Dispersive Behavior of Saline Sodic Soils under Arid Conditions

Abstract

This work aims to investigate the dispersive behaviour  of  saline sodic soil of lower Chellif soils and classify them after the measure of their clay dispersion indices,  mechanical and spontaneous dipersion. The laboratory investigation used thirty-two soils from the (0-20cm) of Hmadna in Lower Chellif Algeria. After characterisation of soil solution, we calculated Sodium Adsorption Ratio and Cations Ratio of soil Structural Stability.Water Dispersible Clay, Clay Dispersible Ration, and Clay Flocculation Index were explored. Correlation analysis were used. Spontaneous  and Mechanical Dispersion were measured and threshold lines relting SAR and CROSS to EC were derived for the two types of dispersion. They were used to indicate the dispersive behaviorThe studied soils show a variation of electrical conductivity from 0.95 to 7 dS/m. Sodium constitutes the most abundant soluble cation whereas potassium is the last one. SAR ranged from 3.84 to 12.77 and CROSS from 4.17 to 14.18. Water Dispersible Clay ranged from 0.34 % to 1.10 %, low averages but variable with a coefficient of variation  of 36.68%. Clay Dispersible Ratio presents a coefficient of variation of 37,42%.  The coefficient of variation of Clay Flocculation Index was about 0.44%.The Results show that Spontaneous Dispersion ranged from 0.08% to 0.45%, with a mean of 0.22%, Mechanical Dispersion ranged from 0.12% to 0.62%, with a mean of 0.34%.Mechanical Dispersion  and Water Dispersible Clay had a high significant positive correlation with EC, SAR, CROSS, K⁺, Mg ^2+, Na⁺ and a significant positive correlation with Ca²⁺. Spontaneous Dispersion showed a significant positive correlation with EC, SAR, CROSS, K⁺, Mg ^2+, Na⁺, significant positive correlation  with Ca²⁺. Correlation between clay dispersion indices indicated a high significant positive  correlation between Water Dispersible Clay and Mechanical Dispersion It was significant and positive  with Spontaneous Dispersion too The obtained shemes with the threshold lines  classified the saline sodic soils of lower Chellif as potentially dispersive. For an EC ≤ 8 dS/m and a SAR≤ 13, the studied soils start to loose their flocculation., indicating that for more disturbance of these soils on the field, they become more and more dispersive.Further researches need to be completed for a larger classes of salinity for a better characterisation of soil dispersion and dispersive behavior in lower Chellif especially with the important risk of salinisation and its implication on soil productivity of these soils which is observed in these recent years