• 作者： 鄒去潘; 廖雲英; 錢美華; 林燦隆; 陳一心; 王銀波; 蔡國海; 吳來貴; 張萬來; 林富雄; 吳育郎
• 作者服務機構： 中央研究院植物研究所; 台灣大學農藝學系; 中興大學土壤學系; 糧食作物研究所; 新竹會區農業改良場; 台灣農業試驗所嘉義分所; 高雄區農業改良場
• 中文摘要： In Taiwan, the productivity of rice ofthe second crop is generally lower than thatof the first crop. Although there are manyfactors involved in determining the reductionof rice yield in the second crop. Thisstudy is aimed to elucidate these factorsobtained from the five different experiments. 1. Two rice varieties of Taichung 65and Ai-chaw-wu-chien were employed tounderstand the yield and yield componentsbetween the first and the second crop inNankang by using a series of experiments de-signed. (1) Fallowing period was set betweenthe first and the second crop, i.e., fal-lowing 7,14, and 21 days；and the two ad-ditional treatments, i.e., fallowing orplanted sweet potato in the first crop. (2)The rice roots were either removed or notafter the first crop. In the case of riceroot removed from the soil, the grain yieldof the second crop was not increased. Theyield was also not increased by the treat-ment of different fallowings. But, if thesweet potato planted in the first crop, theyield-might be increased that could be dueto the increase of spikelet numbers perpanicle and to percentage of ripenedgrain. The same results were also obtainedby workers from the Dept. of soil, NationalChung-Hsing University, using the same ex-perimental designs at Taichung and Chin-shuei. 2. Generally, the period of the veget-ative in the second crop was shorter thanthat of the first, thus the yield was low,causing by the short vegetative period inthe second crop. Hence, we used two ricevarieties and applied the short-day tech-niques (dark treatment from 17：00 to the8：00 at next day) to control the vegetativeperiod in the first crop. The results showsthat the vegetative periods may shorter in2-3 days than in the check treatment, butthe yield was the same in these two treat-ments. This indicates that the shorter vegetative period was not the main reason todecrease the yield in the second crop. 3. The weather conditions of the firstand the second crop in Taiwan are signific-antly different. Hence, the effect of theweather to the rice growth in two cropwere not the same. We collected the data ofweather conditions and the corresponding17 characters of rice plant in two crop frompast 30 years. The marimax method ofprincipal component analysis was used tostudy the effect of climate on the growthof rice, and the relationship between clim-atic conditions and the determining processof yield. We obtained that the weatherconditions of the ripening stage mostly af-fect the grain yield in the first crop, andthat of the mature stage affect the yieldin the second ones. Additionally, during themature stage the high temperature and lesssunshine may increase the grain yield. 4. From the view point of stability ofrice yield, we planted five japonica andfive indica varieties in five locations, andstudied the genotype-environmental inseract-ion for grain yield and yield components intwo crops. We obtained that the factorwhich affected low yield in the second cropat all five locations was less panicle num-bers per hill. Furthermore, in the northernTaiwan, its also caused by the light testweight, less spikelet number per panicleand the low repening percentage. In thecentral Taiwan i t was caused by the lighttest weight, while in the southern Taiwan,it was caused by the less panicle numberand spikelet number per panicle. Therefore, we need different variety which was also toadapt the different environment conditionand crop season. 5. Four rice varieties are used to com-pare the growth models, growth parametersand yield between the first and the secondcrop in Nankang. We obtained the followingresults：(1)The plant dry matter of thesecond crop was significantly decreased af-ter one month of transplanting as it wascompared with the first crop. This decreasewas caused mainly by the decrease of tillernumbers at the same stage. (2) The maximumgrowth rate of the dry matter (g/plant/day) was found at 9.8 and 15.3 days beforeheading for the first and the second crop, respectively, thus the assimilation of a riceplant at the second crop was depressed quick-ly than that of the first crop. This depres-sing tendency was caused firstly by the leafand than by the stem. Therofore, if wecould delay this depressing time during thesecond crop, the dry matter and the grainyield might be increased. (3) In the first crop,about 86% of yield was obtained from theassimilation after heading, and about 14%by transfer the assimilation substractes fromthe stem and leaf, while the correspondingvalues in the second crop were 79% and21%. Therefore, the assimilated substractesobstained before heading was more importantto the yield in the second crop. (4) The neg-ative genotypic correlation was obtained bet-ween the absolute growth rate at the latetiiling stage and panicle weight, in the firstcrop, however, the positive value was ob-tained in the second crop, and these valuesbetween two crops were significantly differ-ent. (5)The conservational energy for growthwas concerning only with th accumulation ofstraw weight, the correlation was-0.99 forthe first and-0.92 for the second crop,but this energy was not correlated to theformation of the panicle weight．
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