This study investigates the impact of various water supply modes on the hydraulic reliability of large-scale irrigation networks. An EPANET hydraulic model was developed to simulate the performance of the irrigation network under three supply modes: segmented, uniform, and random water supply. Three key indicators were selected to evaluate the hydraulic reliability of the pipeline network under each mode: Water Supply Uniformity C_u, Pressure Reliability H_k, and Velocity Reliability $\left|v\right|$. These parameters were standardized using the min-max normalization method, and the resulting reliability scores were scaled to a unified range of 0–5, where higher values indicate greater system reliability. The results demonstrate that the EPANET model effectively simulates the hydraulic performance of large-scale irrigation networks. Specifically, under the segmented water supply mode, the reliability values for water supply uniformity, node pressure head, and flow velocity are 4.04, 0.84, and 0.64, respectively. Under this mode, significant flow deviations and pressure head fluctuations occur between the branches, with flow velocities typically exceeding the optimal range. Furthermore, the node pressure head at the branch inlets fails to meet the required minimum pressure head (H_min), indicating potential operational inefficiencies. In the uniform water supply mode, the highest reliability values are observed for water supply uniformity (4.76) and flow rate (4.49), with node pressure head reliability (0.94) slightly surpassing that of the segmented mode. Pressure head fluctuations and flow deviations are significantly reduced, with flow velocities generally aligning with the economic flow rates of the pipeline. However, despite these improvements, many nodes still fail to meet the required minimum pressure head, indicating limitations in meeting demand under peak conditions. In the random water supply mode, node pressure head reliability reaches its highest value (1.54), while water supply uniformity and flow rate reliabilities are 3.99 and 2.50, respectively. Flow deviations and pressure head fluctuations are comparable to those observed in the uniform supply mode. Notably, a higher proportion of nodes meet the minimum pressure head requirement compared to the uniform mode. Overall, the hydraulic reliability of the pipeline network is highest under the uniform water supply mode (2.83), followed by the random water supply mode (2.49), with the segmented water supply mode exhibiting the lowest hydraulic reliability (1.79). These findings provide valuable insights for the selection of optimal water supply modes and the assessment of hydraulic reliability in large-scale irrigation systems.

To investigate the effect of nitrogen application and soil microbial activity on the decomposition process of stalk material in stalk composite pipes (SCPs) under subsurface irrigation with stalk composite pipes (SSI), in this study, a field experiment was conducted with two fertilization strategies—banding fertilization and SCP fertigation—at three nitrogen doses (126, 168, and 210 kg/ha), and the Biolog Ecoplate™ was employed to determine soil microbial activity. The results showed that under banding fertilization, the soil microbial activity at 20 cm subsoil and at the SCP wall increased with the increase in nitrogen dosage, ranging from 37.6% to 54.3% and from 21.5% to 23.7%, respectively. Under SCP fertigation, the soil microbial activity at 20 cm subsoil first showed a 58% surge, followed by a 3.9% decrease, with no significant variation in soil microbial activity at the SCP wall. Forty-five days later, the crude fiber content in the SCP wall under SCP fertigation was 17.6–26.3% lower than that under banding fertilization. Based on the comprehensive analysis of the soil microbial activity, SCP fertigation combined with high nitrogen application can accelerate the decay rate of straw in SCPs. This research can provide a reference for formulating irrigation and fertilization regimes for SSI.