Erodibility of Sandy Loam Aggregates in Relation to Their Size and Initial Moisture Content Under Different Land Uses in Semi-Arid Tropics of India

Abstract

Soil erodibility, an index of ease of detachment of soil aggregates due to beating action of falling raindrops, is generally characterized through soil physical properties-based indices, which may not be applicable universally. The water stability of aggregates as determined by simple shaking under water though a more reliable index, does not simulate the actual field situation. The present study was conducted to determine the erodibility of natural, undisturbed soil aggregates from agricultural, forest, pasture, and eroded land uses from Punjab, India, in relation to their size and moisture status, using simulated raindrops in the laboratory. The mean EISRT (single raindrop technique-based erodibility index) was least under pastures followed by forest, agricultural, and eroded soils. The erodibility of aggregates increased significantly with an increase in aggregate size. Increasing the initial moisture content of aggregates resulted in increased erodibility with air-dry aggregates being the least erodible and the saturated ones the most. The effect of land use on soil erodibility was more pronounced when the aggregates were air-dried. The bigger (4.5 mm) raindrops did not differentiate the erodibility of aggregates from different land uses due to higher kinetic energy of the individual raindrops. The total number of raindrops used to completely disrupt an aggregate decreased with an increase in the size of raindrops. At saturation, even the aggregates from the pasture lands became unstable and their erodibility increased. Thus, the erodibility of bigger (> 10 mm) saturated aggregates was higher than the smaller saturated aggregates.