular crops of the rotation). 
The field selected for this experiment was a 10-acre tract of very 
level poorly drained prairie land lying one-half mile west of Van- 
dalia. The soil was a dark-gray silt loam 7 to 9 inches in depth un- 
derlain by a silty clay. The field was divided into two equal parts 
and one half tiled and the other half left untiled. Each half was 
then divided into seven plots of seven-tenths acre each, running cross- 
wise of the drained and undrained areas. The corresponding plots 
in each area were then treated as follows: Manure at the rate of 8 
tons per acre, and raw rock phosphate at the rate of 600 pounds per 
acre every four years before corn, bone meal 150 pounds per acre, 
and potassium chloride 50 pounds per acre, twice during a rotation. 
1Mo. Agr. Expt. Sta., Circular of Information No. 22, p. 25 (1905). 
2Mo. Agr. Expt. Sta., Bul. No. 84, p. 33 (1910) : Bul. No. 86, p. 91 (1910). 
3 Mo. Agr. Expt. Sta., Bul. No. 118, 448-475 (1914). 
