Effect of charcoal-blended compost on plant growth of Brassica rapa var. peruviridis for reduction of nitrogen fertilizer use

Agricultural use of biochar has recently been paid attention as an alternative strategy for mitigating greenhouse gas emissions and as a useful tool for enhancing soil fertility. Our study focused on the effects of compost with biochar on plant growth and soil properties to address whether poultry manure compost with or without biochar (PM, PM+B) as an additional component of compost is an alternative for the replacement of chemical nitrogen fertilizer. A treatment with a sole chemical fertilizer was set up as a control in a plant growth experiment using komatsuna (Brassica rapa var. peruviridis). Based on calculation of the same nitrogen content as the control (0% organic fertilizer), four different doses (12.5, 25, 50, and 100%) of compost with and without biochar (PM, PM+B) were tested for the replacement of a chemical N fertilizer (urea). After the experiment, morphological measurements, nutrient content in the leaf, and soil physico-chemical properties were analyzed. Root fresh weight and root activity in the treatment with PM+B (25 and 50%) was much higher than in the control (100% chemical N fertilizer), although no differences were observed in shoot weight or plant height. Vitamin C content in the leaf was higher after the application of PM and PM+B than in the control. Concerning soil characteristics, the combination between chemical fertilizer and PM+B (25 and 50%) increased both total and water-soluble carbon content. Synergic effect of chemical and organic fertilizer application gave favorable results in providing equilibrate nutrient components in a leafy vegetable and mitigated the environmental risk in soil.