자포니카 초다수성 벼 "보람찬"의 질소이용효율 동태 분석

상완규 ( Wan Gyu Sang ),김영두 ( Young Doo Kim ),강신구 ( Shin Gu Kang ),구본일 ( Bon Il Ku ),이현석 ( Hyun Suk Lee ),이민희 ( Min Hee Lee ),박홍규 ( Hong Kyu Park ),이점호 ( Jeom Ho Lee ) 전북대학교 농업과학기술연구소 2014 농업생명과학연구 Vol.45 No.2

본 연구는 질소시비량에 따른 질소이용효율, 중질소를 이용한 질소시비의 분배와 흡수 구명을 통해 자포니카 초다수성 품종인 ‘보람찬’의 질소이용능을 분석하여 최대수량을 위한 질소시비방법 개선 기초자료로 제공하고자 수행하였다. 다비구의 경우에는 다른 품종들에 비해 보람찬 벼의 잎과 줄기의 질소함량이 비교적 낮은 반면 이삭의 질소함량은 가장 높은 값을 보였는데 이는 보람찬 벼가 다비조건에서 질소 전이율이 높기 때문으로 생각된다. 다비 조건에서 호품, 호농 벼의 질소이용효율(NUE)이 각각 43.7, 41.0인 반면 보람찬 벼는 47.7로 가장 높았으며 질소흡수효율(NUpE), 생리적 질소이용효율(PNUE), 농업적 질소이용효율(ANUE), 질소수확지수(NHI)의 수치도 각각 1.34, 31.3, 16.0, 0.64로 보람찬이 가장 높았다. 각 부위별 시비질소의 흡수량은 부위에 관계없이 기비와 분얼비에서 적었고, 특히 보람찬은 수비 질소의 흡수량뿐만 아니라 흡수된 질소의 이삭 분배율 또한 64%로 다른 품종들에 비해 높았다. 이는 다수성 품종인 보람찬의 시비질소 흡수율과 종실로의 질소 전이율이 다른 품종들에 비해 더 우수하여 다비조건에서 질소시비, 특히 수비시용에 따른 수량 기대효과가 가장 크다는 것을 반증한다. Productive agriculture needs a large amount of expensive nitrogenous fertilizers. Improving nitrogen use efficiency (NUE) of crop plants is thus of key importance. This experiment was conducted to investigate the variation of nitrogen use efficiency, nitrogen uptake efficiency, physiological utilization efficiency in high yield japonica rice ‘Boramchan’ under variable nitrogen levels. Field experiment was conducted at the research farm in National Institute of Crops Science (NICS), Iksan, Korea during 2012∼2013. Four nitrogen levels (0 kg ha-1, 45kg ha-1, 90kg ha-1 and 135kg ha-1) and three Japonica rice varieties (Boramchan, Hopum and Honong) formed the treatment variables. Nitrogen use efficiency of rice cultivars ‘Boramchan’ was 47.7, nitrogen uptake efficiency was 1.3, and physiological N use efficiency was 31.3 in high nitrogen level. And when 135kg ha-1 of nitrogen fertilizer were applied compared to the standard rate of 90kg ha-1, yield and plant dry weight of Boramchan were increased than the others dramatically mainly due to higher number of panicles per m2. Especially Production efficiency(yield/total nitrogen taken up), physiological N use efficiency, agronimic N use efficiency and nitrogen harvest index are higher in ‘Boramchan’ than in the others. In addition, N derived from fertilizer(NDFF) and partitioned N to panicle from fertilizer(PNPF) of ‘Boramchan’ was higher than the others in high nitrogen level.

벼 키다리병 감염 및 발병에 대한 자포니카 벼 품종별 생리적 차이 구명

상완규 ( Wan Gyu Sang ),김영두 ( Young Doo Kim ),강신구 ( Shin Gu Kang ),구본일 ( Bon Il Ku ),이현석 ( Hyun Suk Lee ),이민희 ( Min Hee Lee ),박홍규 ( Hong Kyu Park ),이점호 ( Jeom Ho Lee ) 전북대학교 농업과학기술연구소 2014 농업생명과학연구 Vol.45 No.2

