EXPERIMENTAL WOEK WITH RAW EOCK PHOSPHATE. 49 



lower yields in nearly every case than those treated Avith 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 3^ 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 cow^peas and rye the acid phosphate 

 plots gave greater yields. 



No more fertilizer was applied until 1911, then a light 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 XXV. 



iKy. Agr. Expt. Sta., Bui. 178 (1914). 



2Ky. Agr. Expt. Sta., Bui. No. 191 (1915) ; Bui. No. 199 (1916). 



56841°— Bull. 699—18 i 



