aa 
EXPERIMENTAL WORK WITH BAW ROCK PHOSPHATE. 3 
the Ashley phosphates in leu of bones as far back as 1860. A number 
of years later (1889), when the Florida hard rock phosphate fields 
were discovered, a considerable tonnage of soft phosphate (consist- 
ing chiefly of aluminum phosphate). which is found associated with 
the hard rock, was used locally by the farmers, and in a good many 
instances with reported success. 
Some early adverse reports on the agricultural value of raw rock 
phosphate, coupled with the rapid establishing of plants for the 
manufacture of the more soluble and undoubtedly more quickly act- 
ing superphosphate, led to the practical cessation of use of this raw 
material in the South, and, while spasmodic efforts have been made 
to revive its use, it is generally believed that the more soluble phos- 
phates are better adapted to most of the soils and crops of the South 
Atlantic States. 
The first recorded work with raw rock phosphate was published 
by the Pennsylvania Experiment Station in 1885.1 and consisted of 
two experiments (one field and one box experiment) begun in 1883. 
The box experiment was continued for two years only, but the fietd 
experiment was conducted through a period of thirteen years. 
The Louisiana station was the next to report the results of ex- 
periments with this material, publishing in 1886? the yields of corn 
and oats obtained in several tests conducted for periods of one to two 
years. 
Some years later this same station undertook a number of long- 
time experiments with raw rock phosphate, the results of which 
are recorded and discussed elsewhere in this bulletin. 
Several other experiment stations (Florida, Connecticut, Georgia, 
and South Carolina) shortly afterward undertook some experiments 
with raw phosphates, and these have been followed by practically 
all the State stations east of the Mississippi River and a few of 
those west. The results obtained by the stations are discussed in 
detail further on. 
THEORETICAL CONSIDERATIONS. 
The fact that most deposits of amorphous phosphates are of or- 
ganic origin led many to believe that this material when ground 
and applied directly to the soil would give results approximating 
those obtained from the use of nitrogenous guanos or ground bone. 
A brief consideration of the manner in which deposits of rock 
phosphate are usually formed will show that it can not ordinarily be 
expected to yield its phosphoric acid as rapidly to the soil solution 
as the organic phosphates which have not undergone complete de- 
composition. 
1Pa. Agr. Expt. &ta., Ann. Rept. for 1884 (1885). 
2La. Agr. Expt. Sta., Buls. Nos. 3, 4, and 6 (1886). 