벼 품종에 따른 유묘기 키다리병 발생비율 조사를 위해 남부 평야지에서 재배하는 자포니카 33품종을 대상으로 도장정도와 고사정도를 기준으로 키다리병 발병율을 조사한 결과 남평 등 2품종은 식물체의 1% 이하로 발병하여 키다리병에 저항성이 강한 것으로 나타났으나, 호품 등 9품종은 동일 조건에서 5%이상의 높은 발병율을 보여 키다리병에 대해 감수성인 것으로 나타났다. 키다리병 발병율은 품종에 관계없이 병원균 포자의 농도, 노출시간에 비례하여 증가하며 특히 감수성 품종인 호품벼는 그 증가 속도가 더욱 심함을 알수 있었고 이들 감수성 품종들은 염수선을 통한 종자선정이 특히나 키다리병예방에 중요한 역할을 함을 실험적으로 알수 있었다. 또한 이들 품종간에 지베렐린에 의한 초장 및 중배축 신장 반응 차이가 나타나는 것으로 보아 키다리병 저항성 기작에 지베렐린에 대한 생리적 민감도가 밀접히 연관되어 있음을 추론할수 있다. Rice bakanae disease caused by the fungus Fusarium fujikuroi, is one of the most important rice diseases and distributed widely in Asia. Infected seedlings are elongated, more slender and slightly chlorotic when compared to healthy seedlings by the secretion of gibberillic acid(GA3) from the fungus. But resistant responses of rice culivars was unknown yet. The objective of this study is to compare the response of different cultivars of rice to infection with bakanae and treatment with gibberellic acid. Resistance evaluation of 33 rice varieties against Fusarium fujikuroi was conducted in field seedling test. Finally, Two resistant cultivars(Nampyong, Saenuri) and thirty-one susceptive cultivars(Hopum., etc) were selected. And the length of the elongated seedlings was measured, and the percentage of death of the seedlings after infection was also counted. The disease symptoms such as leaf dryness were appeared in the ``Nampyeongbyeo`` from 30 days at the concentration of 104pores/㎖culturing at 30℃ and then the other varieties withered 20 days after seeding. And susceptive cultivar was more faster than resistant cultivar in seed germination and stem elongation. Thus, a significant correlation might be found between the length of the seedling treated with GA3 and disease injury by bakanae fungus. This study indicated GA related genes might be important resources for improvement of bakanae resistance in rice breeding programs.

연구보문 : 자연과학; 벼 무논점파 재배시 입모 향상을 위한 물관리 방법

최민규 ( Min Kyu Choi ),구본일 ( Bon Il Ku ),강신구 ( Shin Gu Kang ),상완규 ( Wan Gyu Sang ),백남현 ( Nam Hyun Back ),김영두 ( Young Doo Kim ),박홍규 ( Hong Kyu Park ),최원영 ( Weon Young Choi ),박태선 ( Tae Seon Park ),김보경 ( B 한국국제농업개발학회 2013 韓國國際農業開發學會誌 Vol.25 No.3

Water management and weed control in rice direct seeding on puddled paddy surface is important for seedling establishment and early growth. To develop management method for enhancing seedling stands and weed control, three experiments were conducted with rice variety Hopum (midmaturing) at experimental station of National Institute of Crop Science, in Iksan in 2010-2011. In experiment 1, germinated rice seeds were sowed on 1, 2, 3, and 4 days after puddling to find the optimum drying days of paddy surface. The average numbers of seedling stands in 2 and 3 days drying were 117 and 114 per m2, respectively, and those were higher than in the 1 and 4 days. Plant height and root length were increased as drying up to 3 days, but decreased in the 4th day. In experiment 2, non-irrigation and intermittent irrigation started 2, 4, and 6 days after seeding were evaluated. The average numbers of seedlings in intermittent irrigation from 2 and 4 days after seeding were 117 and 113 per m2, respectively. The seedlings in irrigation after 6 days was 92 per m2, and 84 per m2 in non-irrigation. Shoot lengths were highest in the irrigation treatments of 2 days and 4 days after seeding. In experiment 3, herbicide was treated on 10, 12, 14, and 16 days after seeding. Rice seedling and root length was increased in the later herbicide treatments. Weeds were not occurred until the 12 days, but observed in the later two treatments. According to these findings, drying paddy for 3 days after puddling, intermittent irrigating after 2 days from seeding, and herbicide treatment on 12 days after seeding is recommended for direct seeding on puddled paddy surface.

