108 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
A more valuable experiment with raw rock phosphate is that re- 
ported by Keitt* in 1914. While the results of four years’ work in 
the growing of corn and cotton on plots treated with various phos- 
phates alone, and in combination with other fertilizer materials have 
been reported, this work is said to be only preliminary and is there- 
t 
fore not discussed here. 
None of the experiments of the South Carolina station have been 
continued long enough to warrant discussion and therefore no con- 
clusions may be drawn concerning the value of raw rock phosphate 
as a fertilizer. 
“TENNESSEE. 
The Tennessee station has published the results of 10? field ex- 
periments with raw rock phosphate. Seven of these experiments 
cover periods of only one to two years. | 
The average results obtained in three experiments covering periods 
of from three to four years and conducted by, or under the direction 
of the State station, were published by Mooers? in 1912. A rotation 
of cowpeas and wheat was practiced in these experiments and four 
different types of phosphate fertilizers were tested both on limed and 
unlimed plots. 
The beneficial effect of thine on these three forms was quite 
~ marked except in the case of the raw rock phosphate and basic slag 
_ plots. The latter material appears to have been the most effective of 
all the phosphates, aye in part no doubt to the free lime which it 
contained. 
If the average yields of all three forms are considered, the raw rock ~ 
plots (unlimed) compare very favorably with the acid phosphate 
(unlimed) plots, but where lime was applied the average yields 
were considerably more favorable to acid phosphate. 
If, however, the average yields obtained on the station farm only 
are considered (the experiment at this place having been conducted 
the longest) the raw rock phosphate plots compare favorably with 
those receiving acid phosphate and bone both on limed and unlimed 
land. 
These three experiments have not been running long enough to 
give conclusive evidence on the relative values of the four forms of 
phosphoric acid used and therefore are not repeated in detail, but the © 
indications are that applications of raw rock phosphate were effec- 
tive in increasing the yield of various crops. 
1S. Cc. Agr. Expt. Sta., Bul. No. 178 (1914). 
2Tenn. Agr. Expt. Sta., Ann. Rept. 1885-1886, pp. 100—112 (1886); Bul. No. 2, vol. 
138, pp. 11-14 (1900) ; Bul. No. 1, vol. 16, pp. 14-16 (1903) ; Bul. No. 86 (1909); Bul. 
No. 90 (1910) ; Bul. No. 92 (1911); Bul. No. 96 (1912). 
®Tenn. Agr. Expt. Sta., Bul. No. 96, pp. 15-24 (1912). 
