. Soils, their properties and management . ikely to occur in distinguishing betweenthe various finer grades of soil; for this reason morenearly exact methods are necessary at times, especiallyin checking soil survey work or in carrying out investiga-tions in which absolute accuracy is required. As a mechanical analysis of a soil is really a percentageexpression of texture, it presents an exact method forclass determination. For detailed work somewhat com-plicated tables ^ have been arranged; but the followingdiagram (Fig. 16), devised by Whitney,^ presents a simplemethod for the identification
. Soils, their properties and management . ikely to occur in distinguishing betweenthe various finer grades of soil; for this reason morenearly exact methods are necessary at times, especiallyin checking soil survey work or in carrying out investiga-tions in which absolute accuracy is required. As a mechanical analysis of a soil is really a percentageexpression of texture, it presents an exact method forclass determination. For detailed work somewhat com-plicated tables ^ have been arranged; but the followingdiagram (Fig. 16), devised by Whitney,^ presents a simplemethod for the identification of a soil from a mechanicalanalysis. The convenience of this triangular representa-tion may be tested by the use of the average analyses,already presented on a previous page. >Bur. of Soils, Soil Survey Field Book, p. 17, U. S. D. A.,Bur. Soils. 1906. Also, Bur. Soils, Bui. 78, p. 12. 1911. - Whitney, M. The Use of Soils East of the Great PlainsRegion. U. S. D. A., Bur. Soils, Bui. 78, p. 13. 1911. 100 SOILS: PROPERTIES AND MANAGEMENT. lO so JO ■aO so 60 70 80 yo l0O9(> Fig. 16. — Diagram for the determination of soil class from a mechani-cal analysis. 79. The significance of texture and class. — Soiltexture and class are the basis for all soil consideration,whether regarding some specific property or a generalcondition such as crop adaptation. No matter what thephase of soil study may be, texture and class are sureto have some important influence and nnist be includedin the investigation. From observations in practice,certain crops have been found to be adapted to certainkinds, of soil — as clay loam for wheat, silt loam forcorn, loam or sandy loam for potatoes, clay or clay loamfor timothy, and so on. Two authors ^ have determinedthe mechanical qualities of soils well adapted to certaincrops. An average of their analyses is given below: — » Hall, A. D., and Russell, E. J. Soil Surveys and SoilAnalyses. Jour. Agr. Science, Vol. IV, Part 2, p. 207. 1911. THE S
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