연구보문 : 자연과학; 남부평야지에서 추석전 수확을 위한 벼 생태형별 이앙시기 설정

박홍규 ( Hong Kyu Park ),구본일 ( Bon Il Ku ),강신구 ( Shin Gu Kang ),최민규 ( Min Kyu Choi ),상완규 ( Wan Gyu Sang ),김영두 ( Tae Seon Park ),남정권 ( Young Doo Kim ),박태선 ( Kwon Jeong Nam ),김보경 ( Bo Kyeong Kim ) 한국국제농업개발학회 2013 韓國國際農業開發學會誌 Vol.25 No.3

The price of newly harvested rice before Chusoek, the autumn festival celebrated on the 15th day of the 8th lunar month, is high. However it is difficult for farmers to decide transplanting date with specific cultivars for shipping newly harvested rice before Chusoek because the dates for Chuseok holiday is changing every year based on the Lunar Calendar. This study was conducted to provide farmers a table of rice transplanting dates for each maturity groups by calculating heading dates and ripening periods. The earliest transplanting region were estimated in Daegu and Changwon on April 16, and the latest region was Bonghwa on May 13 when the average temperature for 7 days from transplanting exceeding 15oC. For the early maturity group, days to heading from transplanting were 76 and 57 days when they transplanted on May 10 and June 25, respectively. Average temperatures during the periods were 22.1oC and 25.9oC, respectively. However, accumulated temperature was higher in the earlier transplanting due to longer growing days. For the medium maturity group, days to heading from transplanting were 95 and 72 days when they transplanted on April 21 and June 4, respectively. Average temperatures during the periods were 20.3oC and 24.7oC, respectively. For the mid-late maturity group, days to heading from transplanting were 108 and 82 days in April 20 and May 23 transplanting, respectively. Average temperatures during the period were 21.5oC and 24.0oC, respectively. As the rice growing is available from May 10 (above 16oC) in southern plain area of Korea, rice growers who transplant on May 10 can sell their newly harvested grain as soon as possible from on September 11 with early maturity group, September 24 with medium maturity group, and October 4 with mid-late maturity group.

연구보문 : 자연과학 ; 호남평야지에서 벼 무논점파 재배시 적정 파종기 구명

최민규 ( Min Kyu Choi ),구본일 ( Bon Il Ku ),강신구 ( Shin Gu Kang ),상완규 ( Wan Gyu Sang ),백남현 ( Nam Hyun Back ),김영두 ( Young Doo Kim ),박홍규 ( Hong Kyu Park ),최원영 ( Won Young Choi ),박태선 ( Tae Seon Park ),김보경 ( Bo 한국국제농업개발학회 2012 韓國國際農業開發學會誌 Vol.24 No.3

To recommend optimal rice seeding date for direct hill seeding on puddled paddy surface in Honam plain area, Hopumbyeo (Oryza sativa L.) was seeded 6 times by 10-day interval from April 30 to June 19 in 2009 and 2010. Seedling stand was the highest in two seeding dates, May 20 and May 30, and other seeding dates showed acceptable seedling stand except April 30. Tiller numbers at panicle formation stage were increased up to May 30 and decreased thereafter. Heading date of the seeding on May 20 and May 30 were August 19 and August 23, respectively, and the seeding on June 19 was August 31. In 2009, panicle numbers per m2 was the highest in the seeding on May 20 and decreased in the later seeding dates. However, the seeding on June 19 showed the highest panicle number and the others were not significantly different in 2010. Number of grains per panicle was the highest in the first planting date and was decreasing as seeded later. Milled rice yield was the largest in the seeding date of May 20 in 2009, and in the seedling date of May 30 in 2010. The head rice ratio was increased up to May 20 and similar in the later seeding dates. Protein content was lower in earlier seeding dates. According to the above results, the optimal seeding date of direct hill seeding on puddled paddy in Honam plain area was considered to be May 30. The last seeding date related to the limit date of safe heading was June 19.

