EVALUATION OF TOBACCO BASED LAND USE SYSTEMS - EFFECTS ON SOIL ORGANIC CARBON DYNAMICS AND CARBON MANAGEMENT INDEX

Abstract

Six contrasting land use systems including Eucalyptus, Oil Palm, Sugarcane, Fallow – Tobacco, Paddy – Tobacco and Green manure (Sunnhemp) Tobacco were evaluated for their effects on soil carbon (C) storage, stratification, C fractions and carbon management index (CMI). The total organic carbon (TOC) content was significantly greater in surface soil layer (0.00-0.15 m) under all the land use systems and showed a decreasing trend with increase in soil depth. The TOC in 0.00-0.05 m soil layer was maximum under Oil Palm (8.52 g/kg) while it was minimum in Fallow- Tobacco system (3.54 g/kg). The highest and the lowest soil organic carbon storages were recorded by Eucalyptus system (34.77 Mg/ha) and the Fallow - Tobacco system (20.46 Mg/ha), respectively. The labile fraction of SOC also showed a decrease with increasing soil depth. The Oil Palm system that received organic manures showed relatively large quantity of labile carbon (CL) (480 mg/kg) in surface soil (0.00-0.05 m). The CMI, an index of soil quality, was the highest (71) under Eucalyptus system and the lowest (35) in Fallow-Tobacco system at surface layer as compared to the forest soil as reference having CMI value of 100. Stratification ratio of TOC for Green manure (sunnhemp) – Tobacco system has uniform values at all the depths, indicating that this system has maintained uniform TOC at all depths. The lowest SOC storage as well as CMI observed in Fallow – Tobacco may be attributed to the fact that entire plant biomass (leaves, stems and roots) is generally taken off the field. This study demonstrates that the monocropping (Fallow – Tobacco) of tobacco leads to a depletion of soil organic carbon and its quality, and hence calls for use of organics at liberal rates for sustaining the soil quality and production sustainability.