~~ 
EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. AQ 
lower yields in nearly every case than those treated with manure 
alone. In three out of six cases ground rock alone exceeded a mix- 
ture of ground rock and manure. 
In this publication the authors state that these experiments were 
to be continued, but no further results of the tests have yet been 
published. 
In 1914 the Kentucky station, in a bulletin on “Alfalfa and Sweet 
Clover,”* gave the results obtained in a single season with these 
crops when treated with raw rock and acid phosphate, but since the 
work was not continued beyond one year and the data given are very 
limited the figures are not repeated. 
In 1915 and 1916 Roberts? published the results of an experiment 
conducted at Burnside, Pulaski County, which had been running 
since 1908. The field used lies on a hillside of moderate slope. The 
soil consists of a badly worn limestone clay, very low in organic 
matter, which had produced poor crops for a long time; practically 
no manure had been returned to it for many years. In 1908, less 
than 34 bushels of wheat per acre were produced on this field, 
although it had received 200 pounds per-acre of an 8-2-2 fertilizer. 
In the summer of 1908, after the wheat was harvested, the field 
was laid out in six plots of one-fourth acre each, and the following 
fertilizers were applied on the unbroken ground and plowed under: 
Phosphate rock, 2,000 pounds per acre; acid phosphate, 800 pounds 
per acre; muriate of potash, 400 pounds per acre. Cowpeas were 
then sown and later turned under. The plots were then planted to 
rye and vetch, and while the latter crop failed the rye made a good 
growth. In the case of both cowpeas and rye the acid phosphate 
plots gave greater yields. 
No more fertilizer was apphed until 1911, then a heght dressing 
of manure was added to each plot, equivalent to what the corn and 
oats crops of each plot would make. In 1912 another such applica- 
tion of manure was added to the plots in addition to the same ap- 
plications of fertilizer materials as in 1908. In the spring of 1914 
a uniform dressing of nitrate of soda was applied to all plots because 
wheat was so backward. Manure was again added at the same rate 
as before in 1915, and potash and phosphates at one-fourth the rate 
previously employed. 
The results of seven years’ work are given in detail in Table XXYV. 
1Ky. Agr. Expt. Sta., Bul. 178 (1914). 
2Ky. Agr. Expt. Sta., Bul. No. 191 (1915); Bul. No. 199 (1916). 
56841°—Bull. 699—18—_4 
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