Laserfiche WebLink
Custom Soil Resource Report <br /> observations in the field or laboratory. Examples of soil chemical properties include <br /> pH, cation exchange capacity, calcium carbonate, gypsum, and electrical <br /> conductivity. <br /> Chemical Soil Properties (TZA - Chem) <br /> This table shows estimates of some chemical characteristics and features that <br /> affect soil behavior.These estimates are given for the layers of each soil in the <br /> survey area. The estimates are based on field observations and on test data for <br /> these and similar soils. <br /> Depth to the upper and lower boundaries of each layer is indicated. <br /> Cation-exchange capacity is the total amount of extractable cations that can be held <br /> by the soil, expressed in terms of milliequivalents per 100 grams of soil at neutrality <br /> (pH 7.0) or at some other stated pH value. Soils having a low cation-exchange <br /> capacity hold fewer cations and may require more frequent applications of fertilizer <br /> than soils having a high cation-exchange capacity. The ability to retain cations <br /> reduces the hazard of ground-water pollution. <br /> Effective cation-exchange capacity refers to the sum of extractable cations plus <br /> aluminum expressed in terms of milliequivalents per 100 grams of soil. It is <br /> determined for soils that have pH of less than 5.5. <br /> Soil reaction is a measure of acidity or alkalinity. It is important in selecting crops <br /> and other plants, in evaluating soil amendments for fertility and stabilization, and in <br /> determining the risk of corrosion. <br /> Calcium carbonate equivalent is the percent of carbonates, by weight, in the fraction <br /> of the soil less than 2 millimeters in size. The availability of plant nutrients is <br /> influenced by the amount of carbonates in the soil. <br /> Gypsum is expressed as a percent, by weight, of hydrated calcium sulfates in the <br /> fraction of the sod less than 20 millimeters in size. Gypsum is partially soluble in <br /> water. Soils that have a high content of gypsum may collapse if the gypsum is <br /> removed by percolating water. <br /> Salinity is a measure of soluble salts in the soil at saturation. It is expressed as the <br /> electrical conductivity of the saturation extract, in millimhos per centimeter at 25 <br /> degrees C. Estimates are based on field and laboratory measurements at <br /> representative sites of nonirrigated soils. The salinity of irrigated soils is affected by <br /> the quality of the irrigation water and by the frequency of water application. Hence, <br /> the salinity of soils in individual fields can differ greatly from the value given in the <br /> table. Salinity affects the suitability of a soil for crop production, the stability of soil if <br /> used as construction material, and the potential of the soil to corrode metal and <br /> concrete. <br /> Sodium adsorption ratio (SAR) is a measure of the amount of sodium (Na) relative <br /> to calcium (Ca) and magnesium (Mg) in the water extract from saturated soil paste. <br /> It is the ratio of the Na concentration divided by the square root of one-half of the <br /> Ca+ Mg concentration. Soils that have SAR values of 13 or more may be <br /> characterized by an increased dispersion of organic matter and clay particles, <br /> reduced saturated hydraulic conductivity and aeration, and a general degradation of <br /> soil structure. <br /> 24 079 <br />