dal 
EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 43 
TABLE XIX.—Average yields of corn, wheat, legumes, and oats, Cutler field. 
Average yield per acre (1904-1915). 
Treatment. 
Corn, 4 Wheat, 3 | Legumes,1} Oats, 2 
crops. crops. crop. crops. 
: Bushels. Bushels. Tons. Bushels. 
Residues, limes bone, potash 2626 e5--2. 625s. - cess ce 34.9 25st 2. 74 27.1 
Residues Mines potas. - o/s Beco cca os since aaisie 38. 4 16.9 2a 31.6 
Hamerspotasht tery. F312 5.500. L REE A oe Se oo I 36.9 16.3 1. 80 25.5 
Residues, lime, acid phosphate, potash................. 36. 0 28. 7 2.52 28.8 
imme; acid phosphate, potash. -! 2.1... ..-2--2... 226s] 37.1 26. 6 2. 40 31.8 
Residues, lime, phosphate rock, potash ................ 42.2 25.8 2. 51 24. 6 
Lime, phosphate rock, potash... 2.2.2.2. .e eee ccc cece Sie 18.5 2. 06 29.3 
In almost every instance plots treated with ground raw rock 
phosphate gave noticeable increases in yield over the check plots, 
and at Odin and Mascoutah showed to better advantage than the 
acid phosphate plots. At Cutler the acid phosphate plots appeared 
to greater advantage. However, none of the phosphate treatments 
gave very large increases, and, as Hopkins says, “ These investiga- 
tions have shown that phosphorus is not the factor which first limits 
the crop yields on these southern Illinois soils, both limestone and 
organic matter being of greater initial importance.” Owing to the 
adverse climatic conditions during the latter part of the experiment 
it is impossible to tell whether or not any cumulative eifect can be 
attributed to the use of raw rock. | 
The data presented in the 12 field experiments with raw rock 
phosphate conducted by the Illinois station and considered here in 
detail point pretty strongly to the conclusion that this phosphate 
carrier increases crop yields very materially when applied liberally. — 
Since raw rock was compared with other phosphates in only 3 
of the 12 experiments, and on fields where phosphoric acid appar- 
ently was not the limiting factor, the work hardly appears to justify 
a comparison of the relative merits of the different phosphate 
carriers. | 
INDIANA. 
The first mention of the use of raw rock phosphate as a fertilizer 
made by the Indiana Experiment Station was in 1896, when phos- 
phatic marl containing from 10 to 12 per cent of phosphoric acid 
was tried on two series of wheat plots of one-twentieth acre each. 
The short duration of this experiment (one year), however, and the 
little data presented make the results relatively unimportant. 
Two experiments with raw rock phosphate were described by 
Goss? in 1907 and several others by Abbott and Conner ?* in 1912, 
1Ind. Agr. Expt. Sta., Bul. No. 61, p. 64 (1896). 
2Ind. Agr. Expt. Sta., Circular No. 10, pp. 9-11 (1907). 
3Ind. Agr. Expt. Sta., Bul. No. 155 (1912). 
