INFLUENCE OF MAGNESIUM AND OF EASILY WEATHERED MINERALS ON HYDRAULIC CONDUCTIVITY CHANGES IN A SODIC SOIL

Exchangeable Mg appears to have no specific effect on soil hydraulic conductivity of A and C horizons of a sodic sandy loam soil (montmorillonite and kaolinite clay minerals) leached with solutions which cause clay swelling to be the dominant mechanism reducing conductivity (SAR < 20, electrolyte concentration 10 meq per litre). There is some evidence of a specific effect when these soils are subsequently leached with water which causes clay dispersion to become important. Fresh loess in the A horizon dissolves in percolating rainwater, causing difficulties in the replication of experiments. It seems to give a small degree of ‘self protection’ to soil structure, a property likely to be operating in other soils affected by recent loess deposits. Copyright © 1979, Wiley Blackwell. All rights reserved