612 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



progrci^s of the soil survey and to render it easily accessible to farm- 

 ers, teachers, invest iira tors of soil problems, students of agricultural 

 economics, and investors in farm lands. They will ultimately serve 

 to })resent the first classified and detailed description of the available 

 soil resources of the Nation. 



• 



SOIL CHEMISTRY. 



Work has continued in determining the composition of important 

 soil types. The very large number of minerals found in rocks has 

 been found to be present in most soils, and the natural productivity of 

 a soil has been shown to be associated with mineral heterogeneity. 

 Careful chemical analyses have shown that practically all of the 

 mineral elements are usually present in a soil and that some of these 

 elements probably have an importance in plant production and soil 

 management not hitherto suspected. 



Sulphur is important for the growth of many species of plants, if 

 not of all. The quantity naturally j^resent in most soils is quite low, 

 and that it may have an importance in fertilizer practice hitherto not 

 appreciated seems quite probable. Vanadium is found in most soils 

 in amounts comparable with phosphorus. Manganese, important in 

 effecting oxidation processes in soils, has been found to be concen- 

 trated in surface soils. Silica has been shown to be higher in the 

 surface soil than in the subsoil, while iron, aluminum, and titanium 

 are uniformly higher in the subsoil. Lithium is present in all soils. 

 Rubidium and ciesium have not been found. The rare earths are 

 present in all cases, as are chromium, vanadium, zirconium, barium, 

 and strontium, in decided amounts. Radio-activity has been shown 

 not to be characteristic of either soil or subsoil particularly, but rather 

 it is associated with sulphates of barium, strontium, and possibly 

 other mineral salts. It has been show n that while certain fertilizers 

 which have recently come into the American market, such as ground 

 feldspar, ground phonolite, ground lava, etc., may occasionally pro- 

 duce a favorable result, there is no scientific basis for believing that 

 they would generally produce any special or lasting improvement in 

 the soil, and they can not be expected to replace the standard mix- 

 tures of mineral salts commonly found in high-grade commercial 

 fertilizers. 



Work has been continued in the investigation of the properties of 

 the soil solution and the alteration and decomposition of soil minerals. 



FERTILIZER INVESTIGATIONS. 



The fertilizer investigations have shown that the United States 

 contains ample raw materials for the production of all the standard 

 fertilizer materials that it now^ demands. The giant kelp groves on 

 the Pacific coast from the Mexican border to Cape Flattery have 

 been mapped and Avork is in progress, from which it will soon be 

 possible to estimate the value of this great resource. It is known 

 now hat it can produce several times the present needs of the country 

 in potash salts. The investigations of the desert basins of the United 

 States have been continued and the several basins of commercial 

 promise have been delimited. Potash salts of commercial value are 

 now known to exist in one — Searles Lake — and this bureau, the 



