N Utilization, Residual and Loss Characteristics of Spring-Topdressing (15N-urea) Pear Orchards in the Old Course of the Yellow River Area

In the old course of Yellow River area, most orchards are over-applied with nitrogen (N) fertilizers. To improve N management in this a 15N tracing experiment was conducted to investigate absorption, distribution and loss spring-topdressing urea pear from March August 2019. The 7-year-old Sucui 1 used as test material, 277.5 g ordinary 15 15N-urea were evenly applied each plant. utilization efficiency different organs flowering stage post-harvest analyzed, residual soil also discussed. fertilizer rate increased advancement phenological period. full bloom period is 10.39%, which fastest growing period, reached maximum 23.62% stage. young fruit stage, amount derived labeled (%Ndff) only 1.02%, new vegetative above 1%. Residual 20–40 cm layer significantly higher than that other layers. Direction loss>soil residue>tree absorption. expansion harvest higher, 3.76 3.74 g, respectively. area low throughout year. There nutrient competition between reproductive growth growth, can be effectively alleviated by spring top-dressing. during harvesting serious. Attention should paid split application timely supplementation an appropriate use efficiency.