Abstract

                                A study was conducted in different agroclimatic zones of Tamil Nadu with the objective of assessment of Soil Organic Carbon (SOC) stock and its changes overtime, prediction of SOC stock under existing and alternate cropping pattern using Roth C model. Fifteen benchmark soils were selected in different agroclimatic zones of Tamil Nadu based on their land use and areal extent to assess SOC level and its changes overtime. Results revealed that, during 1997 and 2007 SOC was higher in forest ecosystem of pedon 15 (Ooty series) and in pedon 14 (Pechiparai series) of horticultural land use. Among seven agroclimatic zones of Tamil Nadu soil series in five agroclimatic zones viz., eriyanaickenpalayam series (Western zone), Peelamedu series (Southern zone), Vallam series (North eastern zone), Vannappatti series (North western zone) and Padugai series (Cauvery delta zone) were selected to predict SOC stock for the year 2025 and 2050 except hilly and high rainfall zone due to high organic carbon content in these agroclimatic zones. Results showed that, among the soil series selected for the study, Vannappatti and Padugai series registered the highest Total Organic Carbon (TOC), Biomass Carbon (BIO) and Humified Organic Carbon (HUM) under existing cropping pattern while Periyanaickenpalayam, Peelamedu and Vallam series had high TOC, BIO and HUM under alternate cropping pattern. Among five selected soil series, Periyanaickenpalayam, Peelamedu and Padugai series recorded 7.5 g kg-1 TOC during 2025 and 2018, 2100 and 2035, 2013 and 2014 under existing and alternate cropping pattern respectively.

Key words : Soil organic carbon (SOC), land use, benchmark soil, agro climatic zones, Roth C model.