Effect of soil organic matter, electrical conductivity and sodium adsorption ratio on tensile strength of aggregates

The properties of soils affected by salinity and processes involving degrad ation of soil structure have been partly recognized. However, the effects o f saline and sodic conditions on mechanical and physical properties of soil s have been studied to a lesser extent. In this research, the effects of el ectrical conductivity (EC) and sodium adsorption ratio (SAR) on soils posse ssing various amounts of organic matter were assessed under laboratory cond itions. The soils contained a uniform clay type, predominantly Illite. The major difference of the soils was their amount of organic matter content. T he treatments consisted of solutions with definite EC and SAR (two levels o f EC: 0.5 and 4 dS/m and three levels of SAR: 0, 5 and 15). The amount of t ensile strength was dependent on organic matter, EC, and SAR in a way that with the increase of SAR, the tensile strength decreased. In similar SAR, t reatments with higher EC exhibited greater tensile strength. Also, the soil s with higher organic matter showed greater tensile strength. The analysis of variance showed the significant difference (at 1%) between the mean of p arameters analyzed (soil type, sampling depth, EC, and SAR). The order of a verages of tensile strength were: permanent pasture (Agropyron elengatum)<i ntensive cultivation/permanent pasture (Festuca arusdinaceae)<virgin soil. The differences were also significant for the SAR factor. The order of aver ages were: SAR=15<SAR=5<SAR=0. (C) 2000 Elsevier Science B.V. All rights re served.