Variability of Soil Properties under Different Land Uses in Sub-humid Tropical Region of West Bengal, India

摘要

In this study, depth wise (0-20 cm and 20-40 cm) soil organic carbon (SOC), total nitrogen (N), particulate organic matter carbon (POMC), humus carbon, humic acid fraction, optical densities at 465 nm and 665 nm (E4/E6) of humus fraction were quantified under forest, tea, fallow (permanent) and cultivated land situated in Terai (plain) region, West Bengal, India. The results showed variation in SOC, bulk density, total N, and POMC and humus carbon in relation to above said land use systems. The forest soils had the lowest bulk density (1.35 Mg nr3) at surface followed by tea. The SOC in all types of land uses were 1.8 to 5.1 times lower than forest. The decline in SOC between surface and sub-surface soil depth within any land use was in the range of3.4 to 32.4%. The mean content of POMC to SOC was around 25.5%. Regression of POMC vs. SOMC across sites showed better linear relationships in surface (R2=0.74) than sub-surface (R2=0.57). Higher amount of humic acid was found in forest soils as compared to other systems. On an average, the value of E4/E6 ratio of humic acid was 58.7 per cent lower than the E4/E6 ratio of fulvic acid showing a high degree of condensation of humic substances in humic acid than in fulvic acid.