The study looked at how different amounts of nitrogen fertilizer affected maize growth and soil nitrogen levels when straw was returned to the farmland. They found that maize yield increased with more nitrogen fertilizer, but only up to a certain point. Beyond that, the yield started to decrease. The best amount of nitrogen to use was 216 kg per hectare. Over two years, the efficiency of nitrogen use by the maize plants improved. However, there was a risk of nitrate pollution in the soil, especially in the top layers. To balance maize production, nitrogen use efficiency, and environmental benefits, the optimal nitrogen amount to use was 200 kg per hectare.