Role of Clay-humus Complexes in Soil Organic Carbon Stabilization Across Paddy Soils in Diverse Indian Soil Orders

Abstract

Aims: This study investigates the mechanisms of soil organic carbon (SOC) stabilization within clay-humus complexes across diverse soil orders in Indian paddy soils. By employing FTIR spectroscopy and NaOCl oxidation, it examines how different clay mineral compositions, such as smectite-rich Vertisols, influence SOC stability. Place and Duration of Study: Soil samples were collected from paddy-growing regions in India- Entisol from Nadia (West Bengal), Inceptisol from Sonipat (Haryana), Vertisol from Belgaum (Karnataka), and Alfisol from Davanagere (Karnataka), between June 2019 and July 2020. Methodology: Soil samples were collected from paddy-growing regions across four Indian soil orders: Entisol, Inceptisol, Vertisol, and Alfisol. SOC stabilization was analyzed through X-ray diffraction (XRD) for mineral composition, total and NaOCl-resistant carbon measurements, and FTIR spectroscopy to characterize functional groups in humic acids and clay-humus complexes. Results: The study found that Vertisol soils, with higher smectite content, showed the highest level of total and stable carbon, while Alfisols, dominated by kaolinite, exhibited lower stability. FTIR analysis indicated strong aromaticity in Vertisol's humic acid, suggesting enhanced stability through complex mineral interactions Conclusion: This research highlights the crucial role of soil mineralogy in SOC stabilization, with significant implications for carbon sequestration strategies in Indian paddy soils. These findings could support targeted soil management practices for enhancing SOC retention and promoting sustainable agriculture.