The study looked at how different levels of irrigation and nitrogen application affect soil quality and maize yield in a subtropical region. They found that using 250 kg/ha of nitrogen fertilizer along with supplementary irrigation can increase soil fertility and maize yield. Specifically, this combination led to higher levels of soil nitrogen, organic carbon, and grain nitrogen content, resulting in a 22% increase in maize yield compared to rainfed conditions. Additionally, using 300 kg/ha of nitrogen fertilizer further increased yield and grain weight. Overall, the research suggests that proper irrigation and nitrogen application can improve soil health and crop productivity in double cropping maize systems.