EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 89 



Table LIV. — Barnyard manure on crops grown in three-year rotation, etc. — Con. 



Plot 

 num- 

 ber, 



Treatment. 



Yard manure and floats 



StaJl manure and floats 



Yard manure and acid phosphate 

 Stall manure and acid phosphate . 



Yard manure and kainit 



Stall manure and tainit 



Yard manure and gypsum 



Stall manure and g5"psum 



Yard manure, untreated 



Stall manure, untreated , 



Chemical lertiUzer i 



do* 



Average annual increase obtained by comparison 

 with average of all check plots. 



Com, 18 crops. 



Grain. Stover. 



27.54 

 30.88 

 27.83 

 31. IS 

 20.81 

 25. 68 

 24.76 

 25. 52 

 16.99 

 23. 51 

 12.24 

 10.58 



Pounds. 



1,312 



1,525 



1,220 



1,426 



1,080 



1,323 



1,248 



1,346 



769 



1,119 



548 



359 



Wheat, 18 crops. 



Grain. 



Bushels. 

 13.06 

 14.58 

 14.69 

 15.18 



9.64 

 11.25 

 12.51 

 12.43 



6.40 

 10.78 



3.88 



3.73 



Straw. 



Pounds. 

 1,242 

 1,437 

 1,475 

 1,599 



991 

 1,259 

 1,280 

 1,263 



864 

 1,062 



392 



471 



Clover 

 hay, 15 

 crops. 



Pounds. 

 1,718 

 2, 138 

 1,621 

 2,214 



910 

 1,601 

 1,278 

 1,272 



700 

 1,363 



585 



722 



1 Acid phosphate, : 

 ' Acid phosphate. 



I pounds; muriate of potash, 80 pounds; nitrate of soda, 160 pounds, 

 t pounds; muriate of potash, 10 pounds; tankage (7-30), 100 pounds. 



A study of Table LIII will show that applications of stall manure 

 produced greater yields than yard manure, and that the mixing of 

 floats with the stall manure rendered them considerably more effective 

 than where they were mixed with yard manure. 



Phosphates proved more desirable as reenforcers of manure than 

 cither kainit or gypsum. Where the two forms, raw rock and acid 

 phosphate, were thus used at the rate of 320 pounds per acre every 

 three years, the plots treated with the latter gave slightly greater 

 yields. Moreover, in spite of the fact that a greater quantity of 

 phosphoric acid had actually been added to the plots in the form of 

 raw rock phosphate, and the conditions were favorable for render- 

 ing this accumulated phosphoric acid available, the acid phosphate 

 treatments appeared to be slightly more effective even after 17 years. 



On the other hand, Thorne in comparing the various fertilizer 

 treatments with the check plots assumes that any change in fer- 

 tility of the soil of the various plots in the experiment field is 

 gradual and, therefore, the treated plot under consideration should 

 be compared with the nearest check plots rather than with the 

 average of all the checks. 



Hopkins^ takes issue with Thorne on this point, saying "that 

 the change in the direction of such a curve is just as likely to occur 

 on any other plot as on the plots that happen to be numbered 1, 3, 4, 

 7, etc." The latter writer also points out that several of the check 

 plots in this experiment are apparently abnormal, and Thome's 

 system of comparison is unfavorable if not unfair to the raw rock 

 plots. 



1 Soil Fertility and Permanent Agricnlture, p. 250. 



