اثر ويژگيهاي فيزيكي و شيميايي بر فرسايش پذيري در خاك هاي آهكي

Effect of Physicochemical Properties on Erodibility in Calcareous Soils

Soil erodibility defines the resistance of the soil to both detachment and transport. This factor may be affected by some soil physicochemical properties. This study was conducted to determine physicochemical properties affecting the erodibility (K factor) in calcareous soils. The study was conducted in the Hashtrood, located in northwestern Iran, from March 2005 to March 2006. The study soils had almost 13% lime and 1% organic matter. In order to investigate, the square network of agricultural soils with 900 km2 in area was selected and divided into 36 regular grids. In each grid, the erosion plots designed agreement to unit plot at 3 replicates with 1.2 m spacing. The physicochemical soil properties consited of sand, coarse sand, very fine sand, silt, clay, gravely organic matter, lime (TNV), potassium, aggregate stability and permeability were measured in the study soils. The soil erodibility was measured based on annual soil loss amount per unit rainfall erosivity factor. The soil loss at the unit plots was affected by 23 natural rainfall events during the study period. Avereage soil loss and soil erodibility in the study area were 1.868932 t/ha. year and 0.004258 t.h/MJ.mm respectively. The soil erodibility significantly was affected by sand, silt, organic matter, lime, aggregate stability and permeability. Silt contrary to sand, organic matter, lime aggregate stability and permeability increased the soil erodibility. Correlation between the soil erodibility and clay, gravel- and potassium was not significant. Study of effect of the physicochemical properties on the erodibility with principal component analysis method revealed that the soil erodibility mainly is affected by permeability, clay and lime. These soil properties significantly (Rz=0.84, p<0.001) decresed the soil erodibility.