为研究大豆(Glycine max)叶面适宜施氮量及叶面氮素吸收与利用的规律, 以黑龙江省三江平原大豆主栽品种合农64为实验材料, 采用¹⁵N标记示踪法在大豆需氮关键时期R₅期进行叶面施氮, 分析大豆组织器官标记氮素的积累量及回收率。结果表明: 在4.5 kg·hm^-2 (N3)施氮条件下, 大豆组织器官干物质量及氮素积累量显著高于其它处理, 其中籽粒干物质平均重22.7 g, 总干物质平均重73.2 g, 分别比不施氮处理(N0)高17.92%和16.38%; 籽粒氮素积累量平均为134.4 mg∙plant^-1, 比不施氮处理(N0)高13.13%, 说明4.5 kg·hm^-2 (N3)施氮条件是合农64在R₅期的最适叶面施氮量。在不同施氮条件下, 各组织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, 籽粒标记氮积累量在4.5 kg·hm^-2 (N3)施氮条件下最高, 为9.96 mg∙plant^-1。这一结果同样说明了4.5 kg·hm^-2 (N3)是合农64在R₅期的最适叶面施氮量, 同时明确了叶面氮素是籽粒氮素积累增加的主要原因。在同一施氮水平下, 各组织器官标记¹⁵N积累量顺序为籽粒>茎>叶>荚皮>叶柄>根, 且各器官间差异显著, 说明在R₅期叶面施氮籽粒积累的叶面氮素最多。从¹⁵N标记在各组织器官的贡献率来看, 在3.5 kg·hm^-2 (N1)施氮条件下, 籽粒氮素贡献率与植株氮素回收率最高, 说明在叶面施氮量较小的条件下, 氮素更容易被籽粒吸收利用, 但净积累量却低于最适施氮量处理(N3)。在3.5 kg·hm^-2 (N1)施氮条件下, 植株氮素回收率高于最适施氮量处理(N3)。

To study nitrogen application and utilization rates in soybean leaves, we used the major soybean cultivar in the Sanjiang Plain of Heilongjiang province HeNong64 to analyze nitrogen accumulation and recovery rate in soybean leaves of the R₅ stage with the ¹⁵N tracing technique. Dry weight and nitrogen accumulation of soybean organs were significantly higher with 4.5 kg∙hm^-2 than other treatments. The dry weight of seeds was 22.7 g and the total plant dry weight was 73.2 g, which were significantly higher than without nitrogen application, by 17.92% and 16.38%, respectively. The nitrogen accumulation in seeds was 134.4 mg per plant and higher than without nitrogen application by 13.13%, so 4.5 kg∙hm^-2 was the most suitable leaf nitrogen application amount for HeNong64 in the R₅ stage. Under the tested nitrogen levels, ¹⁵N accumulation in different organs first increased then decreased with increasing nitrogen levels, and the ¹⁵N accumulation in seeds was the highest (9.96 mg per plant) with 4.5 kg∙hm^-2 treatment. Therefore, 4.5 kg∙hm^-2 was the most suitable leaf nitrogen application amount for HeNong64 and leaf nitrogen was the main source of nitrogen for seeds. Under the same nitrogen application level, ¹⁵N accumulation in different organs was in the order of seed>stem>leaf>pod> petiole>root and the nitrogen accumulation was significantly higher in seeds than in other organs in the R₅ stage. The ¹⁵N contribution rate and plant nitrogen recovery rate in seeds with 3.5 kg∙hm^-2 was highest, so nitrogen was easier to be absorbed with lower leaf nitrogen application, but its net accumulation was lower than 4.5 kg∙hm^-2 and the plant nitrogen recovery rate was higher than 4.5 kg∙hm^-2.