【目的】叶面喷施氮肥在大豆生产中已普遍应用，大量研究报道表明叶面喷施氮肥能够使大豆获得不同程度的增产。本研究在前人研究的基础上，采用15 N示踪技术，探索不同施氮量下氮素经大豆叶面吸收后在大豆植株各组织器官的积累与分配情况，为大豆叶面氮肥的高效利用提供理论依据。【方法】在黑龙江省大豆优势产区三江平原，以该地区5年内推广种植面积最大的大豆主栽品种“合丰55”为试验材料，采用15 N示踪技术，以上海化工研究院生产的丰度为20．17%的15 N标记尿素水溶液为叶面肥料，设置不同叶面氮素喷施量处理N 0、3．5、4．0、4．5、5．0 kg/hm2(N0、N1、N2、N3、N4)，在大豆重要的需氮时期鼓粒期(R5)进行叶面施氮处理。分析不同叶面氮素喷施量对大豆标记氮吸收、分配利用规律以及对产量的影响。【结果】叶面喷施N 4．5 kg/hm2( N3)大豆各器官干物质积累量、氮素含量及氮素积累量均显著高于其他处理(P<0．05)。与不施氮处理(N0)相比，籽粒干重(21．7 g/plant)和总干物重(70．1 g/plant)分别增加6．37%和8．51%，籽粒氮素含量(6．15 g/kg)增加10．81%，籽粒氮素积累量(133．3 mg/plant)增加18．07%。在同一施氮水平下，大豆不同器官标记N积累量为籽粒>茎>叶>荚皮>叶柄>根，差异达到显著水平( P<0．05)。在施氮量为4．5 kg/hm2处理条件下，籽粒标记氮积累量(9．76 mg/plant)分别较茎(2．46 mg/plant)、叶(1．28 mg/plant)、荚皮(1．26 mg/plant)、叶柄(0．9 mg/plant)及根(0．41 mg/plant)高2．96、6．63、6．75、9．84和22．8倍。不同施氮处理下，各器官标记氮积累量随着施氮量的增加呈先增加后降低的趋势，在施氮量为4．5 kg/hm2处理条件下达到最高值，其中籽粒中标记氮达到9．76 mg/plant。标记氮在各器官的分配比例与积累量无明显相关性，可能是不同施氮量下各器官干物质积累量不同所致，总体表现为籽粒>茎>叶>荚皮>叶柄>根，在施氮量为5．0 kg/hm2条件下籽粒标记氮分配率最高，为63．81%。【结论】在叶面喷施氮4．5 kg/hm2条件下，籽粒标记氮积累量和干物重最高，分别为每株9．76 mg和21．7 g。就“合丰55”品种而言，叶面施氮量为4．5 kg/hm2最有利于籽粒氮素及干物质积累。大豆鼓粒期( R5)进行叶面施氮时，氮素主要积累于籽粒中，有利于籽粒干物质积累，最终获得增产。%[Objectives] Forlia nitrogen application has been reported to increase soybean yield in different degrees. 15 N tracer technique was used to explore the nitrogen accumulation and distribution in different soybean organs with different nitrogen application rate, which can supply theoretical foundation for soybean leaf nitrogen efficient utilization and practical application. [Methods]This research was carried out in the soybean advantage producing area of Sanjiang Plain of Heilongjiang Province, the widely cultivated cultivar ‘HeFeng55’ in the past five years was selected as test materials. The 15N tracer technique and the 15N urea water solution(20. 17%)were produced in Shanghai Chemical Research Institute. The nitrogen spray amounts were set as:0, 3. 5, 4. 0, 4. 5 and 5. 0 kg/hm2 , recordered as N0, N1, N2, N3 and N4. Nitrogen was sprayed at the important needful nitrogen R5 stage, and the 15 N absorption and distribution, and the yield were measured. [Results]The dry weights, nitrogen contents and accumulation in the soybean organs are significantly higher with N 4. 5 kg/hm2 treatment than with other treatments(P<0. 05). The seed dry weightd and total plant dry weight are 70. 1 and 21. 7 g in treatment of N 4. 5 kg/ hm2 , with a significant increase of 8. 51% and 6. 15% compared with N0; the seeds nitrogen content is 6. 15 g/kg with an increase of 10. 81%; the seeds nitrogen accumulation is 133. 3 mg/plant with an increase of 18. 07%. Under the same nitrogen application level, the 15 N accumulation in different organs is in order of seed >stem> leaf > pod > petiole > root, and the differences reach significance level ( P<0. 05 ) . The seed nitrogen accumulation in N 4. 5 kg/hm2 is 9. 76 mg/plant, those in the stems, leaves, pods, petioles and roots are 2. 46, 1. 28, 1. 26, 0. 9 and 0. 41 mg/plant. The N accumulation in seeds is 2. 96, 6. 63, 6. 75, 9. 84 and 22. 8 times higher than the above organs. Within the tested nitrogen levels, the 15 N accumulation is first increased then decreased with the increase of nitrogen levels, and the highest seed 15 N accumulation(9. 76 mg/plant) is achived in the N 4. 5 kg/hm2 treatment. The 15 N distribution ratios and accumulation in different organs are not related to their dry biomass. The distribution ratios in different organs are all in the order of seed >stem>leaf>pod> petiole>root, and the highest seed 15 N distribution ratio(63. 81%) is in the treatment of N 5. 0 kg/hm2 . [Conclusion]The highest seed 15 N accumulation and dry weights are achieved when the forlia application rate of N is 4. 5 kg/hm2 , which should be thought the most optimum amount for the cultivar ‘HeFeng55 ’ . The appropriate forlia spray time is at the R5 stage, during which period, more applied N will be accumulated in seeds and in favour of the seed dry weight accumulation, achieving higher yield at last.
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