Optimizing Soil Properties and Root Morphology with Biochar and Nitrogen Fertilization Enhances Maize Resource-Use Efficiency in a Semi-Arid Cropping System

Biochar is one of the effective practices to enhance agricultural productivity in semi-arid regions. In this study, a field experiment with three biochar application rates and three nitrogen fertilizer levels was conducted in the northwestern region of China.Investigating the regulatory role of biochar in modulating physiological processes at the maize root-soil interface and its influence on nutrient uptake and utilization. The results indicated that applying biochar together with nitrogen fertilizer significantly increased soil organic carbon (12.1%–18.2%) and soil total nitrogen (39.0%–45.0%). Meanwhile, the ratio of soil organic carbon to soil total nitrogen decreased by 18.5%–19.3%, suggesting a more coordinated soil carbon and nitrogen supply. The combined application of biochar and nitrogen fertilizer significantly improved maize root traits, with root biomass, root length, root surface area and root volume increasing by 112.0%–116.5%, 53.4%–62.7%, 176.5%–187.0% and 142.9%–147.8%, respectively. Meanwhile, the dry matter accumulation of maize was enhanced by 6.25%–7.33%, and the grain yield was elevated by 17.9%–20.8%, while the nitrogen use efficiency was stably maintained at 60%.The combined application of biochar (5000 kg·ha ^-1 ) and medium-dose nitrogen fertilizer (240 kg·ha ^-1 ) not only enhances corn production but also improves the efficient utilization of nitrogen fertilizer by simultaneously increasing soil carbon and nitrogen storage capacity, as well as promoting root growth and dry matter accumulation.