Influence of Land Uses on Soil Carbon Mineralization in Selected Agro-ecological Units of South Kerala, India

Abstract

Soil is a major reservoir of terrestrial carbon and it plays an important role in the global                        carbon cycle. The soil organic carbon (SOC) is the fundamental factor for sustainable agriculture because of the ability in maintaining the soil fertility which is critical to soil productivity. Soil carbon pool has gained paramount importance in the recent decades owing to the alarming issues of climate change and global warming. Land use change was found to have a larger net effect on SOC storage than projected climate change. Depending on the land use management practices, soils can be a net sink or source for CO2. In this regard the present study was carried out to assess the impact of different land uses on carbon storage and mineralization in soils of selected agro-ecological units of south Kerala.The agro-ecological units (AEUs) of south Kerala namely, southern coastal plain (AEU 1), Onattukara sandy plain (AEU 3), southern laterites (AEU 8), south central laterites (AEU 9) and southern and central foothills (AEU 12) were selected. In each AEU, different agricultural land use categories as described by IPCC for the carbon inventory such as, garden land (coconut), wet land (rice), fallow (uncultivated) and plantation (rubber) were also selected for the study. The potential for carbon mineralization in soil was assessed by evaluating factors such as Total organic carbon, mineralizable carbon, particulate organic carbon, global warming potential, carbon distribution, and turnover. The total organic carbon and particulate organic carbon were higher in rubber land use and AEU 12. The mineralizable C content in soil varied from  1.40 to 3.45, 1.18 to 3.41, 1.04 to 3.04, 1.23 to 3.35  and 1.01 to 3.02 mg g⁻¹ in AEU 1, 3, 8, 9 and 12 respectively. The highest value was observed from AEU 1 and rice land use. Similar trend was obtained for global warming potential of soils based on CO2 evolution which varied from 31.82 to 78.41, 26.89 to 79.02, 22.89 to 69.02, 28.03 to 76.06 and 22.96 to 68.64 in AEU 1, 3, 8, 9 and 12 respectively. The C proportion and turnover rates were in the range of 0.25 to 0.77 and 0.04 to 0.17 respectively. The C proportion was the highest in AEU 12 and rubber land use whereas the C turnover was the highest in AEU 1 and rice land use.