Localized fertilizer co-applied with biochar suspension increases phosphorus uptake by maize

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, ³³P-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. ³³P-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. ³³P-imaging revealed higher activity of ³³P 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.