GIS-BASED MODELING OF CAESIUM-137 CONTENT IN SOIL MATERIAL APPLIED TO COMPUTE PLOWED SOIL LOSSES

Abstract. The paper describes and discusses possibilities for soil loss estimation in the area of an arable slope using the radiocaesium method, GIS-based analysis, and very high resolution satellite imagery. The interdependences between caesium-137 activity, catchment area value, and the (sign of) profile curvature were estimated using GIS facilities. Interdependencies were estimated for four zones of an agricultural field located in the basin of the Sukhaya Orlitsa River in the Oryol district of the Oryol region (central part of European Russia). The zones were delineated according to differences of surface structure. Special attention was paid to the analysis of the caesium-137 and humus lateral and vertical (in the 0–25 cm arable soil layer) distribution in the area of agricultural field located on the slope of southern exposure. Overplowed soils were detected in one of the delineated zones. Overplowed soils are a type of degraded soils. This soil type was formed under conditions of applying a small amount of fertilizers for the period from 1991 to 2017 in agricultural fields remote from the central estates. In the studied area, the humus content in the arable horizon of plowed gray forest soil was reduced to 4%. The specific activity of caesium-137 does not exceed 140.0 Bq/kg (with its value at the reference plot of 174.7 Bq/kg). The radiocaesium method and estimations of morphometric parameters of topographic relief applied to the computation of soil runoff rate, made it possible to formalize the description of soil losses depending on in-the-relief position of the point, and to compile maps of soil runoff for each of the zones in the field. It was found that the area of overplowed soils is characterized by the largest soil losses (reaching 20 t/ha per year or more). Compiled map can allow to undertake a differentiated approach to the reclamation arrangement of the territory in the analyzed area. If enough fertilizers are applied, the productivity of the overplowed soils can be restored in the future.