Fertilizer and soil nitrogen utilization of pear trees as affected by the timing of split fertilizer application in rain-fed orchard

Split fertilizer application has been proven to improve nitrogen utilization efficiency in field crops. A N-15 tracing experiment was conducted to investigate the effects of nitrogen application timing on the fertilizer and soil nitrogen uptake of rain-fed pear trees from October in 2014 to October in 2016. Treatments included: 1) control, fertilized only once in autumn; 2) T1 fertilized once in autumn and once after petal fall in next season; and 3) T2, fertilized once in autumn and twice after petal fall in next season. The results showed that split fertilizer application improved the dry weight, nitrogen uptake of pear trees, reduced the fertilizer nitrogen loss and increased the residual fertilizer nitrogen in the soil as measured in mid-September. Once fertilizer application after penal fall decreased fertilizer nitrogen utilization, but it increased residual fertilizer nitrogen compared with twice application. This more residual fertilizer nitrogen could be absorbed during the autumn and remobilized in the spring. The uptake of soil nitrogen was promoted by the split fertilizer application, but no significant difference in soil nitrogen uptake was noted between T1 and T2, and this may be attributed to the slow soil organic matter mineralization during the dry and hot growth seasons. The split fertilizer application improved nitrogen utilization efficiency of the pear trees and fertilization only once after the petal fall (T1) saved labor costs in rain fed pear orchard.