台灣毛豆、甜玉米經濟產量之適栽度分析及未來調適之研究

Abstract

全球氣候暖化趨勢日益明顯，作物栽培將受到更多衝擊。氣溫上升對台灣主要的糧食作物-水稻之產量與品質的影響已有許多研究，而甜玉米、毛豆是台灣重要的經濟雜糧作物，卻少有相關研究。因此，本研究選用毛豆高雄9號及甜玉米白美人品種進行分析，以歷史栽培資料應用線性模型進行分析，探討台灣毛豆及甜玉米的氣象適栽條件，並結合地理資訊系統，分析於未來暖化情境下的雜糧作物氣候適栽區與適栽時期。研究中推測的暖化情境包含基期年、暖化情境RCP4.5、及RCP8.5；除基期年外，各情境又包含世紀初至世紀末，近、中、遠三個期程。 本研究結果顯示，毛豆的合格莢率與籽粒充實期的平均溫度有顯著相關，其最適溫度24 °C。毛豆秋作栽培普遍優於春作，且台灣西部優於東部，適栽地區變化情形，基期年以高屏、雲嘉地區，溫度適宜且日射量充足，為最適栽培地點選擇，與現在毛豆主要產區相同。但至暖化嚴重的RCP8.5世紀末期，西部地區之氣溫上升後較不適宜栽培，反之，東部地區則因暖化提升其溫度適宜度。而甜玉米結果顯示，於生育敏感期的雄花抽穗至雌花抽絲間，平均溫度20 °C之下，及累積日射量達430 MJ/m2，將有最高優良品 (A級) 的單位面積產量。甜玉米的春作普遍栽培優於秋作栽培，推測原因為白美人屬溫帶型玉米，同時也呼應目前台灣甜玉米於裡作的產量最高之情形。甜玉米最佳栽培地區的變化由基期年的中彰投以南地區，其兼具氣溫合適及日射量充足，但至暖化末期，以嘉義地區所受衝擊最小，其溫度適宜與日射量亦充足，成為暖化下較適宜栽培的地點。各地栽培期的調適策略上，毛豆及甜玉米的變化趨勢相同，建議春作較現今播種期提前，秋作則是延後栽培。 最後，本研究依據適栽期的結果，將秋作9-11月以及春作12-2月的基期年適栽地圖，疊合適宜兩作物的栽培區，以顯示不同月份的雜糧適栽區變化。結果顯示基期年秋作以9月份，春作於1月下旬至2月上旬間，為全台皆適宜的雜糧播種期，並以彰化、雲林的適宜栽培期最長。本篇研究基於適地適種的目標，探討台灣因應氣候變遷的雜糧栽培調適策略，結果預期能提供未來經濟雜糧作物栽培專區規劃之參考，另一方面仍需透過育成耐熱、耐蔭及高產等品種，以達到減緩氣候對未來台灣雜糧作物生產之衝擊。

Rising air temperature and decrease of solar radiation caused by global warming had brought up more challenge for crop cultivations in recent years, including vegetable soybean and sweet corn. However, the influence of global warming on vegetable soybean and sweet corn in Taiwan were seldom reported. In order to propose adaptive strategies for vegetable soybean and sweet corn cultivation under global warming. vegetable soybean KS.9 and sweet corn Bai-Mei-Ren serve as the target varieties in this research. First, optimal temperature and cumulated radiation in sensitive developing stages of these two crops were analyzed by linear and quadratic model. Then, suitable zone/period under different climate scenarios were projected in Geographic Information System (GIS) software, including four times series which are baseline (1985-2005), near-term (2016-2035), mid-term (2046-2065) and far-term (2081-2100), and two global warming scenarios of RCP4.5 and RCP8.5. For vegetable soybean, results suggest that the graded pod rate had significant quadratic relation with average temperature in seed-filling (R5-R6) stage, and its optimal temperature was 23-24 °C. In general, suitability of 2nd crop seasons was better than 1st crop seasons. During baseline, Kaohsiung, Yunlin and Chiayi were very suitable zone (displayed in dark green) due to optimal temperature and sufficient solar radiation, which were identical to major cultivate area nowadays. However, the very suitable zone will shift to eastern Taiwan in far-term (2081-2100) under scenario RCP8.5. As for sweet corn, 20°C was the optimal temperature of anthesis-silking interval (ASI) for yield of grade A sweet corn. Suitability was better in 1st crop seasons, which also match the current situation in Taiwan. During baseline, central of southern Taiwan was the suitable zone (displayed in light green). However, only the central of Chiayi remains suitable for sweet corn when it comes to the far-term (2081-2100) of scenario RCP8.5. According to our study, adjustment of planting periods for both crops were identical. For 1st crop season, advance planting dates could in the, on the other hand, it would be better to delay planting dates in the 2nd crop season. At last, according to the result of baseline suitable periods, the suitable zones of two crops are overlaid. The results show that the suitable planting periods for most regions are September in 2nd crop season, and in the 1st crop season is the late January to the early February. Among these suitable zones, Yunlin and Changhua have the longest suitable periods. Both scenario RCP4.5 and RCP8.5. Under climate changes, crop suitability analysis in our study could provide advices for cultivation adjustment, and point out the suitable periods and regions in Taiwan. Moreover, breeding high yield, heat tolerant and low radiation demands variety is important to mitigate the negative effect of global warming.