Role of Wetting and Drying in Soil Aggregate Formation.

Naturally occurring wetting-and-drying cycles often enhance aggregation and give rise to a stable soil structure. Wetting-drying cycles works as the driving agents for transporting and depositing particle binding agents. Root mucilage material could play a significant role in the cementing of soil particles. The drying of soil increases bonding between SOM and sand as water is consumed, thereby bringing SOM into closer contact with the sand. The strength of an individual bond may be small, but they are additive. Consequently, the amount of mechanical stress that a soil can withstand will generally be increased by the presence of organic matter. Artificial soil aggregates that mimic the dynamic process that surrounds roots of desert grasses, where are aggregates are formed rapidly were created by using three types of sand (<70, 250 and 600 micron) and three type of polysaccharides (Xanthan, polygalacturonic acid (PGA) and Scleroglucan) with different concentration and different number of wetting drying cycles.

The results from the SEM images show that there is aggregate formed as a result of adding the polysaccharides and the aggregate stability were measured by turbidmetric method and wet sieving method which showed with increase the number of Wetting-Drying cycles the aggregates were more stable.