How to improve crop productivity by optimizing biochar application and irrigation schedule is critical for agricultural high yield, especially in northwest China. However, relevant conclusions vary by geographical and climatic zones, requiring massive field experiment to fully understand the mechanisms. Here, we selected a typical water-scarce and arid area in northwest China as the study area and conducted a two-year (2023-2024) field experiment on silage maize (Zea mays L, a main forage crop). We designed six treatment experiment that consisted of combinations of two irrigation regimes (full irrigation (FI) and deficit irrigation (DI)) and three biochar application rates (0 (T-B), 15 (M-B), and 30 (H-B) t ha(-1)). The results indicated that biochar application reduced soil compaction (SC) by 20.45%-46.49% in the silage maize root zone and decreased soil bulk density (SBD) by 2.84%-4.87%. Inter-annually, compared to the FI treatment, the DIMB (DI + 15 t ha(-1)) treatment significantly increased soil nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N), and soil organic matter (SOM) contents by 4.18%-9.41%, 15.35%-20.87%, and 40.67%-92.60%, respectively (P < 0.05). The interaction between irrigation and biochar application had a minimal effect on soil enzyme activities, while biochar application significantly enhanced the activities of urease, catalase, and sucrase (P < 0.05). Under the DIMB treatment, the silage maize aboveground biomass and grain yield were significantly increased by 7.55% and 18.71%, respectively (P < 0.05). Therefore, the combined application of deficit irrigation and 15 t ha(-1) biochar (DIMB) represents an effective management strategy for enhancing local soil fertility, improving the soil environment, and ultimately boosting silage maize aboveground biomass and grain yield. These results provide valuable references for the management of sustainable agricultural water use and biochar application in northwest China.