Estimation of soil loss in rubber (Hevea brasiliensis) growing areas of Kerala and Karnataka, India

Abstract

Soil erosion is viewed as a major process of land degradation in rubber-growing areas under hot moist sub-humid to humid agro-ecological region of Kerala and Karnataka in India. The bench mark survey with geo-reference at 121 locations was carried out with the objective of deriving soil-water conservation strategies in the extensive rubber-growing areas of Kerala and Karnataka (5.2 lakh hectares with productivity of 1514 kg/hectare). In the present study, Rainfall erosivity for 7 locations (considering monthly rainfall 1971 to 2007) and soil erodibility (Epipedons of 121 bench mark soils) were used. Monthly rainfall data, for the period 1971 to 2007 were used to compute the Modified Fournier index (MFI) The results showed that June, July and August receive maximum rainfall with very high Modified Fournier index (>160) from 433.4 (Trivandrum) to 2641.2 MJ mm ha−1 h−1 y−1 (Kannur) with an increasing from southward to northward. The soil erodibility (K) for five major soil subgroups of humults were 0.15 to 0.24 indicating that these soils are weakly susceptible to water erosion. Majority of the area (45.73% of TGA) is susceptible to extremely strong erosion followed by very strong erosion on 25.40 per cent of TGA and strong erosion in 22.28 per cent of TGA. The soil loss estimations can serve as effective inputs in prioritizing soil conservation strategies and management in rubber growing areas of Kerala and Karnataka.