氮肥施用期对苹果幼树吸收、贮藏和再利用~(15)N的影响

以~(15)N标记的硫酸銨作示踪剂,研究了田间栽植的苹果幼树对春、夏、秋和分期施用氮肥的吸收利用规律。春季吸收的~(15)N数量很少,但进入体內者能迅速运送到地上部新生器官,根内存留很少,初夏所施~(15)N能在短期內被根系大量吸收,并较均衡地分配于多数器官;秋施~(15)N处理一个月后树体内~(15)N含量较春施者高,且此时吸收的~(15)N主要贮于根和主干中。春、夏施增加~(15)N贮备水平的作用较小,秋施能显著提高贮藏~(15)N含量,且于翌春能最大限度地把贮藏~(15)N调运到新生器官;分期施氮不仅影响当年的生长发育,还显著提高了贮藏~(15)N水平。

EFFECTS OF NITROGEN APPLICATION TIME ON ~(15)N ABSORPTION, STORAGE AND REUTILIZATION IN YOUNG APPLE TREES

The present study was carried out during 1984-1985 at ShandongAgricultural University. The effects of nitrogen application time onnitrogen uptake, storage and reutilization in young apple trees (cv.Rails Spur grafted on M. prunifolia Borkh. ) grown in the field werestudied, using ~(15)N-labelled ammonium sulphate as a tracer. The resultshowed that the uptake of ~(15)N was much lower in the trees receivingspring fertilization in one month after the application. The ~(15)N absorbedduring that time was transported to the new growth of above groundparts rapidly, and the amount of ~(15)N remained in the roots was verylittle. Following the application of ~(15)N in the early summer, the treesabsorbed a large amount of ~(15)N in a short period and this ~(15)N wasdistributed more evenly to different organs. During one month followingapplication, the amount of ~(15)N absorbed by autumn-fertilized trees was alittle more than that by spring-fertilized trees. The ~(15)N absorbed duringautumn was stored mostly in the roots and leader. It was demonstrated that the level of ~(15) N reserves in the treesreceiving spring or summer fertilization was increased less than that inother treatments. A marked increase of ~(15)N reserves was detected inautumn-fertilized trees and the reserves were reutilized fully by the newgrowth during following spring. If ~(15)N was applied evenly in spring, summer and autumn with the same total amount as in other treatments,not only the current growth of the trees would be affected, but the levelof ~(15)N reserves would be markedly higher than that in spring- orsummer-fertilized trees, just a little lower than that in autumn-fertilizedtrees.