Influence of biochar derived from agricultural waste on soil properties and productivity of carrots (Daucus carota)

Biochar derived from agricultural waste has attracted considerable attention as a sustainable soil amendment, yet comparative evidence on feedstock-specific effects in root vegetable systems remains limited. This study evaluated the effects of biochar produced from corn cobs, coconut husks, peanut shells, and sugarcane bagasse on soil chemical properties, growth, and productivity of carrot (Daucus carota L.) under field conditions. The experiment was conducted from October 2022 to February 2023 using a randomized complete block design with five treatments, including an unamended control, and three replications. Biochar application significantly increased soil pH (from 5.62 in the control to 6.05–6.41), soil organic carbon (from 1.21% to 1.61–1.89%), and available nitrogen (from 48.3 to 61.8–71.6 mg kg⁻¹) relative to the control. Improved soil conditions translated into enhanced carrot growth, with plant height increasing from 42.3 cm in the control to 53.7 cm under corn cob biochar, and root diameter increasing from 3.12 to 4.41 cm. All biochar treatments significantly improved total and marketable yields compared with the control. The highest total yield was obtained with corn cob biochar (23.1 t ha⁻¹), representing an approximately 25% increase over the control (18.4 t ha⁻¹), while marketable yield increased from 15.6 to 20.2 t ha⁻¹. Biochar application also improved root uniformity and visual quality. Overall, the results demonstrate that agricultural-waste-derived biochar, particularly corn cob biochar, enhances soil fertility and carrot productivity and represents a viable, environmentally sustainable alternative to conventional soil fertility management.