88 — BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
The average yields of the various crops as given in Tables XIII 
and XIV show little or no benefit from the application of phosphate 
rock, and where the plots so treated do show an average increase 
for certain crops this increase is practically no greater than the 
difference between the yields of the check plots. In an experiment 
of comparatively short duration, however, it is hardly fair to the 
difficultly soluble material (such as raw rock phosphate) to average 
the results as has been done in the above tables, since the figures so 
obtained give no idea of the cumulative effect of the phosphate treat- 
ments. As a matter of fact in these experiments the average finan- 
cial returns from the raw-rock plots during the last two years 
were over twice as great as in the first three years, seeming to indicate 
that increasing amounts of organic matter and more thorough dis- 
tribution of the phosphate were having an important influence in 
rendering the latter more effective in the soil. The author also points 
out the facts that the wheat crop in 1912 was a failure throughout the 
State and that the droughts in 1913 and 1914 were probably more - 
severe than ever known in two consecutive years in the southern part 
of the State. 
In January, 1916, Hopkins, Mosier, Van Alstine, and Garrett? 
reported the results of a number of experiments with raw rock phos- 
phate which included 11 years’ work on the Rockford field and 4 
years’ work on the Mount Morris field. Raw rock phosphate was the 
only phosphate fertilizer used in these experiments except what was 
contained in the manure and crop residues returned to the land. 
The Rockford experiment field is located about 3 miles from the 
city of that name in Winnebago County, Ill. The soil of the field is 
described by the authors as a brown silt loam of the Iowan glaciation. 
No data are presented showing the relative fertility of the various 
plots nor is any previous history of the field given in this report. 
The field, however, was divided into four tracts, which were further 
subdivided into 20 plots of one-tenth acre each. A four-year rota- 
tion consisting of corn, corn, oats, and clover (with soy beans substi- 
tuted in case of failure of the latter) was begun in 1904, each crop 
being grown every year on one of the four series of plots. It was 
planned to practice both grain and live-stock farming systems on 
this field, but neither system was fully under way until the later 
years of the experiment. In 1905, however, a legume cover crop 
was turned under on the plots indicated in three of the series and in 
1908 a second growth of clover was turned under on the fourth series 
for the 1909 crop. Manure was applied on the plots indicated once 
at the rate of 4 tons per acre. Since 1909 it has been applied accord- 
ing to the live-stock farming system already described. Ground 
1111. Agr. Expt. Sta., Soil Rept. No. 12 (1916). 
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