(26(1):51-56)STUDIES ON THE EFFECTS OF RICE YIELD AND AGRONOMIC CHARACTERISTICS UNDER LOW TEMPERATURE AND HIGH HUMIDITY CONDITIONS

一、本研究之目的在研討低溫多濕等氣候因予對水稻品種產量與農藝性狀之影響，及試驗自日本引進之早熟品種與本省育成之早、晚熟品種適應性，期選育適應品種推廣山區農民栽培。 二、經人工氣候室溫度控制及於高、低海拔山區桃園縣復興鄉田問試驗結果，可知低溫多濕等氣候因子對稻水品種產量與農藝性狀影響甚大。若氣溫低於20℃及相對濕度超過80％以上，或於第二期作高海拔低溫多濕氣候下，水稻在孕穗期至糊熟期遇此不良氣候環境因子，開花結實則受影響，不稔率增高，產量低落。 三、水稻生長於高海拔低溫多濕環境下，不但產量減低，且影響其生育，株高減低、穗數、一穗粒數、結實率、千粒重、分蘗數均減少，但生育日數略延長。 四、經適應性試驗結果，在本省北部高海拔山區第二期作以自日本引進之早熟品種“Tod orokiwase”較抗低溫多濕不良環境因子，因其具有早熟，較抗病蟲害、分蘗多、不易倒伏等優點，全年兩期作較晚熟品種如台農61號、新竹56號及早熟品種中興11號，Fujiminori等品種產量高達5％左右。 低海拔山區（300公尺左右）第一期稻作似不受低溫影響，如本省新竹地區推廣之新竹56號、台農61號、台南5號、嘉農育11號等品種產量並不低於早熟豐產Todorokiwase品種，然此等品種稻熱病較嚴重，需加強防治方可。 1. Present study is aimed to study the effects of low temperature and high humidity on the yield and growth of rice varieties introduced from Japan as well as from Taiwan, at the same time to select the most suitable high yielding varieties for the mountainous area in Taiwan. 2. It was observed that the low temperature (below 20°C) and high humidity (over 80%) affect greatly on fertility (yield) of rice during the heading stage under controlled temperature and 700 meters of high altitude. (Table 1, 2 and Fig. 1, Fig. 2) 3. Results showed that the low temperature and high humidity affected the plant height, number of tillers and number of panicles of rice plant to be decreased. (Table 1) 4. It was observed that under low temperature and high humidity conditions of mountain district, the early maturing variety “Todorokiwase” was found to be more resistant to this unfavourable conditions. It showed less blast disease and insect, early-maturing, more tillers and lodging-resistant, therefore gave about 5-6% higher grain yield in comparison with the late maturing varieties such as Tainung No. 61, Hsin-chu No. 56 and other early maturing varieties Fujiminori, Chung-Sin No. 11 in the second crop of rice (Table 2) .But it was a little lower yield in the first crop (Table 3)