Root-zone fertilization improves crop yields and minimizes nitrogen loss in summer maize in China

It is urgently to minimize nitrogen (N) loss while simultaneously ensuring high yield for maize in China. A two-year field experiment was conducted to determine the effects of root-zone fertilization (RZF) and split-surface broadcasting (SSB) on grain yield, N use efficiency (NUE), and urea-¹⁵N fate under different N rates (135, 180 and 225 kg ha^-1). Results showed that RZF increased grain yield by 11.5%, and the N derived from fertilizer (Ndff%) by 13.1-19.6%, compared with SSB. The percentage of residual ¹⁵N in the 0-80 cm soil was 37.2-47.4% after harvest; most ¹⁵N (64.4-67.4%) was retained in the top 20 cm. RZF significantly increased the N apparent recovery efficiency (NARE) and ¹⁵N recovery in maize by 14.3-37.8% and 21.9-30.0%, respectively; while decreased N losses by 11.2-24.2%, compared with SSB. The RZF of urea can be considered a slow-release fertilizer, which better matches maize N demand and effectively reduces N losses. Overall, RZF achieved yields as high as the SSB, but with a 20-25% reduction in N application. These results help improve our understanding of N fate in the maize cropping system, and may help guide recommendations for N management in southeastern China.