EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 3 



the Ashley phosphates in lieu 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,^ 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 field 

 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 com 

 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 Elver 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. 



»Pa. Agr. Expt. Sta., Ann. Kept, for 1884 (1885). 

 a La. Agr. Expt. Sta., Buls. Nos. 3, 4, and 6 ( 



