Apple (Malus domestica) is an economically important fruit tree that is extensively planted worldwide. Nitrogen is the most important nutrient for crop productivity; effective nitrogen utilization is the key to high plant yields in agricultural production, but full absorption of soil nitrogen by plants can be a challenge. Nutrient absorption and utilization are very important for apple growth, and a lack of sufficient nitrogen can affect flowering time, yield, and fruit quality. Therefore, research aimed at increasing nitrogen absorption efficiency is important for apple quality improvement.