Divergent models of biomass accumulation, carbon sequestration, and carbon credit potential in reclaimed sodic lands

Carbon sequestration in soil and perennial trees biomass is vital for soil health, ecosystem resilience, and climate change mitigation. This study assessed the five diverse land use systems for soil carbon dynamics, biomass production, carbon sequestration and carbon credit generation in the western Indo-Gangetic Plain (IGP) of India. The systems were (1) Conventional agriculture system (rice-wheat system) (LU-CA); (2) Partial conservation agriculture system (zero tillage direct seeded rice - zero tillage wheat with 1/3 rd crops residue retention) (LU-PCA); (3) Litchi-based horticultural system ( Litchi chinensis ) (LU-LHS); (4) Melia-based agroforestry system ( Melia dubia + wheat) (LU-MAS); and (5) Eucalyptus based plantation system ( Eucalyptu s spp.) (LU-EPS). Soil samples from four depths (0-15, 15-30, 30-45 and 45-60 cm) were collected and analysed for physico-chemical properties, carbon fractions, carbon management indices, and sequestration potential. The SOC stock in LU-EPS, LU-LHS, LU-PCA and LU-MAS was 79.4, 39.6, 22.9 and 20.8% higher compared to LU-CA. The passive carbon pool was 207.4% higher in LU-EPS than LU-CA, whereas LU-PCA increased the active carbon pool by 32.2%. The LU-EPS exhibited the highest recalcitrant index (RI), signifying enhanced carbon stability. LU-EPS produced highest total biomass (631.4 Mg ha -1 ), and demonstrated the highest CO 2 equivalent sequestration potential (109.9 Mg CO 2 eq. ha -1 ), exceeding LU-CA by 191.5%. Compared to conventional rice-wheat system, diverse land use systems generated carbon credits ranging from 93.1 to 1577.5 US$ ha -1 yr -1 . The Random Forest regression model demonstrated robust predictive performance for total biomass, soil organic carbo (SOC) stock, total carbon stock, and carbon sequestration rate (CSR), with land-use emerging as the most influential factor across all variables. These findings highlight the significant potential of agroforestry and tree plantation in enhancing SOC sequestration, stabilizing carbon pools, and generating carbon credits for sustainable agroecosystem management.