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EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 89 
TABLE LIV.—Barnyard manure on erops grown in three-year rotation, etc.——Con. 
y 
Average annual increase obtained by comparison 
with average of all check plots. 
Plot 
fae Treatment. Corn, 18 crops. Wheat, 18 crops. | (0. 
Gane hay, 15 
Grain. Stover. Grain. Straw. LORS: 
= Bushels. | Pounds. | Bushels. | Pounds. | Pounds. 
al Vardumaniunerangdunloats asses see eee e 27. 54 1,312 13. 06 1, 242 1,718 
supovallamanureland floatsess sss = sss seek ee 30. 88 1, 525 14. 58 1, 437 2,138 
5 | Yard manure and acid phosphate...._.....-- 27. 83 1, 220 14. 69 1,475 1,621 
6 | Stall manure and acid phosphate............. 31.18 1, 426 15.18 1,599 2, 214 
Sil evandsmanureandikaimitese «55020 sees 20. 81 1,080 9. 64 991 910 
Oiescallimaninevandskainite 2s. s2ee see eee ae | oe 25. 68 1,323 11; 25 1, 259 1,601 
7a YVArdamManune ang: @ypSumMee == - 52s sa 24. 76 1, 248 12. 51 1, 280 1,278 
13) s5tallmanune and gypsum=2222- 22/2928 12. - 251/52 1,346 12. 43 1, 263 1,272 
PSR VanGamanturesumMErealed sy... 22-2. 2s eee 16. 99 769 6. 40 864 700 
16yStallamannreyfumbreated 2s s5 eee ce 4a See 23. 51 1,119 10.78 1,062 1,363 
See Chemicalotenuilizen aw sens sa) see ene oe eae 12. 24 548 3. 88 392 585 
IQ) ooee LO eee eae ta a RCT er ead Bes RET 10. 58 359 3. 73 471 722 
Fy eee pen pnt meee a ee 
A study of Table LIIT 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 
either 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, ete.” The latter writer also points out that several of the check 
plots in this experiment are apparently abnormal, and Thorne’s 
system of comparison is unfavorable if not unfair to the raw rock 
plots. 
1 Soil Fertility and Permanent Agriculture, p. 250. 
Ea ee SS eee eee eee ee 
