154 SOILS AND AGRICULTURAL CONDITIONS 



Sandy Loam, Bahama Eed Loam, Bahama Marl, Brackish Swamp, and Ba- 

 hama White Marl. The extent and locations of six of these are shown on the 

 accompanying colored maps. (Plates XXVIII to XXXII.) 



The classification of the soil types is based mainly on differences in 

 physical properties, as texture and color, but the physiographic position; 

 characteristic natural vegetation, and agricultural value were also considered 

 as factors in making the classification. Each type is essentially the same on 

 all the islands where it is found, varying no more as between different islands 

 than in different areas on the same island. The system of classification and 

 nomenclature of soil types followed is that established and in use by the 

 Bureau of Soils of the IT. S. Department of Agriculture. 



Accompanying the description of each soil type are mechanical and 

 chemical analyses of typical samples. The mechanical analyses were made 

 according to the procedure of the Bureau of Soils, IT. S. Department of 

 Agriculture. In the chemical analyses the method of the Association of 

 Official Agricultural Chemists 1 was followed, only the more important plant- 

 food constituents being determined. This method consists essentially of a 

 digestion in hydrochloric acid of specific gravity 1.115 for ten hours at 100 C. 

 The analyses of the water soluble salts was made by the methods in use by the 

 Bureau of Soils.'" In some cases considerable amounts of chlorides and sul- 

 phates were found to be present, and in such cases these constituents are 

 stated as well as those which are generally held to be more important from the 

 point of view of fertilizer practices. Two of the samples were so rich in 



1 Bull. No. 46, Div. of Chem., U. S. Dept. of Agric. 



2 Briefly, the method is as follows: 100 grams of the soil sample is stirred or 

 shaken vigorously for three minutes with 500 cc. of distilled water and allowed to 

 stand twenty minutes for the coarser soil particles to subside. The supernatant 

 liquid, containing suspended clay and other solid matter, is decanted from the 

 residue of heavier soil particles and filtered by means of a Chamberland-Pasteur, 

 unglazed, porcelain filter fitted to the forced air device described by Briggs (Bull. 

 No. 19, p. 31, Bureau of Soils, U. S. Dept. of Agric., 1902). The principal plant-food 

 constituents in this aqueous extract are then determined colorimetrically, the 

 nitrates by developing the yellow color resulting from the addition of phenol-disul- 

 phonic acid, making the solution slightly alkaline with ammonia, and, then com- 

 paring with a standard solution of potassium nitrate similarly treated; the phos- 

 phoric acid by comparing the yellowish color produced by ammonium molybdate in 

 nitric acid solution with a standard solution similarly prepared; the potassium by 

 making the potassium platinic chloride, and then measuring the red color produced 

 by an excess of potassium iodide against a standard solution of potassium platinic 

 chloride similarly treated; the calcium by an adaptation of the well-known Clark 

 soap method, modified by Winkler, Warthe, and others. For further details, see 

 Appendix in Bulletin No. 22, Bureau of Soils, U. S. Dept. of Agric., 1903. 



