Soil Organic Carbon Pools as affected by Sixteen-Year-Old Mango, Litchi and Aonla Orchards in Calciorthents of Eastern India

Abstract

The present investigation was conducted with sixteen-year-old Mango, Litchi and Aonla orchards established at Krishi Vigyan Kendra, Birouli, Samastipur (Bihar) to study the distribution of soil organic carbon into different pools of varying lability in surface (0-15 cm) and sub-surface (15-30 cm) soil layers. Fruit orchards were Mango (Mangifera indica) var. Malda, Litchi (litchi chinensis) var. China and Aonla (Emblica officinalis) var. NA-7. Total SOC, oxidizable SOC, soil inorganic carbon (SIC), four pools of SOC, and carbon management index (CMI). All the orchards significantly improved SOC showing 13 to 44 % higher than that in the open (without trees). The total SOC stock up to the soil depth of  0-30 cm in the soil profile was found to be higher in the fruit orchards as compared to the open (without trees) and followed the order: Aonla (31 Mg ha^-1) > Litchi (29 Mg ha^-1) > Mango (28 Mg ha^-1). The SIC of the soil followed a reverse trend with the SOC. All the orchards had significantly lower SIC as compared to the open. Aonla orchard had significantly lower SIC followed by Litchi and Mango. Per cent contribution of SOC pools to the total SOC followed as: Non labile (47 %) > Very labile (25 %) > Labile (16 %) > Less labile (12 %). The ‘r-value of total SOC varied significantly with its different fractions and decreased in the order of VLC (r = 0.955**) > LLC (r = 0.952**) > LC (r = 0.896**) > NLC (r = 0.762**). Among the orchards, Aonla orchard showed the highest CPI (1.234), followed by Litchi (1.154) and Mango (1.101). The mean CMI ranked as Aonla orchard (149.9) > Mango orchard (138.1) = Litchi orchard (137.8) > Open (115.0). Among the orchards, Mango orchards showed the maximum LI (1.254), followed by Aonla (1.216) and Litchi (1.196), irrespective of the soil depths. Surface soils showed significantly more LI than that of sub-surface. Thus, the Aonla orchard may be considered the best orchard production system to sequester carbon. Hence, its promotion and expansion as land-use practices in the calcareous belt of north Bihar will be helpful for food security and mitigating climate change.