Impact of Diverse Agroforestry Systems on Soil Carbon Inventories and Microbial Activities in Indo-Gangetic Plains of Samastipur, Bihar

Abstract Land use significantly influenced in soil organic carbon (SOC) and its intricate dynamics, subsequently influencing various soil biochemical processes, as well as soil microbial and metabolic indices. This investigation aimed effect of different agroforestry systems (AFS) with diverse intercrops on soil carbon and pools and microbial properties up to 30 cm soil depth. The total organic carbon (TOC) content across the AFS in surface soils (0-15cm) ranged 8.75 to 11.45 g kg− 1. Poplar based AFS had 10.8 to 23.6% higher (p < 0.05) TOC while lowest in Semal (8.75g kg− 1). TOC decreased − 19 to -30.3% in subsurface (15-30cm) compared to surface soils. Very labile carbon (F1), labile carbon (F2), less labile carbon (F3) and non-labile carbon (F4) constituted 38.5, 15.3, 20.3 and 25.9% of TOC in surface soils and 34.1, 14.3, 22.1 and 29.4% in subsurface soils. Poplar based AFS had higher Basal Respiration (25.2%) while lowest (0.475 µg CO2-C g− 1 h− 1) in Mango. Poplar recorded higher Carbon Management Index in surface (209.73%) and subsurface (178.5%). Principal component analysis has shown the first two PCs represented 82.69% of the total variation wherein TOC was the most influential factor in PC1 and microbial metabolic quotient (qCO2) in PC2. Overall, Poplar based AFS outperformed among AFSs. So, therefore, we suggest, promotion of poplar-based systems to restore soil carbon and microbial properties as well as overall soil health while ensuring nutritional security of the Indo-Gangetic plains of Samastipur.