96 



BULLETIN 699, U. S. DEPAETMENT OF AGEICULTTJEE. 



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 com, oats, wheat, and clover 

 and three crops of timothy grown in four years and averaged as 

 four crops. 



Tabls LVIL — Average yields of crops, on plots treated vnth lime and floats, 

 , ^ five-year rotation, Strongville. 





•op. 



Plots and treatment and average yield per acre. 



(k 



Unfertilized. 



Plots Nos. 



18, 20, 30, 



yard manure. 



Plots Nos. 

 3, 5, 9, nitro- 

 gen or potas- 

 sium; no 

 phosphorus. 



Plots Nos. 

 17 to 3.3, 

 complete fer- 

 tilizer, low- 

 nitrogen. 



Plots Nos. 



11 to 36, 



complete fer- 



tihzer, high 



nitrogen. 





Lime. 



Floats. 



Lime. 



Floats. 



Lime. 



Floats. 



Lime. 



Floats. 



Lime. 



Floats. 



Com 



Oats 



Wheat 



Clover 



Timothy 



bushels.. 



bushels.. 



bushels.. 



pounds.. 



pounds.. 



24.92 

 33.41 

 8.38 

 2,383 

 1,809 



28.53 

 40.71 

 10.06 

 3,650 

 2,890 



35.96 

 40.74 

 18.33 

 3,945 

 2,294 



35.53 

 48.04 

 17.69 

 4,653 

 3,090 



26.61 

 36.10 

 8.82 

 2,587 

 1,818 



32.03 

 44.37 

 10.43 

 3,921 

 2,539 



38.44 

 45.90 

 19.79 

 3,504 

 2,262 



36.78 

 52.13 

 17.70 

 3,974 

 3,126 



37.40 

 44.27 

 20.43 

 3,630 

 2,356 



37.81 

 51.21 

 18.48 

 4,217 

 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 



