小麦 玉米轮作区西农979不同器官氮素转运及对籽粒贡献率的影响

为了解华北地区小麦玉米轮作模式下小麦不同器官氮素吸收、分配及转运的差异，采用田间试验方法，以西农979为供试品种，于小麦的分蘖期、越冬期、返青期、拔节期、抽穗期、灌浆期和成熟期采集植株样品，对其叶、叶鞘、茎、穗轴、颖壳和籽粒的干物重及氮含量进行了测定和分析。结果表明，小麦成熟时，不同器官氮含量从大到小依次为：籽粒＞叶＞叶鞘＞颖壳＞茎＞穗轴，氮积累量从大到小依次为：籽粒>叶鞘>叶>茎>颖壳>穗轴，即氮在籽粒中分配和积累量最大，叶是最大的氮素“源器官”。在不同生育阶段，拔节至抽穗期的氮吸收量和吸收速率最大。在华北小麦玉米轮作区，籽粒氮收获指数达到68.48%，而叶对籽粒的氮转运贡献率达到54.52%；拔节至抽穗期氮素吸收比例占全生育期的48.07%，故而底施氮肥与拔节期追氮的比例控制在5∶5为好。

Nitrogen Translocation and Conversion Rate to Grain of Xinong 979 in Wheat corn Rotation Area

In wheat corn rotation area of northern China plain, regulations of the uptake, distribution and translocation of nitrogen in different organs of wheat at different growth stages were studied, and differences of nitrogen translocation conversion rate to grain of different vegetative organs of wheat were analysed. In field experiment with Xinong 979 as material, samples of wheat were obtained at different growth stages, such as tillering, wintering, regreening, jointing, heading, grainfilling and maturing stages. Then, different above ground organs, including leaf, leaf sheath, stem, spike, spike stalk, glume and grain, were separated, and their nitrogen contents were determined. At mature stage of wheat, the order of the nitrogen content in different organs of wheat was as grain > leaf > leaf sheath > glume > stem > spike stalk; and the order of the nitrogen accumulation in different organs of wheat was as grain > leaf sheath > leaf > stem > glume > spike stalk. The results suggested that grain was the biggest organ of nitrogen distribution and accumulation in wheat, and leaf was the biggest source organ of nitrogen. Additionally, the growth stage from jointing to heading of wheat was the biggest uptake stage of nitrogen. In wheat corn rotation area of northern China plain, nitrogen harvest index of grain was 68.48%; nitrogen translocation conversion rate to grain from leaf was 54.52%; the uptake rate of wheat from jointing to heading stage was 48.07% of that in all growth periods. So the basal/topdressing ratio of nitrogen fertilizer should be five to five.