本研究為探討不同氮肥施用量(60、120、180 kg ha-1)對水稻莖稈生長與發育的影響，以水稻品種臺農71號與臺稉9號為試驗材料，於2007及2008年的一、二期作，進行兩年四期作的田間試驗，根據兩年四期作的試驗結果顯示，水稻株高、伸長節間長度、上位五葉之葉鞘長度、葉位與穗位高度以及穗軸抽出程度均隨著氮肥施用量增加顯著提高，其中上位節間及葉鞘長度皆比下位節長，尤其以穗軸節間伸長最大。然而隨著氮肥施用量愈高，葉鞘對伸長節間的包覆程度愈低，主要原因為節間伸長對於氮肥反應的敏感度高於葉鞘所致。葉鞘對伸長節間的包覆程度主要受期作、品種及氮肥施用量的影響，二期作葉鞘長度較一期作長，導致二期作葉鞘對節間的包覆程度明顯較一期作高，但相反地導致二期作具有較短的穗軸抽出度。本研究證實氮肥施用量顯著改變莖桿生長速率，其結果將改變植冠結構與抗倒伏特性。
Effects of Nitrogen Fertilization Rates on the Culm Development of Rice
Chen, R. K. and C. L. Chen
A field experiment was carried out to determine the effects of different nitrogen fertilizer application rates (60, 120 and 180 kg ha-1) on culm development of two rice cultivars TNG71 and TK9 grown in the first and second crop seasons during 2007 and 2008. The two years data across four cropping seasons revealed that culm growth characters such as plant height, length of elongated internodes, length of top five leaf sheath, vertical height of leaf blade and panicle, and panicle exertion above leaf sheath were significantly increased with the increase of application rate of nitrogen fertilizer. Top parts of internode and leaf sheath were longer than lower parts especially for panicle axil internode. However, elongated internode coverage rate by relative leaf sheath decreased significantly with the increase in nitrogen levels owing to the growth of internode response to nitrogen was more sensitive than leaf sheath. Degrees of leaf sheath coverage were affected by crop seasons, cultivars and nitrogen application rates. Leaf sheath coverage rate in second crop season was higher than the first crop season attribute to the total leaf sheath length was longer in the second crop season, and reversely resulted in shorter panicle exsertion. This study indicated that responses of stem growth rate were significantly affected by nitrogen doses and subsequently would change the structure of canopy and lodging resistance.
What is already known on this subject?
Currently, there are lack of detail responses of stem growth to different nitrogen supply under diverse cropping seasons in temperate japonica rice.
What are the new findings?
This research revealed the relationship among nitrogen levels, crop seasons and stem growth of rice. The results can be used to adjust canopy structure and improve lodging resistance.
What is the expected impact on this field?
Understanding the process of stem development under different culture conditions would provide valuable information for nitrogen management, canopy adjustment, and breeding selection.
Key words: Rice, Stem, Morphological traits,
Nitrogen fertilizer application rate
Accepted for publication: September 29, 2015