Assessment Of Soil Erosion From Different Land Use Types Using ¹³⁷Cs Technique In Xiashiziwan Watershed,Lingbao,Loess Plateau

Starting from the time of agricultural activities in the Xiashiziwan watershed,Henan province,China,the land gradually declined due to erosion as pollution was seen in the reservoirs of the watershed.Sediments and agricultural nutrients reach the reservoirs through runoff and soil erosion.Over the last decades,soil and water conservation measures,such as re-vegetation terracing and conservation tillage,are practiced for controlling of water erosion and sedimentation.However,no more research has been conducted to evaluate the extent of soil erosion and examine how land use types,slope gradient and soil particle size affects soil erosion rate and the general impact of soil erosion on SOC content.Therefore the objective of this study was to understand about those questions and look for further soil water conservation measures and watershed management as a whole to secure the land for having better agricultural productivity.It was done by quantifying the soil and sediment loss from different land use types and identifying the areas at risk,using ¹³⁷Cs measurements.The watershed was divided in to 7 land use types using Geographical Information System?GIS?,presenting specific slope-land use type combinations.Representative fields from each land use types were sampled for¹³⁷Cs and other soil physical properties?Soil moisture and bulk density,particle size,soil organic matter?.Using the area coverage the data for individual fields were extrapolated to land use types and the whole watershed area.Based on this approach,it was estimated that the 21 composite samples classified into five classes of soil erosion,some twelve samples indicated a net soil loss,with an average of-75.56 t ha^-1yr^-1 and the other nine profiles were considered as having experienced soil deposition,with an average value of 22.76 t ha^-1 yr^-1.The average annual sediment production is estimated to be 12561 t;though around 22633 t of gross soil erosion was estimated.Slopping agricultural lands with a slope of 15^o were estimated to have the highest sediment rate(141.8 t ha^-1 yr^-1)for an annual sediment production of2558.07 t,followed by the same land use type of different slope?7^o?,112 t ha^-1 yr^-1,however the terraced land with a slope length of 10m;with a net sediment production rate of 46.5 t ha^-1 yr^-1 ranked first for annual sediment production which is nearly 40%of the overall sediment production for the fact that it covers the largest area.The forest land was seen to resist erosion though the topography is steep for the reason that vegetation cover reduces erosion rate.Terraced land with a slope length of 4m and orchard land were found to be responsible areas for soil deposition with;11.7 and 4.1 t ha^-1 yr^-1respectively,where as the slopping agricultural land 15^o of slope experienced with soil loss 141.8 t ha^-1yr^-1.Hence slopping agricultural land with a slope of 15^o can not only be changed to forest but also to orchard or terraced which can increase economic benefits compared with forest land.The results implied,slope-land use combination management is very important for land use planning at the watershed to protect the area from soil erosion.Soil organic matter content results implied that SOC inventories increases with decreasing soil erosion at the watershed level scale.