Localized fertilizer co-applied with biochar suspension can increase phosphorus uptake by maize while enabling carbon-sequestration benefits

Abstract Background and aims Integrating biochar (BC) into agriculture promotes sustainable management of farm residues and carbon sequestration in soil. This study evaluates a novel approach combining suspended biochar with phosphorus (P) fertilizer to assess its effectiveness in promoting P nutrition during early maize ( Zea mays L . ) growth. Methods Biochar suspension (equivalent to 300 kg dry biochar ha −1 ) was mixed with liquid P fertilizer (30 kg P ha −1 , 33 P-labeled) and band-applied to maize in the rhizobox experiment. Five treatments—control without fertilizer, BC only, P fertilizer only, and combined BC + P with and without plants—aimed to assess the effect of biochar on soil P dynamics and plant P uptake. Results Our findings demonstrate that liquid P fertilizer can be effectively combined with biochar suspension without reducing P availability. After 38 days, up to 25% of fertilizer-P was recovered in the soil’s available P pool, regardless of BC presence. 33 P-imaging confirmed that P movement from the fertilizer band was not restricted by BC. Fertilizer increased plant P uptake, height, biomass, leaf area, root length and volume. Biochar significantly increased fertilizer-P recovery in plants from 14.9% to 17.6%, supporting nutrient cycling and fertilizer efficiency. 33 P-imaging revealed higher activity of 33 P in maize roots with BC + P co-application, though P redistribution patterns remained unchanged; plant roots showed neither preference nor suppression near biochar, even upon direct contact. Conclusion Localized co-application of biochar and P in suspension promotes maize growth during critical early stages and increases phosphorus use efficiency, supporting sustainable agriculture and a circular economy. Graphical Abstract