The researchers conducted a field experiment to study how different amounts of nitrogen affect the yield and protein quality of two types of maize plants. They found that increasing nitrogen levels led to higher grain yield and protein content in both maize varieties. The maize plants performed best with 240 kg/ha of nitrogen. The study also showed that one of the maize varieties, Xianyu335, had higher grain yield and protein content compared to the other variety, Zhengdan958. Overall, the results suggest that using 240 kg/ha of nitrogen can help achieve a balance of high yield, quality, and efficient nitrogen use in maize cultivation.