Soil moisture and nutrient mobility influence nitrogen partitioning and translocation in maize (Zea mays L.) under various water-nitrogen regimes

Optimizing water and nitrogen (N) management is crucial for improving crop yields, yet the soil water dynamics and nutrient mobility on N partitioning and yield information remain insufficiently understood. To address this gap, field experiments were conducted from 2020 to 2022 in the western Songnen plain (SARs), a cold semi-arid region of northern China. The study examined three soil moisture levels (40 %, 60 %, and 80 % of field capacity) and four N fertilization rates (0, 100, 200, and 300 kg N ha −1 ) to evaluate their impacts on soil nutrient dynamics (SNs), soil water utilization (SWU), soil enzyme activities (SEAs), N accumulation (NA), N translocation (NT), N utilization (NU), biomass accumulation (BA), and maize yield. Results showed that maintaining soil moisture at 80 % field capacity (W3) significantly enhanced SWU and partitioning, particularly under the N200 treatment. Specifically, W3-N200 increased SWU by 4.15–26.13 %, SNs by 5.06–35.49 %, and SEAs by 6.57–38.78 % compared with W1 (40 %) and W2 (60 %). Regression analysis indicated that W3 advanced the time to peak BA rate by 11.76–17.85 days and increased maximum biomass (by 2.93–4.16 MG ha −1 ), peak BA rate (by 0.09–0.18 MG ha −1 d −1 ), and average BA rate (by 0.04–0.06 MG ha −1 d −1 ). Under N200, structural equation modeling (SEM) revealed increases in NA (13.95–34.65 %), NT and NU (3.14–27.49 %), resulting in a 4.99–28.81 % higher BA and 4.44–10.73 % greater yield. The W3-N200 treatment achieved the highest grain yield (10437 kg ha −1 ), with superior water use efficiency (38.09 %) and N use efficiency (NUE; 40.38 %). Optimal water and N management regulated SNs and SEAs, which in turn improved N transformation and BA, ultimately increased maize yield. These findings provide valuable guidance for sustainable water and nutrient management in SARs agricultural regions. • Maximum water and nitrogen utilization efficiency were higher under the W3-N200 treatment. • W3 reduced the Tmax while enhancing growth parameters such as Wmax , Gmax , and Gmean . • Optimal water-N management regulated SNs and SEAs, and improved N transformation and BA. • W3-N200 increased soil nutrient availability and its transport to above-ground parts.