Effect of Biochar, Potting Mixture and their Blends to Improve Ocimum basilicum Growth in Sandy Soil

Biochar has received significant interest as a soil amendment but its relative performance to addition of high-quality soil is not well assessed. This study compared different loadings of cabbage-waste biochar produced at 360 degree celsius against potting mixture (PM) as amendments to enhance basil (Ocimum basilicum) growth in sandy soil. Pot tests for six conditions of biochar, PM or their blend were tested at both 2% or 6% loading, plus a control, with soil and plant characteristics monitored. The combination of 6% biochar and 6% PM increased seed germination by 85% compared to the control, while 6% biochar applied in sandy soil reduced seed germination by 29%. However, significant benefits were realized later in the growing stage in comparison to the control and most other tested conditions. The 6% application of biochar to the soil enhanced leaf chlorophyll and carotenoid contents, membrane stability index, and leaf relative water content by 198%, 150%, 15%, and 5% over the control, respectively. The highest shoot and total biomass were achieved with the combined application of 6% biochar and PM, followed by 6% biochar only. When comparing only application of biochar or PM, biochar was the more favorable soil amendment at both 2% and 6% loadings. Biochar was also effective at enhancing plant uptake of beneficial nutrients, while immobilizing Al, which is detrimental, in the soil. Overall, biochar is a better soil amendment for sandy soil than equivalent quantities of PM, but mild benefits occur through their combined application.