本研究探討在不同栽植密度及氮肥施用量處理下，水稻全生育期植冠截光效率(light interception efficiency, LIE)及消光係數(extinction coefficient, K)之變化，並評估不同處理因子對相關性狀之影響。試驗結果顯示台稉9號及台農67號兩參試品種在不同期作中, LIE變化型式均相似，雖然在同一氮肥等級下，疏植具有較高的LIE，而中、高密植則LIE明顯較低，但二者間差異不明顯；但隨氮肥之減施，中密度栽植下之水稻LIE顯著低於高密植水稻。在不同氮肥施用等級下，LIE均會呈現隨栽植密度之增加而下降。另在變方分析的結果顯示：期作、氮肥及栽植密度之主效應在消光係數上均呈顯著，但僅期作與栽植密度之交感作用顯著，其它因子間交感作用並不顯著。而在與截光力關係密切之葉片平均傾斜角度(mean tilt angle,MTA)上則呈現期作、氮肥及品種主效應顯著，期作與氮肥、期作與品種及期作與栽植密度等之交感作用顯著，但栽植密度主效應及其它交感作用則不顯著。在相關分析之結果顯示：MTA與LIE呈極顯著之正相關，而與K值呈極顯著之負相關，而此種關係在不同期作及不同品種中均呈現相似結果。
Effects of Planting Density and Nitrogen Rates on the Light Interception Efficiency of Rice Canopy
Lo, J. C.
Different nitrogen application rates and planting densities were used to evaluate their effects on the light interception efficiency (LIE) and extinction coefficient (K) of rice canopy, as well as on some characteristics of rice plants. The result showed that both Taiken 9 and Tainung 67 varities in two crop seasons have similar trend of LIE during the whole growth period. At the same nitrogen application rate, low planting density field showed higher LIE than in medium and high planting density field although they were not statistically different. While the reduction of nitrogen fertilizer applied, low- and medium-density planting rice canopy have significant higher LIE than in the high-density planting canopy. The LIE is gradually decreased following the planting density with different nitrogen application rates. Besides, analysis of variance revealed that main effects of crop season, nitrogen application rates and planting densities were significant on extinction coefficient. The interaction between crop season and plant density was also significant. In addition, main effects of crop season, nitrogen application rates and planting densities were significant on mean tilt angle (MTA), and the interactions of crop season between nitrogen application rates, variety and planting densities on MTA. Correlation analysis showed significant positive correlation between MTA and LIE, and negative correlation between MTA and K.
What is already known on this subject?
The light interception from rice canopy is the critical process for energy conversion during rice growth and production. There are few studies focusing on light interception efficiency in Taiwan.
What are the new findings?
This is the first report to clarify the relationship between light interception efficiency and rice canopy in Taiwan.
What is the expected impact on this field?
According to this finding, it can apply to improve the rice cultivation techniques by enhancing photosynthesis rate and harvest index. The farmer’s profit can be increased by reducing input during rice production.
Key words: Rice, Canopy, Light interception
efficiency, extinction coefficient
Accepted for publication: July 15, 2015