Pragati Pandey, S.P. Singh, U.P. Shahi, Jairam Choudhary, Kamlesh Kumar, P.K. Singh and Purushottam
Abstract
Cropping system diversification is an important strategy for improving soil carbon sequestration and sustaining soil health in the Indo-Gangetic Plains. The present study evaluated the effect of six cropping sequences, viz., Fallow, Rice-Wheat, Cotton-Wheat, Pearl Millet-Wheat, Rice-Berseem and Pigeon pea Wheat, on soil carbon fractions and carbon stabilization under western Uttar Pradesh, India. Surface (0-15cm) and subsurface (15-30 and 30-45 cm) soil samples were analyzed for very labile carbon (VLC), labile carbon (LC), less labile carbon (LLC), non-labile carbon (NLC). Cropping sequences significantly influenced all soil carbon fractions across soil depths. Pigeon pea-Wheat recorded the highest VLC and LC, indicating greater accumulation of biologically active carbon due to enhanced residue inputs and rhizodeposition. In contrast, RiceâWheat exhibited significantly higher LLC and NLC, reflecting greater stabilization of soil organic carbon under submerged rice cultivation. Active and passive carbon pools, together with carbon management indices, were markedly improved under diversified cropping systems compared with the fallow treatment. Irrespective of cropping sequence, all carbon fractions decreased with increasing soil depth. The findings demonstrate that legume-based diversification enhances the active carbon pool, whereas rice-based systems favor the stabilization of recalcitrant carbon fractions, thereby contributing to improved soil quality and long-term carbon sequestration in the Indo-Gangetic Plains.