84 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
prior to 1913, in which year.the results reported were obtained, the 
field was cropped with a 6-year rotation, including 1 year each of 
corn, oats (or cowpeas), and wheat, and 3 years of meadow and 
pasture with clover and timothy. 
The figures obtained seem very favorable to the use of heavy appli- 
cations (2 tons) of raw rock phosphate, but they are the yields off 
only one year. A comparison of the yields obtained therefore with 
and without the addition of raw rock phosphate is probably justified, ~ 
although the land treated with phosphate rock received twice as 
much limestone as the plot on which no phosphate was applied. It 
is possible that the additional amount of lime which this tract received 
had considerable influence on the large increase in yield. 
In the fall of 1913 Hopkins, Mosier, Pettit, and Fisher? reported 
in detail nine-year results of an experiment begun at Galesburg, I1., 
in 1904. The soil of this experiment field is the brown silt loam 
prairie soil of the Upper Llinois glaciation. _The field was divided 
into three series of plots, each series containing 20 plots of one-fifth - 
acre each. A six-year rotation was followed. The previous history 
of the experiment field is not given. 
At the beginning of the experiment limestone was applied to the 
first 15 plots of each series at the rate of 1,300 pounds per acre, and 
again to tke same plots in either 1912 or 1913 at the rate of 4 tons per 
acre. In 1904 the first applications of raw ground rock phosphate 
were made, but the regular plan of this experiment which was to 
apply 14 tons per acre of raw ground phosphate rock every six years 
before plowing for corn was not fully underway on all series of 
plots until 1906. One hundred pounds of potassium sulphate per | 
acre was applied annually. 
It was planned to study the use of phosphate rock, both in grain | 
farming and live-stock farming. In the grain-farming system crop 
residues are returned to the various plots in proportion to the pro- 
duction of each and in the live-stock system all produce (or its equiva- 
lent) is used for feed and bedding and the manure returned to the 
plots in proportion to their yields during the preceding rotation. 
In this particular experiment, however, these two systems were not 
in operation on all series until 1911 and 1912. The average yields 
of the various crops during the nine years of the experiment are given 
in Table XI. | 
2Tll. Agr. Expt. Sta., Soil Rept. No. 7 (1913). 
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