Methodological aspects of the quantification of dispersible clay and its relationship with soil properties along a catena under no-till management

Continuous no-till management of sloping cultivated areas can promote soil property transformations, causing changes in aggregation and dispersion. The objective of this work was (i) to quantify the readily and mechanically dispersible clays using different methods and (ii) to examine their relationships with soil properties along a catena under no-till management. For this study, the catena was divided into three distinct parts: crest, upper-slope and mid-slope positions. Undisturbed soil cores were sampled at each slope position to determine the following soil properties: organic carbon, Ca2+, Mg2+, K+, Al3+, P, pH, cation exchange capacity and total clay content. Additionally, the levels of readily dispersible clay were measured using turbidimeter and hydrometer methods, whereas mechanically dispersible clay was quantified using the turbidimeter method. We observed high influence of total clay content and organic carbon on soil flocculation; P, Mg2+ and cation exchange capacity were positively related to clay dispersion. Soil management and water transport downslope are probably influencing changes in soil properties and determining the distribution of dispersible clay contents along the catena. No relationships were observed between readily dispersible clay measured using turbidimeter and hydrometer in terms of quantity. Hydrometer and turbidimeter measurements can deliver significantly different results regarding dispersible clay quantification, potentially leading to misinterpretations concerning the amount of clay dispersed in water.