96 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
Table LVI shows that on plots receiving no other fertilizer and 
also on those upon which nitrogen and potash but no soluble phos- 
phate was used, the portion treated with “ floats” gave consistently 
greater yields than that portion treated with ground limestone. The 
effect of the floats also appears to be cumulative. In regard to the 
plots receiving stable manure, little difference is noted between the 
portion treated with “floats” and that receiving applications of 
limestone. The floats, however, were applied after the manure had 
been plowed under. While no direct comparison can be made be- 
tween acid phosphate and ground raw rock in this experiment it will 
be seen that where the soluble phosphate was employed (in com- 
plete fertilizers) in addition to the floats the yields were consid- 
erably greater than where the floats were used in conjunction with 
potash and nitrogen carriers only. 
In Table LVII the average yields of each of the five crops of the 
rotation throughout the entire period of the experiment are given. 
These averages include six crops each of corn, oats, wheat, and clover - 
and three crops of timothy grown in four years and averaged as 
four crops. 
TasBLeE LVII.—Average yields of crops, on plots treated with lime and floats, 
five-year rotation, Strongville. 
Plots and treatment and average yield per acre. 
Plots Nos. Plots Nos. Plots Nos. 
Plots Nos. | 3, 5, 9, nitro- 17 to 33, 11 to 36, 
Crop. Unfertilized. 18, 20, 30, gen or potas- | complete fer- | complete fer- 
yard manure. sium; no tilizer, low tilizer, high 
phosphorus. nitrogen. nitrogen. 
| nem ft 
Come: Pe he bushels. .| 24.92 | 28.53 | 35.96 | 35.53 | 26.61 | 32.03 | 38.44 | 36.78 | 37.40 | 37.81 
Oats eee ee bushels...) 33.41 | 40.71 | 40.74 | 48.04 | 36.10 | 44.37 | 45.90 | 52.13 | 44.27] 51.21 
Witeatit lek mec pushels..| 8.38 | 10.06 | 18.33 | 17.69] 8.82] 10.43 | 19.79 | 17.70 | 20.43 | 18.48 
Glover... at eee. pounds. .| 2,383 | 3,650 | 3,945 | 4,653 | 2,587 | 3,921 | 3,504 | 3,974 | 3,630 | 4,217 
Mimothy= ase aoe pounds. .| 1,809 | 2,890 | 2,294 | 3,090 | 1,818 | 2,539 | 2,262 | 3,126 | 2,356 | 3,096 
This table shows in a more condensed form what is shown in de- 
tail in Table LVI namely, that floats when applied liberally are 
effective on a soil of low phosphate content and that probably their 
chief function is the furnishing of phosphoric acid. 
In this particular experiment the raw rock phosphate apparently 
became increasingly available after the soil had been plowed and 
cultivated for a number of years, and the finely divided rock thus 
more uniformly and thoroughly distributed. 
The writers feel that the work of the Ohio Experiment Station 
shows pretty conclusively that even medium applications of ground 
raw rock phosphate have produced decided increases in the yield 
