Laserfiche WebLink
U.S. LEPARTMENT OF AGRICULTURE PACE 2 OF 2 <br />NATURAL RESOURCES CONSERVATION SERVICE OB/17/00 <br />CHEMICAL PROPERTIES OF THE SOIL6 <br />Endnote -- CHEMICAL PROPERTIES OF THE SOILS <br />This report shows ea tima[ee of some characterise ica and features that affect soil behavior. <br />TRese estimates are given for the major layers of each soil in the survey area. The estimates <br />are based on field ebserva[ions and on cent data for these and similar soils. <br />CLAY ae a eo it asps rate consists of mineral soil particl ea that are less than 0.002 <br />millimeter in diameter. In this report, [he estimated clay content of each major soil layer <br />ie given as a percentage, by weight, of the soil material chat is less than 2 millimeters in <br />diameter. The amount and kind of clay greatly affect the fertility and phya ical condition of <br />[he sort. They determine the ability of the soil to adsorb cations and [o retain moisture. <br />They influence shrink-swell potential, permeability, and plasticity, the ease of soil <br />dispersion, and other soil properties. The amount and kind of clay in a soil also affect <br />tillage and earthmoving operations. <br />CATION E%CHANGE CAPACITY (CEC) ie the COtal amount Of Cat ions held in a 9oi1 in sllch <br />a way that they can be removed only by exchanging with another cation in the natural soil <br />solution. CEC ie a measure of the ability of a soil to retain cations, some of which are <br />plant nutrients. So ile with low CEC hold few cations and may require more frequent <br />applications of fertilizers than soils with high CEC. Soils with high CEC have the potential <br />to retain cations, thus reducing the possibility of pollution of ground water. <br />SOlu REACTION is a measure of acidity or alkalinity and is expressed as a range in pN <br />values. The range in pH of each major horizon is based on many Eield tests. For many soils, <br />values have been verified by laboratory analyses. Soil reaction is important in selecting <br />c ropy and other plants, Ln evaluating soil amentlmen is for fertility and stabilization, and <br />in determining Che risk Of corrosion. , <br />CALCIUM CARBONATE Se the percentage by weight of calcium carbonate in the fine-earth <br />material, leas Chan 2 millime tera in size. <br />GYPSUM is the percentage by weight of hydrated calcium sulfates 20 millimeters or <br />Smaller in size, in Che soil. <br />SALINITY is a measure of soluble salts in the soil at saturation. IC is expressed <br />ae [he electrical conductivity of the sacurat ion extract, in millimhos per centimeter <br />at 25 degrees C. esti ma ces are based on Eield and laboratory measurements at representative <br />Bites of nonirrigated soils. <br />The salinity of irrigated soils is affected by the quality of the irrigation water <br />antl by the frequency of water application. Hence, the salinity of soils in individual fields <br />can differ greatly from [he value given in the report. Salinity affects the suitability of <br />a sail for crop production, Che atabil icy of soil if used as construction material, and <br />[he potential of the soil to corrode metal and concrete. <br />SODIUM ADSOA PTI ON RATIO (SAN) express ee Che relative activity of sodium ions in <br />er 'mange reactions in the soil. SAR is a measure of Che amount of sodium relative to <br />c. um and magnesium in Che water extract Erom saturated soil paste. <br />