Impact of clay content, salinity and sodicity on soil strength of some vertisols and an aridisol
2001
Mohamed, M.A. (Agricultural Research Corporation, Wad Medani (Sudan)) | Mustafa, M.A. (University of Khartoum, Shambat (Sudan). Faculty of Agriculture)
A study was undertaken to investigate the impact of clay content, ECe and SAR on the soil strength as indicated by modulus of rupture (MOR) of fifty-seven surface soil samples belonging to some vertisols' (Gezira) and Aridisol's (Al-Rawakeeb) series. Regression analysis of the data obtained using natrural soil samples showed significant increase in MOR with decrease in clay content (R2=0.263) and increase in ECe (R2=0.210), but they rendered very low accountability of the variation of MOR. No correlation was found between MOR and SAR or ESP. However, samples equilibrated with NaCl-CaCl2 salt solutions exhibited significant increase in MOR with increase in SAR and decrease in salt concentration. The MOR versus SAR relationships at constant salt concentration (C) values significantly fitted polynomial and linear trend lines, with conefficients of determination ranging between 87.4 to 99.9%. Both models gave a base line MOR value (intercept) that can be used as an index for identifying a hard-setting soil. However, the linear model was preferred because unlike the other one, it gives a sodium sensitivity value (slope) independent of SAR. According to the criterion set previously by Aylmore and sills (1982), the Aridisol is a hard setting soil, and although the Gezira Vertisols gave relatively high base line MOR value, the did not meet the criterion even under an ionic environment most conducive to dispersion
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