The effect of aggregate size on the infiltration behaviour of a slaking soil and its relevance to ponded irrigation

Abstract

The depth and degree to which columns of aggregates of different sizes of a structurally unstable red-brown earth surface soil slaked when water was ponded on the surface were studied. The slaking affected the subsequent infiltration into the soil. Wetting front advance and cumulative infiltration data indicated that the depth of the zone of slaking increased as the aggregate size increased. However, the effectiveness of the slaked layer in reducing the infiltration rate depended not only on the depth of slaking, but also on the extent to which the different aggregates had slaked into microaggregates and to what extent the microaggregates filled the interaggregate pores, if any. Examination of vertical sections of the slaked surface region using an optical microscope provided independent confirmation of the phenomenon of slaking in the various aggregate sizes.