Soil structural stability,as measured by water-stable aggregate rate(WSAR,the rate of >0.25 mm water-stable aggregate's weight in 1-5 mm dry aggregate's weight) and clay dispersion rate,and Atterberg limits(ALS) were assessed with relation to salinity,sodicity and organic matter on salt-affected soil samples taken from Jingdian Irrigation Area,Gansu.The obtained results showed that soluble salts were dominated by sodium ion.As a result,soils were sodic.With increase in salinity and sodicity,aggregate stability decreased and clay dispersion increased significantly,meanwhile,there was a declining trend in ALS.This clearly implied that salinization as well as increase in sodicity was one of the factors which are responsible for soil structural degradation.With increase in organic matter(OM),aggregate stability and ALS increased and clay dispersion decreased markedly,which showed that addition in organic matter to salt-affected soils can improve structural characteristics.On the effects of OM and ESP on aggregate stability,WSAR could be predicted according to the following equation:
WSAR=19.4+0.98OM-1.43ESP(R²=0.5741,n=67)
Aggregate stability,clay dispersion,liquid limit and plastic limit significantly correlated.This illustraced that liquid limit and plastic limit could be used to characterize the structure of salt-affected soils.