P. A. Yoder

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Full Issue

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Within recent years much has been done toward determining the agricultural significance of certain physical properties of the soil. The grade of fineness is the most important of these physical properties, in that it determines, to a large extent, other properties. The· mechanical analysis of soils has thus come to be considered of primary importance in soil investigations. Any improvements in the methods or apparatus for mechanical analysis will, therefore, doubtless be welcomed by agricultural investigators. Though this is a very recent line of work, still many devices have been introduced for the separation of soil on the basis of fineness into different grades. The sieving can be carried out practically only for the coarser grades of sand and gravel. The original beaker methods in several modifications, all depending upon unequally rapid settling through quiet water, and subsequent decantation, were improved on by Noebel, Schoene and others by introducing a rising current of water. Hilgard has improved this method further by introducing at the bottom of the elutriation tube, a churn to break up floccules. Both the beaker method and these elutriation methods are open to the objection that for the finer separations they are very time-consuming, and that for the finest separations which are desirable, they are entirely impracticable. These very finest grades, however, differ most remarkable from the coarser grades, and their separation and quantitative determination is, therefore, the most desirable part of the mechanical analysis.

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Soil Science Commons



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