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 Ihose 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 floats 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. 



lOhio Agr. Expt. Sta., Buls. Nos. 258, 273, 286. 

 «OMo Agr. Bipt. Sta., Bui. No. 260. 



