In order to improve the management of nitrogen(N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field...In order to improve the management of nitrogen(N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field experiment at Jingtai County, Gansu Province, China. Nine trees were selected for the experiment and each received equal aliquots of 83.33 g N in the autumn, spring, and summer, with ^(15)N-labeled(NH_4)_2SO_4 used in one of the aliquots each season. Results showed that the(^(15)NH_4)_2SO_4 applied in the autumn remained in the soil during the winter. In the following spring this N was absorbed and rapidly remobilized into each organ, especially new organs(leaves, fruit and new shoots). The ^(15)N supplied in spring was rapidly transported to developing fruit between the young fruit and fruit enlargement stages. ^(15)N from the summer application of fertilizer was mainly stored in the coarse roots over the winter, then was mobilized to support growth of new organs in spring. In conclusion, for pear trees we recommend that the autumn application of N-fertilizer be soon after fruit harvest in order to increase N stores in fine roots. Spring application should be between full bloom and the young fruit stages to meet the high N demands of developing fruit. Summer application of fertilizer at the fruit enlargement stage does not contemporaneously affect the growth of pears, but increases the N stored in coarse roots, and in turn the amount available for remobilization in spring.展开更多
Na clusters containing 10 to less than 1000 metal sodium atoms and blisters containing xenon inclusions were formed in NaCl crystal specimens prepared by xenon ion implantation to single crystal NaCl with Auences more...Na clusters containing 10 to less than 1000 metal sodium atoms and blisters containing xenon inclusions were formed in NaCl crystal specimens prepared by xenon ion implantation to single crystal NaCl with Auences more than or equal to 2×10^(16)/cm^(2)at the energy of 36keV.Experiments indicated that on the condition of xenon ion Auences more than or equal to 1×10^(17)/cm^(2)the xenon inside the inclusions formed in NaCl crystal specimens is in solid state and the solid state molecules NaXe are formed through the Combination of Xe with Na in Na clusters.The chemical shift of ^(23)Na in solid state molecules NaXe relative to 23Na in single crystal NaCl was measured and is equal to-17ppm.展开更多
基金funded by the earmarked fund of China Agriculture Research System(CARS-29-10)。
文摘In order to improve the management of nitrogen(N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field experiment at Jingtai County, Gansu Province, China. Nine trees were selected for the experiment and each received equal aliquots of 83.33 g N in the autumn, spring, and summer, with ^(15)N-labeled(NH_4)_2SO_4 used in one of the aliquots each season. Results showed that the(^(15)NH_4)_2SO_4 applied in the autumn remained in the soil during the winter. In the following spring this N was absorbed and rapidly remobilized into each organ, especially new organs(leaves, fruit and new shoots). The ^(15)N supplied in spring was rapidly transported to developing fruit between the young fruit and fruit enlargement stages. ^(15)N from the summer application of fertilizer was mainly stored in the coarse roots over the winter, then was mobilized to support growth of new organs in spring. In conclusion, for pear trees we recommend that the autumn application of N-fertilizer be soon after fruit harvest in order to increase N stores in fine roots. Spring application should be between full bloom and the young fruit stages to meet the high N demands of developing fruit. Summer application of fertilizer at the fruit enlargement stage does not contemporaneously affect the growth of pears, but increases the N stored in coarse roots, and in turn the amount available for remobilization in spring.
基金the Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Chinese Academy of Science under Contract 971503the Educational Foundation of Civil Aviation Administration of China under Contract 97-3-040.
文摘Na clusters containing 10 to less than 1000 metal sodium atoms and blisters containing xenon inclusions were formed in NaCl crystal specimens prepared by xenon ion implantation to single crystal NaCl with Auences more than or equal to 2×10^(16)/cm^(2)at the energy of 36keV.Experiments indicated that on the condition of xenon ion Auences more than or equal to 1×10^(17)/cm^(2)the xenon inside the inclusions formed in NaCl crystal specimens is in solid state and the solid state molecules NaXe are formed through the Combination of Xe with Na in Na clusters.The chemical shift of ^(23)Na in solid state molecules NaXe relative to 23Na in single crystal NaCl was measured and is equal to-17ppm.
