|Huang, Chi hua|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/2/2005
Publication Date: 3/29/2006
Citation: Mamedov, A., Huang, C., Levy, G.J. 2006. Antecedent moisture content and aging duration effects on seal formation and erosion in smectitic soils. Soil Science Society of America Journal.70:832-843. Interpretive Summary: Seal formation and erosion depends on soil properties and surface conditions. Antecedent moisture content (AMC) and aging duration (time from the previous rain event) are two factors affecting runoff and erosion. Nevertheless, results on AMC and aging effects are inconclusive. In this research we precisely controlled the AMC and aging duration for 4 soils: loam, sandy clay and 2 clay soils all having the same type of clay (smectite). After aging for a pre-selected period, the soil trays were exposed to 60 mm of rain. With no aging, runoff volume and soil loss increased with an increase in AMC. This is due to the enhanced aggregates breakdown. However runoff and soil loss decreased with the increase in aging duration. The smallest runoff volume and soil loss were obtained at the intermediate (2-4mm) AMC levels, generally between wilting point and field capacity. At this optimal AMC level, water-filled pores in the clay structure were active in the stabilization process and the development of cohesive bonds between and within particles during the aging period. This research clarifies the dispute on AMC and aging effects, and furthermore, indicates the sensitivity and intricacy of soil moisture condition in stabilizing soil aggregates. The impact of the research is an improved understanding in soil aggregation which can lead to a more accurate estimate of soil erodibility.
Technical Abstract: Soil susceptibility to seal formation and erosion depends on its inherent properties as well as on surface conditions. Our objective was to examine the effects of antecedent moisture content (AMC) and aging duration (i.e., 2 different surface conditions) on seal formation and erosion in 4 smectitc soils. Soil samples were packed in trays and wetted with different amounts of water (0, 1, 2, 3, 4, 6, 8, or 16 mm) with a mist type rain. The wetted samples were put in plastic bags and allowed to age for 0.01, 1, 3, or 7 days at 25oC. The soil trays were then exposed to 60 mm of distilled water rain of high energy. At no aging (0.01d), runoff volume (a measure for seal development) and soil loss increased with the increase in AMC mainly because of enhanced slaking. Following aging the smallest runoff volume and soil loss were obtained at the intermediate AMC levels (2, 3 and 4 mm of water added). Furthermore, runoff and soil loss decreased with the increase in aging duration. At these AMC levels (generally between wilting point and field capacity), water-filled pores in the clay fabric were considered active in the stabilization process and the development of cohesive bonds between and within particles during the aging period. Soil erosion changed with the increase in aging duration in a manner similar to runoff, suggesting that runoff was the main precursor to erosion under these conditions.