94 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
An inspection of Table LV will show that here again very 
different conclusions may be drawn from the experimental data, 
depending on the method used in comparing the checks with the 
various fertilized plots. 
According to the Ohio method of comparison raw rock phosphate 
when applied alone at the rate of 320 pounds per acre gave some 
slight increases in yield, though not as great as the same quantity 
of acid phosphate. By the second method of comparison, however, 
practically no increase was obtained from such small applications 
of raw rock. 
Again, by the Ohio method of calculation, manured plots on which 
raw rock phosphate was applied at the rate of 1,000 pounds per acre 
as a top dressing gave an average increase in yield less than that 
obtained from plots receiving manure alone. According to the sec- 
ond method of comparison, however, the plots receiving such heavy 
applications of phosphate rock produced considerably greater yields 
than those receiving manure alone. There were no plots in this | 
experiment on which acid phosphate and manure were ‘used in 
conjunction. 
Another experiment with raw rock phosphate, using a rotation of . 
beets, oats, and clover, was begun by the Paulding County Experi- 
ment Station in 1911,' but since the data so far published on this 
experiment cover only three years or one complete rotation it is 
too early to draw any conclusions therefrom. 
In what are known as the “ Strongville experiments”? the Ohio 
station has made a comparison of the relative effect of lime and 
floats in a five-year rotation of corn, oats, wheat, clover, and tim- 
othy. 
The field used in this experiment is nearly level east and west, but 
slopes gently to the north. It was divided into four sections (A, 
B, C, and D) containing 40 plots of one-tenth acre each. The soil 
of the field is a heavy white clay naturally low in phosphoric acid, 
and had been employed in a fertilizer experiment under the same 
system of rotation for 12 years. After the introduction of the lime 
and ficats the applications of the other fertilizer materials were con- 
tinued as before, but each plot was divided into two parts, on one 
of which floats were applied and on the other ground limestone. 
The dressings have been 2 tons of limestone per acre on the south 
half of each entire section, and 1 ton of floats per acre on the north 
half, the applications being made on the corn crop only. The aver- 
age yields of the checks and the variously treated plots in each sec- 
tion from 1905 to 1912, inclusive, are given in Table LVI. 
1 Ohio Agr. Expt. Sta., Buls. Nos. 258, 273, 286. 
2Qhio Agr. Expt. Sta., Bul. No. 260, 
