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利用累積生育度數估測水稻品質及收穫適期
Using growing degree days to estimate quality and optimal havest time in rice
摘要
水稻傳統以計算插秧或移植後天數來決定施肥及收穫的時間點，但其發育情形往往因品種、氣候等因素而有所改變，以插秧後天數無法精準代表生育期。根據研究指出生育度數（Growing Degree Days, GDD）對作物生長發育的相關性可達95%。本研究藉由抽穗後不同收穫時期的生育度數與糙米外觀品質的變化，探討水稻主要栽培品種「臺南11號」、「臺南16號」及「臺中秈10號」之最適收穫時期。試驗結果顯示，此三品種隨著抽穗後生育度數增加，其糙米完整米率有隨之增加的趨勢，後期胴裂粒率增加，導致糙米的完整米率下降。根據抽穗後生育度數與糙米的完整米率之結果，得到其回歸模式，由此模式顯示一期作「臺南11號」、「臺南16號」及「臺中秈10號」分別於抽穗後生育度數733度日、671度日及649度日為最佳收穫時期；二期作分別於抽穗後生育度數718度日、785度日及613度日為最佳收穫時期。過早收穫未熟粒率高，適時收穫才能獲取最高糙米完整米率，獲得最佳稻穀品質。現有技術：現行臺灣水稻收穫時期判斷主要採計算生育日數及穀粒外觀判斷為主。創新內容：利用水稻栽培品種「臺南11號」、「臺南16號」及「臺中秈10號」不同收穫時期糙米外觀品質之變化及累積生育度數，以判斷最佳收穫時期。對產業影響：以生育度數判斷水稻「臺南11號」、「臺南16號」及「臺中秈10號」最佳收穫期，以獲取最佳稻穀品質。
並列摘要
In tradition, farmers counted the number of days after transplanting the rice seedling to determine the time point of fertilization and harvest. However, the number of days after transplanting could not completely represent the growth stage. According to previous research, the growing degree days has 95% correlation with crop growth and development. This study aims to understand the relationship between the different harvesting periods after heading and the head brown rice rate of rice. The goal is to find the optimal harvest time for the main rice cultivars 'Nardares No. 11', 'Nardares No. 16', and 'Taichung sen No. 10'. The results showed that the head brown rice rate of the three tested varieties increased with daily growing degree days (GDD) after heading. The rate of head brown rice decreased in the later growth stage due to the increase of cracking rate. Based on these results, a regression model for predicting the head brown rice rate was developed. This model showed that the GDD of the optimal harvest time of the first cropping season for 'Nardares No. 11', 'Nardares No. 16', and 'Taichung sen No. 10' respectively were 733, 671, and 649 degree days after heading. In the second cropping season, the optimal harvest time for 'Nardares No. 11', 'Nardares No. 16', and 'Taichung sen No. 10' were 718, 785, and 613 degree days, respectively. What is already known on this subject? The current rice field management of the harvesting period in Taiwan is mainly based on the count of growing days and appearance. What are the new findings? Changes in brown rice quality at different harvesting periods for 'Nardares No. 11', 'Nardares No. 16', and 'Taichung sen No. 10' What is the expected impact on this field? Assist the rice field management for the optimum harvest time based on GDD.