Abstract
Soil structural stability affects the profitability and sustainability of agricultural systems. Different-sized structural units have different stability mechanisms and respond differently to such external factors as rain, wind, irrigation and management. A comprehensive analysis of the soils structural stability requires its characterization at the macroand micro-aggregate scales. We determined the aggregate stability of 36 soils at the macro-aggregate scale using wetsieving methods and of 20 soils at the micro-aggregate scale using laser-ray diffraction techniques. All the tests gave consistent estimates of aggregate stability. Most soils were homogeneous and quite stable at the macro-aggregate level as determined by the "water stable aggregate" parameter, but differed significantly among them and were quite unstable at the micro-aggregate level as determined by the "mean weight diameter of micro-aggregates" parameter. Slaking induced by the fast wetting of aggregates was the main destabilizing mechanism in these soils (88% of the soils had slaking stability index values < 0.5), whereas most soils were quite tolerant to the mechanical shaking of aggregates (89% of the soils had stirring stability index values > 0.5). The combination of the macro- and micro-aggregate stability tests is a consistent way for describing the structural stability of the studied soils.
Highlights
Soil aggregate stability, defined as the ability of the aggregates to remain intact when subject to a given stress, is an important soil property that affects the movement and storage of water, aeration, erosion, biological activity and the growth of crops
Macro-aggregate stability may be quantified by means of the parameter «water stable aggregates» (WSA)
Macro-aggregate stability may be quantified by means of the parameter «mean weight diameter» (MWD) of the aggregates remaining stable after their exposure to three treatments plus a subsequent wet sieving in ethanol (Le Bissonnais, 1988)
Summary
Soil aggregate stability, defined as the ability of the aggregates to remain intact when subject to a given stress, is an important soil property that affects the movement and storage of water, aeration, erosion, biological activity and the growth of crops. Macro-aggregate stability may be quantified by means of the parameter «mean weight diameter» (MWD) of the aggregates remaining stable after their exposure to three treatments (fast wetting, slow wetting and stirring after prewetting) plus a subsequent wet sieving in ethanol (Le Bissonnais, 1988). This method, later modified by Amézketa et al (1996), is more laborious and complex than the standard Kemper and Rosenau test, but characterizes better some of the basic mechanisms of aggregate breakdown.
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