不同施氮量对水稻氮素吸收与分配的影响

运用15N示踪法研究了不同施氮量对两个品种水稻（4007和武运粳15）干物质积累量与其对15N吸收及分配的影响。结果表明，当施氮量超过N 150 kg/hm2时, 两个品种水稻子粒产量均不再显著增加。4007在4个施氮量下(N 100，150，200和 250 kg/hm2)分别比无氮区增产22.3%，36.9%，43.2%和38.1%；武运粳15分别增产10.6%，18.8%，27.1%和21.5%。同一施氮量下，4007子粒中15N累积量显著高于武运粳15，但茎叶和根中没有差异。增加施氮量降低了15N在水稻子粒中的分配比例，但提高了茎叶中15N的分配比例。15N在根中的分配比例不受施氮量和品种的影响。研究结果还表明，同一施氮量下，4007对肥料氮的总体利用率要比武运粳15高3～6个百分点。

Effect of nitrogen application rate on nitrogen uptake and distribution in rice

A micro-plot experiment using ¹⁵N labeled fertilizer was conducted to compare the effects of different nitrogen application rates on dry matter production, ¹⁵N uptake and distribution in two different rice cultivars, 4007 and Wuyunjing15 (WYJ15). The results obtained are listed as follows. There were no significant increments in yield of both rice cultivars if the nitrogen application rates were over N 150 kg/hm², and the percentages of rice grain yield increase over control were 22.3%, 36.9%,43.2% and 38.1% for 4007 at N application rates of N 100, 150, 200 and 250 kg/hm², respectively; while they were only 10.6%, 18.8%, 27.1% and 21.5% for Wuyunjing15. The ¹⁵N accumulation in grains of 4007 was much higher than in Wuyunjing15，but there were no significant differences in straws and roots between the two cultivars under the same nitrogen application rate. The ¹⁵N distribution in grains increased significantly with nitrogen application rates, but there was a reverse trend in straws, and no difference in roots of these two cultivars among N application rates. The study also showed that, at the same N application level, the total nitrogen utilization coefficient in 4007 was 3%–6% higher than in Wuyunjing15.