Towards a new approch for assessing the hazardous effects of soil salinity and sodicity

Abstract

This study deals mainly with the assessment of salt-affected soils and the role of the clay li•action in such assessment. Two natural soils, extremely differing in their texture, were se.lected from two locations in the south of Delta, Tlikh district i.e. Moshtohor (::58% clay) and Meet Kinana (:: 96% sand) to develop the soil models needed for the study. Soil samples of both locations were treated with NaCI + CaCh to obtain salinity grades corresponding to EC values of 2.75, 4, 8, 12, 16, 20 and 24 dSm-1 • Follo.wing to soil salinization, a sodication process was perfonned using NaOH solution to obtain seven levels of sodicity corresponding to ESP values of I 0, 15, 20, 25, 30, 40 and 50, through each of the abovementioned grades of soil salinity. Therefore the three c;Jicgories of salt-affected soils i.e. sodic and saline-sodic soils were represented through the prepared soil models. The role of the clay fraction on the hazardous effects due to salinity and/or sodicity was evaluated in soil models derived from the aforementioned soils; by mixing each model derived from one soil, in increasing ratios, with the corresponding model of the other soil i.e. of the same salinity and sodicity levels. Accordingly, eight different grades of soil texture having clay content values of 2.32% (SI), 7.77% (S2), 16.12% (S3), 24.46% (S4), 32.82% (S5), 41.47% (S6), 49.52% (S7) and 57.98% (S8) were obtained through each grade of salinity (7) or sodicity (7). Moreover, seventy samples representing the naturally salt-affected soils 111 E :,>ypt were collected from different locations, adjacent to the bitter lakes in the cast to the Delta and lakes of Manzala, Burullus, Edku and Mariut at Delta northem coasts. Both prepared soil models and naturally salt-affected soils were subjected to the routine analyses; EC, exchangeable cations and CEC as well as ESP and hydraulic conductivity (K).