Optimizing water and nitrogen supply can regulate the dynamics of dry matter accumulation in maize, thereby promoting dry matter accumulation and increasing yield

Dry Matter Accumulation (DMA) is a critical factor in yield formation. Investigating the effects of irrigation and nitrogen application on the DMA and yield formation in maize is essential to provide a theoretical basis for regulating yield formation. Over the course of two years (2022–2023), field experiments was conducted in Karamay, Xinjiang, China, with three irrigation levels (75 % ET_c, 100 % ET_c, 125 % ET_c) and four nitrogen application rates (0 kg N/ha, 93 kg N/ha, 186 kg N/ha, 279 kg N/ha). The study analyzed the effects of water and nitrogen levels on maize DMA and yield. Additionally, the Richards model for maize DMA under different water and nitrogen levels was established based on relative effective accumulated temperature. The model's parameters were used to quantitatively analyze the dynamics of DMA and its grain yield effects. The results indicate that the optimal combination of irrigation and nitrogen application for the study area is 100 % ET_c irrigation and 186 kg/ha of nitrogen. The maximum dry matter accumulation over two years was 32756 kg/ha and 33750 kg/ha, while the maximum yields were 19650 kg/ha and 18576 kg/ha, respectively. The Richards model, based on relative effective accumulated temperature for DMA, demonstrates the significant biological relevance with a determination coefficient (R²) exceeding 0.99 and an NRMSE (Normalized Root Mean Square Error) less than 10 %. At the irrigation level of 100 % ET_c and nitrogen application rate of 186 kg/ha, maize exhibited the highest average rate of DMA, entering the rapid growth phase earlier and sustaining it for a longer duration. Y₂ (DMA during the rapid growth phase) and Y₃ (DMA during the slow growth phase) were significantly positively correlated with yield (P ≤ 0.05), with correlation coefficients of 0.71 and 0.57, respectively. Additionally, hundred-grain weight and grain number per ear showed a significant positive correlation with both Y₂ and Y₃ (P ≤ 0.05), with correlation coefficients of 0.68, 0.59, and 0.76, 0.58, respectively. Therefore, optimizing water and nitrogen supply can regulate dry matter accumulation during the rapid and slow growth phases, promoting maize dry matter accumulation and, in turn, enhancing yield. The findings of this study provide a theoretical reference for water-nitrogen management, as well as dry matter and yield regulation, in the study area or other regions with similar climatic conditions.