Biochar-blended urea enhances wheat yield by integrating fertilizer-nitrogen utilization and photosynthesis

Abstract

Excessive nitrogen (N) application poses environmental risks, making improved N use efficiency (NUE) critical for sustainable agriculture. Biochar-based fertilizers provide slow-release N, which can improve crop productivity and NUE. However, the physiological mechanisms linking N fate with plant performance remain poorly understood. Using 15N tracing, this study investigated the effects of biochar-blended urea fertilizer (BF) and conventional urea fertilizer (UF) on fertilizer-N uptake, photosynthetic performance, and grain yield of winter wheat grown in fluvo-aquic soil on the North China Plain under high-N and low-N application rates. Compared with UF, BF significantly increased wheat grain yield by 18% under the high-N rate and 30% under the low-N rate. BF also altered stomatal morphology and spatial distribution in wheat leaves, thereby enhancing stomatal regulation of gas exchange and improving photosynthetic performance, as evidenced by increased net photosynthetic rate (An), transpiration rate (Tr), dark respiration rate (Ra), water use efficiency (WUE), stomatal conductance (Gs), maximum carboxylation rate (Vcmax), and maximum electron transport rate (Jmax), particularly under the low-N rate. In addition, BF significantly enhanced fertilizer-N uptake by 26.4%–40.0% and its translocation to the grain by 29.4%–34.0% compared with UF. Enhanced fertilizer-N uptake was positively associated with photosynthetic performance, and both jointly contributed to increased wheat grain yield. These findings demonstrate that biochar-blended urea enhances fertilizer-N use efficiency and photosynthetic performance, providing an effective strategy to reduce chemical N fertilizer inputs while sustaining wheat productivity. However, long-term field trials are needed to verify the effectiveness and agronomic benefits of biochar-blended urea under practical agricultural conditions.