Soil erodibility evaluation by splash cups under the simulated rainfalls

Soil erodibility is an important parameter to determine the sensibility of soil to the erosion and there are many methods to specify the erodibility. Until today, many methods were improved and the “Universal Soil Loss Equation (USLE), which has the most common use in worldwide, is one of them. In this prediction technology, the soil susceptibility to the water erosion is represented by a multiplier factor together with those for climate, topography, vegetation and conservation practices. This study aimed to determine a soil erodibility factor by the laboratory simulated rainfall tests under the specified kinetic energy and rainfall intensity values using the splash cups. For test soils, a total of 256 surface samples were taken from the fallow-crop system in the Asartepe Dam Basin and the splash erosion rate was found with the units compatible with the USLE. However, since the USLE predicts soil losses from not only splash erosion but also sheet and rill erosions, the measured splash values should be mathematically related to the erodibility equations commonly employed in the model in order to meet the model requirement

The effects of land use changes on some soil properties in Indagi Mountain Pass - Cankiri, Turkey

Understanding spatial variability of dynamic soil attributes provides information for suitably using land and avoiding environmental degradation. In this paper, we examined five neighboring land use types in Indagi Mountain Pass-Cankiri, Turkey to spatially predict variability of the soil organic carbon (SOC), bulk density (BD), textural composition, and soil reaction (pH) as affected by land use changes. Plantation, recreational land, and cropland were the lands converted from the woodland and grassland which were original lands in the study area. Total of 578 disturbed and undisturbed soil samples were taken with irregular intervals from five sites and represented the depths of 0-10 and 10-20 cm. Soil pH and BD had the lower coefficient of variations (CV) while SOC had the highest value for topsoil. Clay content showed greater CV than silt and sand contents. The geostatistics indicated that the soil properties examined were spatially dependent to the different degrees and interpolations using kriging showed the dynamic relationships between soil properties and land use types. The topsoil spatial distribution of SOC highly reflected the changes in the land use types, and kriging anticipated significant decreases of SOC in the recreational land and cropland. Accordingly, BD varied depending on the land use types, and also, the topsoil spatial distribution of BD differed significantly from that of the subsoil. Generally, BD greatly decreased in places where the SOC was relatively higher except in the grassland where overgrazing was the more important factor than SOC to determine BD. The topsoil spatial distributions of clay, silt, and sand contents were rather similar to those of the subsoil. The cropland and grassland were located on the very fine textured soils whereas the woodland and plantation were on the coarse textured soils. Although it was observed a clear pattern for the spatial distributions of the clay and sand changing with land uses, this was not the case for the silt content, which was attributed to the differences of dynamic erosional processes in the area. The spatial distribution of the soil pH agreed with that of the clay content. Soils of the cropland and grassland with higher amounts of clay characteristically binding more cations and having higher buffering capacities had the greater pH values when compared to the soils of other land uses with higher amounts of sand naturally inclined to be washed from the base cations by the rainwater

Splash detachment of sand particles under varying contact stress field of wind-driven raindrop impact

The effects of wind-driven rain (WDR) on sand detachment were studied under various raindrop obliquities. Results suggested a significant reduction in compressive stress on sand surfaces for a two-dimensional experimental set-up in a wind tunnel. During experiments, sand particles in splash cups were exposed to both wind-free rain (WFR) and WDR driven by horizontal winds of 6.4, 8.9 and 12.8 m s(-1) and rainfall intensities of 50, 60, 75 and 90-mm h(-1) to assess the sand detachment rate (D, in g m(-2) s(-1)). The effects of sand moisture state (dry and wet) on the detachment of different-sized particles (0.20-0.50 and 0.50-2.00 mm, respectively) were also tested. Factorial analysis of variance showed that shear and compressive stress components evaluated by horizontal and vertical kinetic energy flux terms (KEx and KEy, respectively, in J m(-2) s(-1)) along with their vector sum (KEr, in J m(-2) s(-1)) explained the variation in D. Neither sand size nor sand moisture was statistically significant alone although binary interactions of KEr, KEx and KEy with the sand size and three-way interaction of KEx, sand size and moisture were statistically significant. These results can be explained by size-dependent variation in sand compressibility and surface friction related to the total stress field developed by a given partition of shear and compressive stresses of wind-driven oblique raindrops (KEx/KEy). Further analysis of the variation of the unit sand detachment rate (D-u = D/KEr = g J(-1)) with rain inclination (alpha, in degrees) better revealed the effect of WDR obliquity on D-u that further changed with sand size class and moisture state. Finally, the difference in the resulting stress field differentiable by the oblique raindrop trajectories of the experiment over sand surface significantly affected the non-cohesive particle detachment rates, to some extent interacted with size-dependent compressibility and interface shear strength of sand grains