. Soils and fertilizers . , lines are drawn from the pointmarked 40 percent silt and 15 percent clay, the lines beingparallel to the sides of the right angle formed at 0. It willbe found that these lines intersect in the space markedloam, which is the class to which the soil belongs. If a soilhas 20 percent silt and 10 percent clay, the intersection of thelines drawn from these points falls in the space marked sandyloam, and the soil belongs to that class. TEXTURE AND STRUCTURE OF SOILS 35 cunr 34. Some properties of the separates. — In addition todifferences in their size, there are other dis
. Soils and fertilizers . , lines are drawn from the pointmarked 40 percent silt and 15 percent clay, the lines beingparallel to the sides of the right angle formed at 0. It willbe found that these lines intersect in the space markedloam, which is the class to which the soil belongs. If a soilhas 20 percent silt and 10 percent clay, the intersection of thelines drawn from these points falls in the space marked sandyloam, and the soil belongs to that class. TEXTURE AND STRUCTURE OF SOILS 35 cunr 34. Some properties of the separates. — In addition todifferences in their size, there are other distinctions that aremore or less characteristic of these separates. A mechanicalanalysis, therefore, tells us something about several of theproperties of a particles, byreason of their mi-nute size, tend tomake a soil plasticand may cause it tobecome hard, com-pact and cloddywhen dry. Siltdoes this to a muchless degree. Theextent to which asoil exhibits theseproperties dependson its content ofclay or silt. Soils. Fig. 4. — Plan by which the soil class may beascertained from a mechanical analysis. much clay or silt must not be plowed when wet or they will clay and silt serve to increase the water-holding powerof a soil, and clay especially increases the difficulty of tillage. The sand separates have the opposite properties ofclay, and in the order of their greater size of soils are more easily worked, are not likely to puddleor to form clods, and. do not hold a large amount of water,but on the contrary have a tendency to become dry. Sandysoils are termed light soils because they are easy to till;clay soils are called heavy because they make a heavydraft on the plow. The absolute specific gravity, or weight of the particles ascompared with the weight of the volume of water which 36 SOILS AND FERTILIZERS these particles would displace if they were immersed in it,does not necessarily correspond to these terms. Particles ofgreater and less spe
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