The researchers studied different ways to reduce nitrogen fertilizer for growing tobacco. They found that reducing nitrogen fertilizer by 55% while applying 70% as top dressing can improve the soil's nitrogen supply for tobacco growth. When 70% of nitrogen was applied as basal or top dressing, tobacco absorbed nitrogen well even with reduced fertilizer. This led to better nitrogen use efficiency and agronomic efficiency without decreasing tobacco yield or quality. However, reducing fertilizer too much when applying 70% as top dressing can lower tobacco yield and quality. Overall, reducing fertilizer can effectively provide tobacco with the needed nitrogen for growth.