Effects of the Number of Wetting-Drying Cycles on Structure Stability, Particle Size Distribution and Pore System of Soil

Document Type : Research Paper


Assistant Professor, Soil Science. College of Agriculture., Bu-Ali Sina University, Hamadan, Iran


Soil wetting and drying cycles are important environmental processes that often act as mechanisms of soil pore system change. Also, clay and organic matter contents are two of the soil intrinsic properties involved in soil structure building properties. The aim followed in this study was to investigate the relationship of a number of wetting and drying cycles, clay content and soil organic matter with the soil structure stability, particle size distribution as well as soil pore system. Some soil physical properties were determined after one (T1), three (T3) and five (T5) wetting and drying cycles and compared with the aggregate stabilities of initial untreated soils (soil undergoing no wetting and drying cycles). The results showed that the improvement in aggregation was most pronounced in the clayey soils especially when containing a high level of organic matter. Following once and thrice wetting and drying cycles, only two clay soil samples more aggregated than soils with less clay content; but further wetting and drying cycles (5 cycles) resulted in a decrease in stability of aggregates. The findings indicated that the macro aggregation depended mostly on soil texture attributes rather than organic matter content; and the former were more effective in aggregating when combined with high amount of clay content. Also it became evident that the compaction caused by sampling could be amended through wetting and drying cycles and the alternation of these cycles is an important mechanism for soil structure improvement.


Main Subjects

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