The researchers studied how different combinations of common urea and slow-release urea affect the growth and nitrogen use of summer maize in Hebei Province. They found that a mix of 3 parts common urea to 7 parts slow-release urea resulted in the highest grain yield and nitrogen use efficiency. This combination led to more ears and grains per ear, as well as increased nitrogen uptake by plants. The varieties of maize tested also showed improved leaf area and photosynthetic rate after flowering, which helped with post-flowering growth. This research provides a basis for using slow-release urea in summer maize production in the region.