남부평야지 이모작에서 벼 무논점파 재배시 파종기에 따른 생육 및 수량

강신구 ( Shin Gu Kang ),최민규 ( Min Kyu Choi ),구본일 ( Bon Il Ku ),상완규 ( Wan Gyu Sang ),이민희 ( Min Hee Lee ),김영두 ( Young Doo Kim ),박홍규 ( Hong Kyu Park ),최원영 ( Won Young Choi ),김보경 ( Bo Kyeong Kim ),이점호 ( Jeom 한국국제농업개발학회 2014 韓國國際農業開發學會誌 Vol.26 No.3

Field experiments were conducted to identify the safe seeding date for rice wet hill direct seeding on puddled paddy surface after barley or wheat cultivation in Honam plain area. Two Korean bred-cultivars, Unkwangbyeo (early maturing) and Dongjin2 (mid-late maturing), were seeded 4 times by 10-day interval from May 25 to June 25 in 2012 and 2013. Seedling stand decreased as seeded later, but it was in optimal range in all the seeding dates. Heading date of the last seeding of Unkwangbyeo on June 25 was August 28, and the last seeding of Dongjing2 on June 25 was September 2, which was within the limit date of heading (September 3). Panicle numbers per m2 were not significantly different until the third seeding on June 15, but it decreased in the seeding date on June 25. Number of grains per panicle decreased as seeded later. Milled rice yield and head rice ratio was also decreased as seeded later, and were the lowest in the last seeding date on June 25. Protein content of Unkwangbyeo was similar regardless of seeding dates, but it increased at later seeding dates in Dongjin2. According to the above results, the seeding date would be recommended within June 25 for Unkwangbyeo, June 15 for Dongjin2 in wet hill direct seeding on puddled paddy in Honam double cropping area.

고품질벼 품종의 등숙기 차광에 의한 광합성 물질 변화

이민희 ( Min Hee Lee ),강신구 ( Shin Gu Kang ),상완규 ( Wan Gyu Sang ),구본일 ( Bon Il Ku ),김영두 ( Young Doo Kim ),박홍규 ( Hong Kyu Park ),이점호 ( Jeom Ho Lee ) 전북대학교 농업과학기술연구소 2014 농업생명과학연구 Vol.45 No.2

최근 육성된 고품질 벼 품종인 보람찬, 호품 및 호농을 공시하여 출수 직후 차광 처리(50, 70%)에 의한 등숙기 일조부족이 광합성능 및 관련 물질 변화와 수량에 미치는 영향을 검토한 결과를 요약하면 다음과 같다. 등숙기 Fv/Fm값은 자연광에서 자란 경우 25일을 기점으로 감소하기 시작하여 55일에는 보람찬이 0.614로 가장 많이 감소하였으나, 차광 처리구에서는 50% 및 70% 모두 0.8 이상을 유지하며 유의적인 변화는 없었다. 등숙기 엽록소 함량은 자연광에서 자란 경우 출수 후 15일 이 지난 시점에 호농 (152), 호품 (146), 보람찬 (130) 순이며, 호농이 보람찬과 호품에 비해 엽록소를 오래 유지하는 것으로 나타났다. 등숙기 차광처리에 의해 천립중과 수량은 차광에 따라 감소하였고, 차광률에 따라 더 높은 감소율을 보였다. 천립중은 세 품종중 호농이 가장 적게 감소하는 경향을 보였다. Sunlight is the main energy source on Earth which is energy used by photosynthesis to convert light energy to chemical energy. In this study, the light use efficiency and photosynthetic characteristics of high-quality rice cultivars after shading on grain filling stage. For the study, we treated of three levels of shade (0, 50 and 70%) on rice at grain filling stage and used three high yielding rice cultivars, such as Hopum, Honong, and Boramchan. The shade was given for the respective plots from heading up to harvesting. We were performed to determine growth survey, SPAD and chlorophyll fluorescence 15, 35, 55 days after shading on grain filling stage. Results of analysis of the results representing the maximum photosynthetic efficiency of PSII, Fv/Fm, and SPAD and were decreased by depending on the time at full sunlight. But shade treatments were not changed and a significant difference among cultivars did not appear. Total Chlorophyll (tChl) and carotenoid (tCar) contents was decreased by depending on the time at full sunlight. Also total chlorophyll content was decreased by level of shade but total carotenoid content was not changed at shading treatment. Rice yield and 1000 grain weight were decreased by depending on the level of shade. Change of 1000 grain weights due to shading treatments was found to be less in Honong than that in Boramchan and Hopum. But rice yields the rate of decrease was not observed the difference between varieties, when protected from light 70%, and decreased to less than 50%.

