. Principles of agricultural chemistry [microform] . iedby ascertaining the mechanical analysis of soils of known prop-erties, and also by investigating the properties of the variousgroups of particles separated in the analysis. In sands the coarser particles of the soil predominate. Suchsoils are open or porous, easy to cultivate, not very retentive ofmoisture, and warm up early in the spring. Coarse sands areleast retentive of moisture and most porous. Soils containingquantities of very fine sand are much more retentive of moisture. 84 PRINCIPLES OF AGRICULTURAL CHLMISTRY In heavy clay soils
. Principles of agricultural chemistry [microform] . iedby ascertaining the mechanical analysis of soils of known prop-erties, and also by investigating the properties of the variousgroups of particles separated in the analysis. In sands the coarser particles of the soil predominate. Suchsoils are open or porous, easy to cultivate, not very retentive ofmoisture, and warm up early in the spring. Coarse sands areleast retentive of moisture and most porous. Soils containingquantities of very fine sand are much more retentive of moisture. 84 PRINCIPLES OF AGRICULTURAL CHLMISTRY In heavy clay soils, the fine clay particles are present in largequantity. Such soils are very retentive of moisture, requiremuch labor in cultivation, are likely to be tough and sticky whennot ploughed at exactly the right time, are not easily penetrated UNITED STATES DEPARTMENT OF AGRICULTURE, DIVISION OH AGRItULTURAI- SOILS. THE TEXTURE OF A TVPJCAL TOBACCO LAND AT HATFIELD. MASSACHUSETTS. iTo. Xi73. Par Cent of Gravel. Sand. Silt, and In 20 (i. of Sul» DIAMETER OF THE GRAINS IN MILLIMETERS. Fig. 27.—Physical analysis of a soil sample. Bureau of Soils. by water, and do not warm up rapidly in the spring. Twenty percent, clay particles usually make a soil difficult to work. Soils with much silt and little or no clay, are likely to adhere PHYSICAI, COMPOSITION AND CI,ASSE;S OF 85 to the plow very tenaciously when too wet. They plough fairlywell when in right condition, but turn up in clods if ploughedwhen dry. Loams are intermediate between sands and clays, inphysical character and in properties, and in general are good soils. The coarse soil particles, therefore, tend to make the soil moreopen and porous and more easily tilled. The fine particles tendto make the soil more compact and less easily tilled. The finalresultant depends upon the relative quantities of the differentkinds of particles, as well as their chemical composition or theirproperties. The presence of a certai
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