Impact of Natural Rubber Tire Waste Charcoal on Selected Soil Physical Characteristics of Tea Growing Soils

The present study assessed the impact of application of natural rubber tire waste charcoal (NRTWC) on selected physical characteristics of tea cultivated soils which belongs to Red Yellow Podzolic great soil group. Natural rubber tire waste charcoal was applied as a soil amendment at different rates (0%, 1%, 1.6%, 2.2% and 2.8% w/w). Physical attributes of soil; bulk density, particle density, porosity, texture and aggregate stability were assessed at 10 and 20 weeks after application of NRTWC. Natural rubber tire waste charcoal significantly improved physical characteristics of soil by reducing soil bulk density, and increasing particle density, porosity and aggregate stability. Natural rubber tire waste charcoal treated soils showed significantly (p ≤ 0.05) lower bulk densities for the application rates of 2.2% and 2.8% (1.21 and 1.17 gcm-3 respectively) compared to the control (1.39 gcm-3) at 10 weeks after application. Significantly (p ≤ 0.05) lower particle density was observed for the application rate of 2.8% (2.52 gcm-3) than the control at 20 weeks after application. The increased porosity with time might be attributed to the increased of soil organic matter content with the application of NRTWC. The highest porosity change was observed at 1 % treatment (from 44.9% to 48.8%) and the lowest was at 2.8% (from 49.4% to 56.3%). Despite no significant (p ≥ 0.05) difference was reported in particle size distribution in soil treated with NRTWC, there was a noticeable decreased in sand percentage and increased in either silt or clay percentages at 20 weeks after application. Soil aggregate stability was found to be significantly increased (p ≤ 0.05) in all treatments at 10 and 20 weeks after NRTWC application compared to the control. However, further investigations are needed before recommending the addition of NRTWC as an amendment to tea growing soils.