The Effect of Land use and Soil Erosion on Soil Organic Carbon and Nitrogen Stock

  Soil organic carbon (SOC) is a principal component in soil quality assessment. Knowledge of SOC and total nitrogen (TN) stocks are important keys to understand the role of SOC in the global carbon cycle and, as a result, in the mitigation of global greenhouse effects. SOC and TN stocks are functions of the SOC concentration and the bulk density of the soil that are prone to changes, influenced by land use changes, and soil erosion processes. This study has evaluated SOC and TN stock under different land use types and soil erosion types at catchment scale.SOC and TN stocks were measured in 112 different sampling sites of four main groups of land use/soil erosion: rangeland/surface erosion, orchard/surface erosion, dry-farming land/surface erosion, and rangeland/streambank erosion at Hiv and Zidasht catchments, Iran. The results showed that SOC and TN stock under all land use and erosion groups was significantly different. SOC and TN stock was greatest in the orchard land use and the total SOC stock for the 20 cm soil layer under different land uses and erosion types varied for Hiv in order of orchard/surface erosion (46), rangeland/surface erosion (31), and rangeland/streambank erosion Mg/ha (p<0.005).  For Zidasht, the variance was, in order:orchard/surface erosion (43), dry-farming land/surface erosion (23), rangeland/surface erosion (23), and rangeland/streambank erosion 22 Ton/Hector (p<0.005). The TN stock has the same trend in all studied land use and erosional groups. Therefore it was concluded that rangelands were affected by erosion, with a subsequent decreasein productivity level. These results can be useful as a scientific basis for selecting the proper soil erosion control methods as a simple, low-cost approach to mitigate SOC and TN loss.