816 EXPEBIMENT STATION EECORD. [Vol. 37 



applied, that in tlie slags was only about a third as effectual as In the other 

 form. . . . 



" Data concerning the relative availability of the phosphorus in slags and 

 other phosphates were secured by four pot experiments with dwarf Essex rape 

 and one with Japanese millet. A field experiment with these two crops was 

 also conducted for two years. The later experiments, both in the pots and 

 field, were carried out according to directions furnished by the basic slag com- 

 mittee of the Association of Official Agricultural Chemists. The use in the pots 

 of a preceding crop of crimson clover as a green manure did not increase the 

 relative availability of the phosphorus in the insoluble phosphates, slag, and 

 raw rock phosphate, or floats, in comparison with that in the soluble sources. 

 In the pot experiments, although the slags compared very favorably with the 

 soluble sources, the floats were decidedly inferior; even in large applications 

 the latter material failed to supply the needs of the plants. From soil to 

 which no phosphorus was added the millet absorbed per pot more than twice as 

 much as the rape did. , . . Even when applied in the most available source 

 more than four-fifths of the phofe-phorus became inaccessible to the first crop 

 planted after its application. 



" In the field experiments with both millet and rape results were obtained 

 for the year in which the various .sources of phosphorus were applied as well 

 as the after-effects in the following year. The raw rock phosphate was much 

 less available than the other sources of phosphorus. . . . Basic phosphate 

 yielded somewhat less than the other slags, which compared favorably with the 

 soluble phosphates. 



" It would seem from the results of the experiments . . . that if water- 

 soluble phosphate is considered entirely available, then a laboratory method 

 for determining the availability of Thomas slag phosphate should include the 

 use of some solvent which would dissolve nearly all of the phosphorus." 



The rate of reversion of mixtures of superphosphate with basic slag and 

 rock phosphates, G. S. Koukkt.son (Jour. Soc. Chcm. Indus., S6 (1917), No. 12, 

 pp. 626-628). — Experiment.s with mixtures of equal parts of 2G per cent water- 

 soluble supenihosphate and 26 per cent citric-soluble basic slag led to the con- 

 clu.slon that " on the whole it can not be said that a superphosphate and basic 

 slag mixture has anything particular In Its favor. If the basis of the mixture 

 is one-half 26 per cent superpho.sphate and one-half basic slag. It Is clear that 

 If the slag contains 2 per cent of caustic lime practically all the water-soluble 

 phosphate in the mixture will revert in a few hours." 



Experiments with equal parts of 26 per cent superphosphate and Gafsa rock 

 phosphate showed that " the water-soluble phosphate in the mixture reverts to 

 a much less extent than in the slag and superphosphate mixture. Tlie rever- 

 sion is, comparatively speaking, so small that there would be no serious objec- 

 tion to farmers making and applying such a mixture. . . . There seems to be 

 no serious difficulty in the way of manufacturers making such a mixture (1 of 

 supei*phosphate to 1 of rock phosphate) and selling it with a guaranty of 

 water-soluble phosphate, total phosphate, and, If advisable, citric-soluble phos- 

 phate." 



Phosphate rock in 1916, R. W. Stone (U. S. Oeol. Survey, Min. Resources, U. 

 S., 1916, pt. 2, pp. 29-Jil). — This report states that "the quantity of phosphate 

 rock marketed in the United States in 1916 was 1,982.385 long tons, valued at 

 $5,896,993, an increase of 146,718 tons in quantity and of $483,544 in value over 

 the production of 1915. This increase was comparatively small but it indicates 

 an Impi-ovement in the Industry, and suggests that In spite of the curtailment 

 In the exports the production of former years may in time be approached. . . . 



