Natural Rubber Tire Waste Charcoal (NRTWC) on Organic Carbon Mineralization in Tea Growing Soils

The aim of this study was to assess the impact of natural rubber tire waste charcoal (NRTWC) amendment on carbon mineralization in tea cultivated soils in low country wet zone of Sri Lanka. NRTWC was applied at different rates (0%, 1%, 1.6%, 2.2% and 2.8% w/w) and carbon mineralization in soil was evaluated at 10 and 20 weeks after the treatment. Representative samples were incubated for 42 days and microbial respiration was determined. During the first seven days of incubation, a rapid carbon mineralization was observed for all the treatments. A rapid decline of carbon mineralization was then observed during the period from 14^th to 28^th day of incubation. No changes were observed towards the end of the incubation (35 to 42 days). Significant (P ≤ 0.05) differences among the different rates of NRTWC application were noticed during the initial stages of the incubation. However, the variations were minimal after 14th day of the incubation. The cumulative carbon mineralization ranged from 506 to 1072 mg/kg soil for the samples taken at 10 weeks after treatment. The corresponding variation changed from 506 to 1730 mg/kg soil for the samples drawn at 20 weeks after treatment. The cumulative soil carbon mineralization increased rapidly during the early stages, then decreased gradually and finally flattened out towards the end of the incubation. The application of NRTWC resulted in a substantial increase in cumulative carbon mineralization when compared with the control. As revealed by the results, NRTWC decomposes slowly and can be considered as a sound source of soil amendment which could enhance soil carbon sequestration in degraded tea soils.