Fertilizer Value of Nutrient-Enriched Biochar and Response of Canola Crop

Excessive use of chemical fertilizers (CFs) can result in a decrease of soil organic matter, lowering soil fertility and agricultural productivity. Biochar application could be a promising approach to reduce these issues and increase soil fertility. In this study, the effects of nutrient-enriched biochar (NEBC) on soil properties and canola (Brassica napus L.) plant growth were investigated. A pot experiment was conducted following a completely randomized design with three replications. Two contrasting Australian soils were amended with three doses (i.e., control, 1%, and 5% w/w) of three NEBCs, one biosolid biochar (BSBC), and CF. The canola plant growth experiment spanned over eight weeks assessing the effects of the amendments. Soil properties were examined after plant harvesting. NEBC and BSBC lowered soil pH (up to 1.38 units) and increased soil EC (up to 378 µS cm⁻¹). They also increased P (up to 19-fold) and K (up to 0.67 g kg⁻¹) availability, improving canola growth compared to CF. Biochar increased dehydrogenase enzyme activity (up to twofold), but NEBC reduced seed germination due to high nutrient content. Nutrient concentration in plant tissues increased with NEBC and BSBC application. Application of NEBC and BSBC improved soil properties, resulting in increased growth of canola. The application rate of NEBC fertilizer requires further optimization to improve soil fertility and crop productivity.