化學藥劑對龍眼開花之影響

Effects of Chemicals on Flowering in Longan

隔年結果為龍眼栽培上之最大問題，本研究針對隔年結果加以探討，已可控制龍眼開花，克服隔年結果問題，且可進一步周年開花，調節產期。以爆竹內含成分（氯酸鉀與硫磺為主之混合藥劑）處理龍眼植株根部，平均灑於龍眼植株樹冠下樹幹至樹冠內3/4位置，再加以攪拌覆土及澆水至微濕，顯示在不同時間，不同地點對不同龍眼品種，均有催花之效果。於5月及7月於嘉義農業試驗分所試驗園及高雄內門池姓農家果園以藥劑處理分別可達39.8%及75%之開花率。進一步比較爆竹內含成分之效果顯示氡酸鉀為主要促成龍眼開花之有效成分，各種內含氯酸鉀之配方均能促成龍眼花芽分化，且平均開花率可達60%,且藥劑處理效果不受植株生育與葉片生育期之影囓，處理後各生育期之葉片均可能迅速轉成花芽分化而開花，即使在結果狀態下，無果實枝梢亦可花芽分化·植株樹冠直徑6公尺株高4公尺以下使用量約400g。在樹冠直徑6公尺之內，藥劑量400及800g之效果無顯著之差異，均能催花達66%以上。比較·十月,''粉殼＇及·五月'三種品種之效果，顯示五月優於粉殼十月,'但因於不同地區及不同時間處理，不能據以認定品種間效果有差別。

Alternate bearing is a serious problem in longan production in Taiwan. This paper describes the method developed to overcome the alternate bearing by chemical application. The method can control longan flower as required and produce fruit all year round. The gunpowder of firecracker applied to soil 2/3 of canopy from trunk could induce flower initiation in different time, locations and varieties. The treatment could induce 39.8% and 75% of flower in May and July respectively. Further experiments indicated that potassium chlorate is only effective ingredient to force flower in longan in this treatment. Any chemical combined with potassium chlorate studied can induce 60% of flower on the tree in average. The effects of flowering were not affected by stage of leaf development. The flower percentages were not significantly different between 400 and 800 grams of potassium chlorate in trees with 6m of canopy diameter. However, increase of chemical application might increase the flower in longan. The effect was decreased in older and larger tree, which roots were deeper and is more difficult for chemical penetration as well. The results indicated that the flower initiation is irrelative to temperature and leaf development. The flower can be induced by chemical application from root. The research also indicated that flower forcing and season control in longan is possible by low cost chemical.