44 BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 
but none of these were conducted for a period of more than four 
years, so the results are not considered in detail. 
All the other experiments with raw rock phosphate conducted by 
the Indiana station are described and discussed by Wiancko and 
Conner’ in a recent bulletin entitled “Acid Phosphate versus Raw _ 
Rock Phosphate as Fertilizer.” 
Two of these experiments, one at Littles, in Pike County, and 
the other at Scottsburg, Scott County, were begun at the same time 
(1905), and are similar in every respect. There are three series of 
plots of one-twentieth acre each, and a three-year rotation of corn, 
wheat, and clover has been practiced, so that each crop could be 
grown on one series every year. “ When the clover failed cowpeas or 
soy beans were substituted. The land was plowed once in three years 
for corn, except when clover failed, when it was also plowed for 
soy beans or cowpeas. The wheat was drilled on disked corn stubble 
and the clover seeded on the wheat in the spring.” The various fer- 
tilizers were all applied to the wheat in the first round of the rotation, ~ 
the treatment being as follows: Manure at the rate of 10 tons per 
acre, raw rock at the rate of 1 ton per acre, and acid phosphate drilled 
with the wheat at the rate of 150 pounds per acre. After the first 
rotation manure was again applied at the same rate on every corn 
crop and acid phosphate on every wheat crop. A second ton of 
raw rock phosphate was applied for corn and cowpeas in 1911 and 
1912. Both fields were limed in 1911 at the rate of 2 tons of finely 
ground limestone per acre. While there were three check plots in 
each of the three series, the various fertilizer materials were repre- 
sented by only one plot in each series. . 
The field at Littles is nearly level with a slight slope running 
lengthwise of the plots. The soil is described as a yellowish brown 
silt loam of medium fertility. The phosphoric acid content as de- 
termined by analysis is 0.13 per cent. 
The Scottsburg field is alshost level on one series, but rises grad- 
ually through the two other series of plots. The soil is Volusia silt 
loam and is considered of low fertility. The total phosphoric acid 
content as determined by analysis is less than 0.1 per cent. The 
average yields of the three crops on both fields during the 10 years 
of the experiment are given in Tables XX and X XI. 
1Ind. Agr. Expt. Sta., Bull. No. 187, vol. 18 pp. 1055-1082 (1916). 
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