Abstract:

To investigate the uptake and utilization of nitrogen and its residual and loss in the soil of ‘Huangguan’pear trees during the no-bearing stage to the young bearing stage,the growth of various organs and the uptake,residual and loss of labeled nitrogen at 0-100 cm soil layers were studied during the years of 2014-2016 with ¹⁵N tracer technique. The results showed that the growth of pear trees in the no-bearing stage（2014-2015）mainly displayed in the growth of the central trunk and coarse root with a lower growth rate. However,it showed that the establishment of tree structure,the growth of vegetative organs such as branches and shoots,and the formation of yield and quality coexisted in the young bearing stage. During the whole experiment period,the amount of labeled nitrogen absorbed by the storage organs of the tree was larger,among which absorption of the central trunk’s uptake was the largest in the no-bearing stage,while the amount of labeled nitrogen absorbed by the coarse roots was the largest among all tested organs in the young bearing stage. After the application of labeled nitrogen in the first year （2014）,the utilization rate of labeled nitrogen was 3.25% for the pear trees,while the residual rate of labeled nitrogen in 0-100 cm soil layer was higher accounting for 63.61%. In the following two years （2015-2016）,the residual amount of soil was lower,and the utilization rate of labeled nitrogen for pear trees was only 0.51% and 0.80%. By the end of the experiment,the utilization rate and residual rate of labeled nitrogen was 4.57% and 20.34% respectively,however,the three-year loss rate was as high as 75.07%.

Key words: pear, no bearing stage, young bearing stage, ¹⁵N-urea, uptake, residual effect