Biochar-based urea enhances nitrogen use efficiency and mitigates nitrogen leaching in greenhouse vegetable production

The sustainable development of greenhouse vegetable systems relies on enhancing nitrogen use efficiency (NUE) and minimizing nitrogen losses, especially leaching losses. Biochar-based fertilizers (BBFs) offer a promising solution to these challenges. This study addresses the research gap in biochar-based nitrogen fertilizers by developing granular biochar-based urea (BU), which integrates urea, biochar, and attapulgite for use in greenhouse vegetable production. 15 N isotope microlysimeter experiments were performed to compare the effects of BU and traditional urea on garland chrysanthemum yields, N leaching and 15 N recovery at different application rates (380, 310 and 190 mg N/kg soil). BU applciation significantly enhanced the fresh yield and dry matter content of garland chrysanthemum by 25.1 % and 22.8 %, respectively, compared to urea treatment. BU application also improved overall plant 15 N recovery by 94.6 %. However, plant 15 N recovery decreased as the N application rate increased. In the 0–0.4 m soil layer, the 15 N recovery of BU ranged from 31.1 % to 35.3 %, compared to 19.2–28.3 % for urea-N. High urea-N application reduced soil 15 N recovery, while BU increased it. BU application notably decreased inorganic N leaching and unaccounted 15 N losses by an average of 35.2 % and 76.0 % compared with urea treatment. At the same N application rate (380 mg N kg −1 ), the coapplication of biochar and urea reduced both plant and soil 15 N recovery and increased 15 N loss compared with those of BU application. This research highlights the potential of biochar-based urea fertilizers as a sustainable alternative to conventional chemical fertilizers in greenhouse production. • Biochar-based urea (BU) enhanced fresh yield of garland chrysanthemum. • Plant and soil 15 N recovery was significantly increased by BU. • BU reduced inorganic N leaching by 35.2 % on average compared to urea. • BU decreased inorganic N leaching from soil rather than from fertilizer.