Investigation and comparing gully erosion characteristics in agriculture and rangeland land uses, case study: Robat Tork watershed

Gully erosion is a type of water erosion which causes degradation in both agricultural fields and rangelands as well in arid and semi-arid areas. According the role of soil degradation due to erosion، research objectives were to find out investigation causes gully erosion in Robat Tork Watershed. In this research three representative gullies were selected in agriculture and rangeland working units. In each working unit، samples taken from nine soil profiles were analyzed for texture، organic matter، gypsum، total lime، pH، EC and SAR. Soil infiltration rate was measured where were drilled profiles in each working unit too، In addition، morphometric characteristics of gullies including length and lateral profiles، top and down width، depth of gully، the cross section، width to depth ratio، the slope of bed، gully length were studied. Results of the study showed that SAR and sodium cation are caused dispersion of soil particles and increasing gully erosion. percentage of clay and silt is 11% and 29% in surface layer representative head cut gully and organic matter is between 0. 30% to 1. 82% in agriculture unit. In rangeland unit، percentage of clay and sand is 41% and 43% in surface layer representative head cut gully and organic matter is between 0. 29% to 0. 99%. In rangeland unit، in a specified level، the number of gully is more than agriculture unit. Furthermore، the results showed that TNV in agriculture unit and pH، EC in rangeland unit is more than. In both units depth to wide ratio is more than 1 in every gully. Permeability of soil is 4. 25 cm and 3. 45 cm in agriculture and rangeland units respectively.