남부평야지에서 고품질 쌀 생산을 위한 "수광"의 적정 이앙시기

김영두 ( Young Doo Kim ),강신구 ( Shin Gu Kang ),구본일 ( Bon Il Ku ),상완규 ( Wan Gyu Sang ),조서리 ( Seo Ri Jo ),박홍규 ( Hong Kyu Park ),신운철 ( Woon Chul Shin ),고종철 ( Jong Cheol Ko ),양운호 ( Woon Ho Yang ),김보경 ( Bo Kye 한국국제농업개발학회 2015 韓國國際農業開發學會誌 Vol.27 No.1

A field experiment was conducted to determine the optimal transplanting date for ‘Sukwang’, a high grain quality japonica rice, in the southwestern plain area in South Korea. 25-day-old seedlings were transplanted four times by 15 days interval on May 16, June 1, 16, and 30 in 2013 and 2014. Heading dates were August 12 and August 29 in the first and the last transplanting, respectively. Ripening ratio was highest in June 1 and June 16 plots at range of 93 - 94%, and was lowest in 16 May plot. Milled rice yield was the highest in June 1 and June 16 at rage of 538 - 555 kg/10a, and was the lowest in May 16. Head rice yield showed same tendency to milled rice yield. Protein content was not significantly different among treatments except June 1, however, it was slightly increased in the later transplanting plots. Amylose content was increased in the later transplanting plots. According to the regression curve of transplanting dates and grain yield, the optimal transplanting date of ‘Sukwang’ was June 10 in the southwestern plain area in Korea.

호남평야지 청보리-벼 이모작에서 벼 폿트묘 적정 재식밀도 구명

강신구 ( Shin Gu Kang ),김영두 ( Young Doo Kim ),구본일 ( Bon Il Ku ),상완규 ( Wan Gyu Sang ),이민희 ( Min Hee Lee ),박홍규 ( Hong Kyu Park ),이점호 ( Jeom Ho Lee ) 전북대학교 농업과학기술연구소 2014 농업생명과학연구 Vol.45 No.2

본 시험은 호남평야지에서 청보리-벼 이모작 재배시 벼폿트묘에 알맞은 적정 재식밀도를 구명하기 위하여 수행하였다. 관행산파묘와 폿트묘를 이용하여 재식밀도별 생육상황을 보면 경직경은 관계없이 관행보다 폿트묘에서 굵었고, 출수기는 폿트묘 이앙구에서 50주~70주/3.3m2가 관행보다 2일, 80주/3.3m2가 관행보다 1일 정도 빨랐다. 간장은 관행산파묘보다 폿트묘의 간장이 더 컸고, 재식밀도별로는 재식밀도가 낮을수록 간장이 더 크게 나타났으나, 이삭길이는 재식밀도별로 유의한 차이를 보이지 않았다. 이삭수는 재식밀도가 높아질수록 단위면적당 이삭수가 많아지는 경향이었다. 등숙비율 및 천립중은 육묘방법 및 재식밀도 사이에 유의한 차이가 없었다. 백미수량은 재식밀도별로 보면 폿트묘 60주/3.3m2가 543kg/10a로 관행 518kg/10a 보다5% 증수하였다. 완전미 비율은 폿트묘 80주/3.3m2 이앙구에서 다소 낮았고, 육묘방법간에 차이는 없었으나 재식밀도 간에는 다소 차이가 있었던 반면, 아밀로스 함량은 재식밀도 간에 유의한 차이가 없었다. This experiment was carried out to investigate the optimum planting density for rice pot seedling cultivation by machine transplanting in forage barley-rice double cropping system in Honam plain area. Field experiment was conducted at research field of NICS in Iksan in 2012 and 2013. Rice seedling of Chinnongbyeo (mid-late maturing) was raised for 30 days in pot-seedling tray (448 holes) and conventional tray, and transplanted on June 10 in both years. Planting densities of pot seedling were 50, 60, 70, and 80 hills/3.3m2. Conventional tray seedling was transplanted as control at a planting density of 80 hills/3.3m2 on June 10. Tiller number per m was increased as planting density increasing, but stem diameter was decreased. Heading dates of pot seedling plots were August 19 except 80 hills/3.3m2, which were 2 days earlier than the control. Culm length, number of panicle, panicle length, and ripening grain ratio were higher in pot seedling compared to the controls, but 1000-grain weight showed no significant difference. Milled rice yield was significantly different between planting densities. The highest grain yield was 543kg/10a in 60 hills/3.3m2 of pot seedling, and it was 5% higher than its control (518kg/10a). Head rice ratios of pot seedlings and the controls were not significantly different in both transplanting dates.

