جستجوی مقالات مرتبط با کلیدواژه "aggregate breakdown" در نشریات گروه "آب و خاک"

Splash erosion is the first type of water erosion caused by the impact of rain drops on the soil surface. Rain drops can disperse and move soil particles. Particles which transfer is effected by raindrop splash depends on several factors, including the soil type and the slope conditions. Although information on the role of these two agents splash erosion is available, but the selectivity of particles in splash erosion is a subject that needs further investigation, especially in the semi-arid region soils. This study was conducted to investigate the effects of splash erosion and selectivity of particles in different soils under the influence of slope. For this purpose, experiments were carried out in three different soils (Loam, Clay loam, Sandy clay loam) on four slopes (0, 10, 20 and 30%) under a simulated rain with constant intensity of 30 mm.h-1 in three replications, with a total of 36 units in the form of a completely randomized design. According to the results, the highest and the lowest amount of splash erosion were in the clay loam soil (105.07 g.m-2.min-1) and the sandy clay loam soil (80.28 g.m-2.min-1), respectively. With increasing the gradients, the intensity of splash erosion increased. In general, the selectivity of particles in the splash erosion was affected by the soil texture, the slope of the surface, and the interaction between of them. Silt was the most sensitive particle to splash, accounting for almost 57% of the splashed particles, and against the sand with almost 6% contribution to the splash was the most resistive particle. In all textures (except the loam texture), the selectivity of the silt particles at different levels of the gradient was greater than the rest. In the loam soil, clay particles were more selective than the silt particles, most likely due to the lower amount of clay particles in the original soil samples.

Rainfall erosion is the first type of water erosion on the land which is affected by various factors such as land use change and previous rainfall. This study was carried out to investigate the influence of previous rainfalls on the process of rainfall erosion in two marl soils (pasture and that changed to agriculture) under the simulated rainfall. Toward this goal, aggregate samples with the diameters of 6 to 8 mm were randomly collected from the marl areas in the west of Zanjan. Soil aggregates were packed into 48 boxes with the dimension of 30×40 cm to examine the effects of eight rainfall durations with three replications. Eight simulated rainfalls with the duration of 0, 7, 14, 21, 28, 35, 42 and 49 min and a constant intensity of 40 mm h-1 were used in the experiment. The soils were exposed to another simulated rainfall with 40 mm h-1 in terms of intensity for 15 min to study the rainfall erosion processes. The results showed that the aggregate breakdown was significantly affected by the previous rainfalls in the pasture soil (P<0.01), while there was no significant difference among the previous rainfalls in the case of agriculture soil.  Soil compaction and particles splash were significantly affected by previous rainfalls (P<0.05). Aggregate breakdown and particles splash were 1.41 and 1.31 times bigger than their values in the pasture soil. This study, therefore, revealed that the land use change in the mal areas increases the soil vulnerability to rainfall erosion processes. The rate of rainfall erosion processes in each rainfall event depends on the amount of previous rainfall. Increasing aggregate break down and soil water content by the previous rainfall could significantly influence the splash erosion rate in a marl soil.