Aggregate stability of some alluvial soils from Egypt.

Abstract

[134:116.46:141.621]The hypothesis that the Ca-Mg balance is the factor determining the structural stability of these soils was supported in the case of silty clay samples, where a positive correlation was found between the aggregate index and the Ca contents and Ca/Mg ratio, and a negative correlation with the Mg and Na percentage. With silty clay loam samples however a significant negative correlation was found between aggregate index and the Na content and percentage of 0.05-0.10 mm particles, and a positive correlation with the percentage of clay particles. In this case there was evidence that the presence of exchangeable Na aggravated the effect of Mg on aggregate stability. In both groups of samples the percentage of Na was correlated at P <0.05 with the Ca/Mg ratio, which made it impossible to ascribe the harmful effect on aggregate stability to an increase in Na or a decrease in Ca/Mg ratio. Multiple regression involving the most significant constituent variables accounted for <40% of the total variance of aggregate stability. It is therefore concluded that the variables included in the multiple regression cannot be the exclusive cause of the aggregate stability even though among the many factors affecting the structure of the soil these variables may well exert a strong influence. (Abstract retrieved from CAB Abstracts by CABI’s permission)