벼 품종간 엽 생장속도 차이가 생육 및 수량에 미치는 영향

구본일 ( Bon Il Ku ),강신구 ( Shin Ku Kang ),상완규 ( Wan Gyu Sang ),이민희,박홍규 ( Hong Kyu Park ),김영두 ( Young Doo Kim ),이점호 ( Jeom Ho Lee ) 전북대학교 농업과학기술연구소 2014 농업생명과학연구 Vol.45 No.1

본 연구는 이앙시기 변동에 따른 벼 품종들의 출엽특성을 비교하고자 국립식량과학원 벼맥류부 벼시험포장에서 수행되었다. 국내에서 육성되어 재배되는 벼 품종들을 대상으로 출수기까지 벼 출엽속도를 비교해 본 결과 출수기가 늦어질수록 출엽수가 증가하는 경향을 보였다. 그러나 같은 이앙시기에서 동일한 출수를 보여도 벼 품종간 출엽속도의 차이를 보였다. 조생종에서 출수기가 비슷했던 진부벼에 비해 운봉벼는 동일 시기에 1.2엽이 더 전개되었고 중생종에서 광안벼나 화영벼는 간척벼에 비해 각각 1.6엽, 1.4엽이 더 전개되어 품종간 출엽속도의 차이를 보였다. 이앙시기가 늦어짐에 따라 주간에서 전개되는 엽수는 줄어드는 경향이었으나 품종에 따라 증가하는 경우도 있어 일정한 비율로 출엽수가 감소한다고 추정하기는 어려웠다. 다른 품종에 비해 출엽수가 증가하는 경우 출수기 건물중도 높은 경향을 보였으나, 이것은 출엽이 빠른 품종이 생육량을 증대시킨 것에 비해 생육기간 연장에 의해 더 많은 기간 식물체가 영양생장을 하였기 때문으로 판단된다. 5월 16일 이앙하여 7월 20일 전후에 출수한 조생종은 출수후 40일간 평균기온이 약 26℃에서 등숙하였고 6월 15일 이앙에서는 24℃보다 다소 높은 온도에서 등숙하였다. 따라서 출수가 빨랐던 5월 16일 이앙에서는 운봉, 남원, 진부는 수량이 크게 감소한 반면 운광벼는 고온등숙 조건에서도 높은 수량을 나타냈다. 중만생종 벼 품종의 경우 6월 15일 이앙에서 8월 하순에 출수하여 등숙하였는데, 6월 1일과 6월 15일 이앙시 수량을 비교하면 대청벼는 크게 감소했으나 일미벼나 남평벼는 상대적으로 높은 수량을 보여 늦은 출수에 의한 저온 등숙조건에서도 수량성이 양호한 특성을 보였다. This experiment was conducted to compare emergence rate on main culm leaf among cultivars having similar heading date and to evaluate the effects of leaf emergence rate on growth and yield of rice. During 2009~2011, five early maturing rice cultivars(Unbong, Namweon, Jinbu, Unkwang and Sangju), four middle maturing rice cultivars(Seojin, Ganckeok, Hwayeong and Kwangan) and four middle-late maturing rice cultivars(Daecheong, Ilpum, Ilmi and Nampyeong) were transplanted at three different dates from May 16 to June 15 in Iksan region. Number of leaf emerged on main culm increased as heading date delayed, but some rice cultivars having similar heading date showed noticeable difference in emerged leaf number. In transplanting on May 16, the early maturing cultivar, Jinbu, had 1.2 leaf more than Unbong which had similar heading date. Similarly middle maturing cultivar, Kwangan, had 1.6 and 1.4 more emerged leaf than Hwayoung and Gancheok, respectively. As transplanting date delayed, leaf number emerged on main culm decreased in general dates, but some cultivars get increased leaf number in late transplanting dates. Consequently, it was difficult to get a constant rate in leaf number corrected with transplanting date. Cultivars having more emerged leaf number generally had increased dry weight at heading stage, and it is postulated that the increase in dry weight was more contributed by prolonged growth duration than by leaf emergence rate. In transplanting on May 16, early maturing cultivars, Unbong, Namweon and Jinbu showed significant yield decrease compared to yield in transplanting on June 15 because of high temperature during ripening stage, but Unkwang showed least reduction in yield. In transplanting on June 15, middle-late maturing cultivars, yield of Daecheong showed significantly reduced compared to that in transplanting on June 1 because of low temperature during ripening stage, but Ilmi and Nampyeong showed slight reduction in yield.