(8(3-4):21-32)STUDIES ON THE CULTIVATION OF RATOON RICE

本試驗就宿根稻耕種之因子配合數項試驗，自民國44年至民國46年在農試所農場作實際試驗，茲就上述數項試驗結果，綜合其結論如下： 1. 一期作稻•收穫時，稻樁留高者，其萌蘗數較留低者為多。但其萌芽多發生於地上節，故較細弱抽穗早、不整齊，收量亦低。又稱樁高者萌發株數較留低者為多，其相差很明顯。在本試驗內留樁24公分者，萌發率平均為89.1%，留樁15公分者為80.6%，留椿6公分者為71.9%。 2. 稻椿所生長之萌蘗於二期作插秧時再割除一次者，其生育日數則較無割蘗者遲7日左右，惟經過割蘗之處理，其成活株數減少，株高較低，每叢穗數較少，但其穗較長大，收量較佳。 3. 收穫後稻樁伸長之萌芽，培育為宿根稻，以於8月初旬即二期作插秧當時，施行除草施肥管理或割蘗處理者，則施肥除草時同時割除為佳。過遲或過早，對於生育及產量均不良。 4. 一期作稻收穫後，田間排水及灌水之區劃內，灌水區之稻椿萌發株數，似不較排水區為多，但每樁之萌芽數及萌芽高度，均以灌水區為佳。 5. 一期作稻肥料種類不同，對於稻椿之萌發力有很大的差異，單施用堆肥、無氮肥及無肥之處理，其萌發率達99%以上，而稻谷產量除堆肥區較普通肥料區為高外，無氮區並不增加，無肥區則減產很多，多氮區因稻樁之萌發率受影響，故產量極低，經各種肥料處理之宿根稻之產量，一般較其前生稻普通肥料區減低至20~30%。至於多施磷肥，鉀肥或無磷肥鉀肥之處理，對於稻樁之萌發率，均無明顯之增減。 6. 一期作稻收穫前加施少量之氮肥（每10公畝施硫酸錏10公斤），對於稻樁之萌發力有顯著之增加，收穫前14日施者，較不旅者多10%左右，收穫前日數短施者，則相差漸少。但其對於產量之關係，有施用者其產量均無提高之傾向，由表15之結果，收穫前施氣肥對於宿根稻產量不但不增加反而減低。 7. 稻樁伸長之萌蘗於二期稻插秧當時（8月初旬）將稻樁連萌芽距地面約三公分處割除一次之處理，其平均產量較無蘗者高10%左右，全試驗以稻樁留15公分（一般收穫時所遺留之高度）萌蘗除一次之處理者產量最佳。留樁6公分者，則以不割蘗之處理，其產量為佳，平均以留樁15公分處理之產量較留6公分者高12%，惟全試驗各處理間，其最高之產量，每公頃只近23,00公斤，由一般產量而論似嫌太低。 8. 宿根稻之產量由45年及46年2年試驗成績觀察，其收量均較二期作插秧稻為低，在灌水區內，宿根稻之谷產量每公頃1,626.3公斤，二期作稻產量為2,872公斤，其產量只有二期作稻之56.6%，草產量宿根稻每公頃之收量為2,511.1公斤，二期作稻為3,769.5公斤，只為二期作稻之60.6%。在排水區內，無論二期作稻或宿根稻之產量，均較灌水區為低，惟宿根稻對二期作稻之產量比則較灌水區為佳，谷產量為二期作稻之60.5%，草產量為二期作稻之75%。 9. 由各試驗項目內觀察，宿根稻之產量普通低弱，考其原因，宿根稻稻樁萌發株數，以及每枯穗數之減低，似為主要原因，至於如何使萌發株數及每桔穗數之增加以提高收量，似須繼續探討。 10. 在同一田區內，二期作稻比宿根稻之產量為高，然宿根稻之經營，可節省種子及勞力，但是節省若干，有無經濟價值，或在特殊之地區，宿根稻有更大之利益，有待進一步之探討。 1. The present paper describes the experimental result of cultivation of ratoon rice (one of the second generation’s growth from the root) with special emphasis on the effect of different stump heights, irigation and fertilization to the yield. 2. The number of shoots sprouted, seemed to be correlated with height of stump. The rate of tillering in 24 cm, 15 cm and 6 cm stump heights were 89.1%, 80.6% and 71.9% respectively. 3. As the result of once-shoot-cutting treatment, the day of growth prolonged seven days more than that of non-shoot-cutting treatment. The number of ears per hill is decreased but the case is not true the size of ears leading to increase about 10% of yield as compared to non-shoot-cutting treatment. 4. It has been found that the number of hills with shoot sprouts is fewer in irigated plot than that of non-irigated one. However, the number and height of shoots within hills are increased in the irigated plot. 5. Among different kinds and amounts of fertilizers applied on the paddy field of first crop (maternal plant), difference is evident that the tillering ability in manured, nitrogen free and non-fertilization plots were induced increasing to 99%; in case of the grain yield, it has been noticed a little increase in the manured plot, and reduction remarkably in non and super nitrogen and non-fertilization plots of ratoon rice field. However, the yield was generally 20-30% lower than standard fertilizaton plot of maternal plant. No effect on the yield was found as the result of different amount of potassium and phosphorus application. 6. Application of ammonium sulphate (100 kg per ha) to the paddy field of maternal plants 14 days prior to the harvest, resulted 10% increase of rate of shoot sprouting than non-fertilization plot but the decrease of yield was found in maternal plant after this kind of fertilization. 7. Concerning effect of irrigation, the yields of grain and straw of ratoon rice in non-irigated field were found to be 56.6% and 60.6% respectively, in terms those of transplanted and cultured by ordinary method, while in case of irigated field, the result being 60.5% and 75% respectively. 8. As mentioned above, yield of rotoon rice was generally lower than that of ordinary cultivation method. The reduction of number of shoots, and number of ears per hill has been the main reason of low yield of ratoon rice. How to promote these quantitative characters is the key problem of increasing yield of ratoon rice remains to be studied