Effect of natural rubber tire waste charcoal (NRTWC) on soil chemical properties in tea growing soils

Soil chemical properties are playing key roles in maximizing the production and quality of tea as well as sustainable management of tea-growing soils. Therefore, this study was carried out to assess the impacts of Natural Rubber Tire Waste Charcoal (NRTWC) application on major soil chemical properties in tea-growing soils. NRTWC was applied to a tea growing soil at different rates (0, 1, 1.6, 2.2 and 2.8% w/w) and soil chemical properties such as soil pH, organic matter content, NH₄⁺-N, NO₃^--N, available P and exchangeable K were assessed at 10 and 20 weeks after application of NRTWC. NRTWC amended soils showed significantly (P≤0.05) higher pH values for the application rates of 2.2% (5.85) and 2.8% (5.86) than the control where it recorded the lowest pH value (5.3) at the 20 weeks after application. According to the results, it was observed that the application of NRTWC that contained a large amount of organic carbon (~50%) contributed to a significant (P ≤ 0.05) increase in the organic matter content of tea-growing soils. The highest organic matter (5.58%) was recorded with 2.8% NRTWC application followed by 2.2% application (4.66%) 20 weeks after application. Furthermore, slow decomposition of the NRTWC increases total N (NH₄⁺-N and NO₃^--N), available P and exchangeable K content in the soils. Significantly (P≤0.05) higher NH₄⁺-N contents were observed for all the treatments at 20 weeks after the application of NRTWC compared to the control. However, amended soils showed significantly (P≤0.05) higher NO₃^--N contents for the application rates of 2.2 and 2.8% (3.9 and 6.9 mg kg^-1 soil, respectively) compared to the control (1.8 mg kg^-1 soil) at 20 weeks after application. The 2.8% application rate recorded the highest exchangeable K content at 10 weeks (143 mg kg^-1 soil) and 20 weeks (195 mg kg^-1 soil) after treatment application. As revealed by the results, NRTWC can be considered as a good source of soil amendment which could enhance soil chemical properties in degraded tea soils.