Moderate grazing is the best measure to achieve the optimal conservation and soil resource utilization (case study: Bozdaghin rangelands, North Khorasan, Iran).

Abstract

The study of the variability of physical and chemical factors of soil due to different intensities of livestock grazing can help in the management and maintenance of soil and vegetation. Accordingly, the effect of livestock grazing intensities on soil properties and vegetation in Bozdaghin rangelands of North Khorasan province was investigated. To investigate the effect of different livestock grazing intensities, Three 5-hectare plots in the study area were determined under different treatments (ungrazed (UG), moderate grazing (MG), and heavy grazing (HG)), and the effect of three grazing intensities on vegetation and soil physicochemical and erodibility properties (SPEP) was evaluated. The soil sampling process was performed at depths of 0-15, 15-30cm and SPEP including soil saturation moisture (SSM), soil texture (percentage of clay, sand, and silt), absorbable potassium (K), electrical conductivity (EC), soil organic matter (SOM), absorbable phosphorus (P), acidity (pH), and bulk density were evaluated, and Soil Erodibility Index (SEI) was calculated by implementing the modified clay ratio relation. To assess the impact of various grazing intensities on all measured characteristics, multivariate analysis of variance (MANOVA) and Duncan tests were utilized to compare the means and their grouping. The results showed that HG compared to MG causes worrying consequences in the first soil depth. Also with increasing grazing intensity, plant production percentage (P <0.05) and vegetation density (P <0.01) decreased, and the amount of bare soil (P <0.01) increased. Also, with increasing grazing intensity, the amount of pH, EC, clay, saturated moisture, and N decreased (P < 0.01), but the amount of silt, sand, K, P, calcium (Ca), lime, and SOM increased (P <0.01). UG improves soil quality, MG intensity causes optimal conservation and utilization of soil resources, and HG intensity causes severe changes in rangeland soil properties. In areas with MG intensity, due to the increase of the percentage of vegetation (an increase of SOM and prevents the direct impact of raindrops on the soil aggregates) and as a result improvement of soil structure and texture, an increase of water infiltration, and decrease of runoff, and the rate of soil erodibility and water erosion, the rangeland soil decreases and results in sustainable production. This results in optimal conservation and utilization of soil resources. So to sustainably exploit and balance the conservation of biodiversity, livestock production, and soil carbon and nitrogen management, MG is recommended.