Abstract: 【Objective】 To reveal the regularity of canopy light distribution and photosynthetic diurnal variation in continuous fixed-point quantitative nitrogen application cotton during boll period and its influence on yield.【Method】 Three fertilization treatments were carried out continuously without nitrogen application 0(N₀), continuous medium nitrogen 270 (N₂₇₀), continuous high nitrogen 450 (N₄₅₀) kg/hm² to analyze effects of continuous nitrogen application on cotton agronomic traits, canopy structure, canopy spatial distribution during flower-bell stage, diurnal variation of canopy during flower-bell stage, spatial distribution of cotton boll and yield.【Result】 Cotton plant height, fruit branch number, single boll weight and boll number per plant of continuous nitrogen application treatment were higher than those of non nitrogen treatment, and there were significant effects, but there was no significant difference between nitrogen application treatments. At 10:00-19:00 of flowering and boll stage, PAR interception rate of cotton canopy in different treatments was V-shaped with the center of row spacing as the valley bottom. When the PAR interception rates of cotton population were 0.75-0.9, the light distribution sites of no nitrogen treatment were at the height of 1-4 fruit branches, and the PAR transmittance was still 0.25-0.1, and N₄₅₀ treatment was located above the height of 7 fruit branches, so that the light resources under the 7 fruit branches were little, resulting in serious boll dropping; the PAR light interception of N₂₇₀ treatment at 7 fruit branches and above was still 0.5-0.9, and in the first fruit branch at 0.9-1, cotton population showed a good light environment. The diurnal variation of photosynthesis, transpiration rate (TR) and intercellular carbon dioxide concentration (CI) of cotton in flowering and boll stage were higher than those in non nitrogen treatment, but there was no significant difference among nitrogen application treatments, and stomatal limiting value (LS) was just the opposite. The results showed that the increase of nitrogen application could obviously slow down the phenomenon of midday depression of photosynthesis, but the degree of slowing down of photosynthetic midday depression of cotton with high nitrogen application rate decreased, and after reaching the second peak, the decreasing trend of net photosynthetic rate (PN) was almost consistent with that of N₂₇₀ treatment. Leaf water use efficiency (WUE) without nitrogen treatment after 16:00 decreased rapidly with time, and was gradually lower than that of nitrogen treatment. The highest yield of seed cotton in N₂₇₀ was 4 835.67 kg/hm², which was 7.25% and 5.44% higher than those of N₀ and N₄₅₀, respectively.【Conclusion】 Continuous nitrogen application at 270 kg/hm² can obtain better cotton population canopy structure, which is beneficial to the light distribution, improve the efficiency of light energy utilization and obtain higher yield.

Key words: cotton; nitrogen fertilizer; PAR interception rate; canopy structure; light distribution

摘要： 【目的】研究施氮棉花花铃期冠层光分布和光合日变化的规律及对产量的影响。【方法】连续2年定点定量设置3个施氮处理,分别为未施氮0(N₀)、中等施氮270(N₂₇₀)、高量施氮450(N₄₅₀)kg/hm²,研究定点定量施氮对棉花农艺性状、花铃期冠层光空间分布、花铃期冠层光合日变化、棉铃空间分布及产量的影响。【结果】连续施氮处理的棉花株高、果枝数、单铃重、单株成铃数相均高于未施氮处理,且存在显著性影响,但施氮处理间无显著性差异。花铃期10:00~19:00各个时段,不同处理棉花冠层PAR截获率均以行距中心为谷底呈现“V”字形。当棉花群体PAR截获率均为0.75~0.9时,未施氮处理的光分布位点在1~4果枝所处的高度,PAR透射率依然有0.25~0.1,N₄₅₀处理位于7果枝以上的高度,7果枝以下部位获得的光资源很少,导致棉铃脱落严重;N₂₇₀处理在7果枝及以上高度的PAR光截获仍达0.5~0.9,且在第1果枝处在0.9~1,棉花群体呈现出了良好的光环境。花铃期棉花光合日变化蒸腾速率(Tr)、胞间二氧化碳浓度(Ci)均表现为施氮处理高于未施氮处理,施氮处理间差异不显著,气孔限制值(Ls)刚好与之相反。增加施氮量明显可以减缓光合“午休”现象,但高量施氮处理棉花光合午休现象减缓的力度反而下降,且在达到第2个峰值之后净光合速率(Pn)下降趋势与N₂₇₀处理几乎呈一致。叶片水分利用率(WUE)16:00之后未施氮处理的WUE随时间迅速呈线性下降变化,且逐渐低于施氮处理,实收籽棉产量以N₂₇₀最高为4 835.67 kg/hm²,较N₀、N₄₅₀分别高出7.25%、5.44%。【结论】连续施氮270 kg/hm²,可以获得较优的棉花群体冠层结构,有利于冠层光分布结构,提高光能利用效率,获得较高的产量。

关键词: 棉花, 氮肥, PAR截获率, 冠层结构, 光分布