Temporal Variations of Aggregates Breakdown and Splash Particles Processes in a Marl Soil Under Simulated Rainfall

Aggregate breakdown and splash particles are the most important results of raindrops impact on soil surface. The study was conducted to investigate the temporal variations of breakdown and splash processes in a virgin marl soil in Zanjan Province. The experiment was carried out as a completely randomized design with eight rainfall duration treatments and three replications, in 2010. Twenty four flat boxes with dimensions of 30 cm× 40 cm were filled with soil aggregates (6-8 mm). The aggregates boxes were placed under a rainfall simulator with a constant intensity of 40 mm h-1.The aggregate breakdown values was obtained based on comparison of the mean weight diameter of the aggregates before and after rainfall events. The splash values were determined from the dry weight of soil particles that had splashed out around the boxes during each rainfall event. Based on the results, there were significant relationships between the rainfall duration and both the aggregate breakdown (R2= 0.99, p<0.01) and the particles splash (R2=0.95, p<0.05). The aggregate breakdown value was low at the beginning of rainfall (7.5 min), but it increased with increasing rainfall duration and, subsequently, soil surface was crusted in 45 min. At this time, aggregate breakdown and particles splash values were almost maximized. After 45 min, aggregate breakdown and particles splash values were negligibly increased due to crust formation at soil surface. There was a significant relationship between the particles splash and the aggregate breakdown (R2=0.98, p<0.05).