Methodological problems of soil erosion research on intensively Cultivated fields in the monsoonal climate of NE India using 1,7 Cs radionuclide

The estimation of soil erosion rates in complex tropical agricultural systems is difficult and most of the traditional methods have serious limitations. The ¹³⁷Cs technique allows to obtain relatively quickly retrospective medium term soil erosion results. The spatial variation of soil erosion rates was studied, in a small catchment under intensively cultivatcd fields and permanent grasslands on the hilly Meghalaya Plateau in India, using the ¹³⁷Cs technique. The measurcd values of cesium inventory for all sampling points are between 3% and 70% of the reference value of cesium inventory. The estimated annual soil loss depends strongly on the model used to calculation. It is visible that value obtained by simplified mass balance model (7.9-78.9 Mg·ha⁻¹·a⁻¹) and improved mass balance model (6.3-72.3 Mg·ha⁻¹·a⁻¹) are quite similar (whereas the value of soil erosion obtained by proportional model (5.6-18.1 Mg·ha⁻¹·a⁻¹) are far away from mass balance models. In case of grassland the diffusion-migration model was used and obtained results of soil erosion are lower than 0.5 Mg·ha·a⁻