고품질 쌀 생산을 위한 질소비료절감 재배시 품종특성별 최적 재식밀도를 구명하고자 '06년부터 '08년에 수수형 품종과 수중형 품종을 공시하여 벼 생육, 수량 및 등숙특성 등을 검토한 결과 가. 당 경수는 밀식함에 따라 많아졌고, 품종간에는 호평벼가 많고 신동진벼가 적었다. 엽색값은 재식밀도간 차이가 없이 동진1호가 높았고, 엽면적 지수는 밀식함에 따라 높아졌으며, 품종간에는 호평벼가 가장 높았다. 줄기 건물중 증가 정도는 동진벼와 호평벼는 3.3 m2당 90주에서 현저히 증가하였으나 신동진벼는 재식밀도 증가에 비례적으로 증가하는 경향이었다. 나. 재식밀도 증가에 따른 이삭수의 증가정도는 동진1호와 호평벼가 높고, 신동진벼가 낮았다. 유효경비율은 재식밀도가 증가함에 따라 다소 낮아지는 경향이었으며, 품종간에는 경수가 많았던 호평벼가 낮았다. 전체 건물중에서 잎이 차지하는 비율은 대체로 밀도가 증가함에 따라 다소 낮아지는 경향이었으며, 품종간에는 동진1호가 가장 높았다. 다. 완전립 비율은 공시품종 모두 재식밀도가 높아짐에 따라 낮아지는 경향으로, 특히 3.3 m2당 90주 이상에서 현저하였다. 단백질 함량은 재식밀도간 큰 차이가 없고 품종간에는 신동진벼가 낮았다. 라. 쌀 수량은 수중형인 동진1호와 신동진벼는 3.3 m2당 90주를 심으면 80주 이하를 심는 것이 비해 쌀 수량은 약간 높아지지만 완전미 수량은 차이가 없었으며, 수수형인 호평벼는 재식밀도간 완전미 수량 차이가 없었다. 따라서 질소감비 조건에서는 수중형 품종인 신동진벼와 동진1호는 3.3m2 80주를 심고, 수수형 품종인 호평벼는 70주를 심는 것이 완전미를 생산하는데 가장 유리한 것으로 나타났다. 마. 벼 품종별 재식밀도에 따른 이삭당 분화 영화수는 공시품종 모두 밀식함에 적어지는 경향이었으며, 품종간에는 동진1호> 신동진벼> 호평벼 순으로 많았다. 바. 이삭당 1차지경수와 1차지경착생 영화수는 신동진벼가 각각 10.06, 60.4개로 가장 많았고, 호평벼가 8.87, 53.1개로 가장 적었다. 사. 총 유관속수에 대한 대유관속수 비율은 신동진벼가 32.6%, 호평벼 34.0%, 동진1호가 34.8%였으며 재식밀도가 증가함에 따라 대유관속수 비율도 증가하는 경향이었다.

This experiment was carried out to determine the optimum planting density for rice pot seedling cultivation in wheat-rice double cropping system in Honam plain area. A mid-late maturing rice variety ‘Chinnong’ was raised in pot seedling tray and conventional tray for 30 days, and then transplanted on June 25 in 2012 and 2013. Four different planting densities (15.2, 18.9, 21.6, and 25.3 hills per m 2 ) in pot seedlings were applied as treatment. Conventional tray seedling was implicated as control at a single planting density of 27.8 hills per m 2 . In this experiment, the number of effective tillers was increased as planting density increasing, but stem diameter was decreased. Pot seedling showed higher stem diameter and effective tillers than the control. Heading dates of pot seedling plots were not significantly different between the planting densities but 2 days faster than the control. Culm length, number of panicles, panicle length, and ripening grain ratio were higher in pot seedling compared to the control, but 1000-grain weight showed no significant difference. Milled rice yields in pot seedlings ranged from 5.19 to 5.43 t ha -1 , and the highest yield was observed in 21.6 hills per m 2 . Head rice ratios in pot seedlings and the controls were not significantly different. Above results on planting density of rice pot seedling cultivation would be applicable to wheat-rice double cropping and also to late transplanting cultivation of rice single cropping.

The time of panicle initiation change by transplanting date, and this change is affected by heading ecotype and seedling age. So we assessed the variations of panicle initiation, spikelet differentiation and heading date affected by transplanting dates, rice cultivars and seedling ages. And we compared the growth durations and meterological factors between chief growth stages. The differences of growth duration from transplanting date to spikelet differentiation by seedling age were 1~3 days in all transplanting of Unkwang, but it increased to 4 days in Hwayeong transplanting on May 1 and June 30, and Nampyeong transplanting on June 30. The growth durations from panicle initiation to heading of Unkwang and Hwayeong increased until transplanting time by May 31, and decreased thereafter. The growth durations of Nampyeong increased in transplanting on May 16 and May 31. In each transplanting, mean temperature of 30 days after heading was highest in early transplanting, but sunshine hours in the period were highest in transplanting on June 30 in Unkwang, in transplanting on June 15 in Hwayeong, and higher in transplanting on May 31 and June 15 in Nampyeong. The growth duration between spikelet differentiation and heading showed variation according to rice cultivars and transplanting date, Those were 22~26 days in Unkwang, 21~27 days in Hwayeong and 21~28 days in Nampyeong.

A field study was conducted to understand nitrogen use efficiency of high yielding Japonica rice varieties under three levels of nitrogen fertilizer (90, 150 and 210 kg N ha -1 ) in Iksan, Korea. Two high yielding rice varieties, Boramchan and Deuraechan, and an control variety, Dongjin2, were grown in fine silty paddy. Nitrogen use efficiencies (NUE) were 83.3, 56.3, and 41.2 in 90, 150, and 210 kg N ha -1 fertilizer level, respectively. Total nitrogen uptake varied significantly among nitrogen levels and varieties. Variety Dongjin2 showed the highest nitrogen uptake efficiency (NUpE), while Boramchan and Deuraechan showed higher nitrogen utilization efficiency (NUtE). However, Nitrogen harvest index (NHI) was higher in Boramchan (0.58) than Deuraechan (0.57) and Dongjin2 (0.53). Rough rice yield showed linear relationship with total nitrogen uptake (R 2 =0.72) within the range of nitrogen treatments. Boramchan produced significantly higher rough rice yield (8546 kg ha -1 ) which mainly due to higher number of panicles per m 2 compared to Deuraechan (7714 kg ha -1 ). Deuraechan showed higher number of spikelets per panicle, but showed lower yield due to lower number of panicle per m 2 . Rice varieties showed different nitrogen uptake ability and NUE at different nitrogen level. Plant breeders and agronomist should take advantage of the significant variations and relationships among grain yield, NUpE, and NUE.

This study was performed at Rice and Winter Cereal Crops Department of NICS during 2007 and 2008 to investigate the characteristics of rice leaf emergence and to obtain basic data which can be used for rice growth simulation model by which we can forecast rice growth stage and heading date accurately under different cultivars, transplanting date, and climatic conditions. To confirm leaf emergence rate according to rice maturing ecotype, we surveyed the leaf emergence rate and heading date of Unkwangbyeo, Hwayoungbyeo and Nampyeongbyeo which are early maturing, medium maturing and medium-late maturing cultivars, respectively, according to seedling raising duration and transplanting time. When seedling duration was 15 days, the growth duration between transplanting time and completion of flag leaf emergence on main culm were 51.5~78.3 days in Unkwangbyeo, 55.3~87.9 days in Hwayoungbyeo and 58.4~98.4 days in Nampyeongbyeo, respectively. When seedling duration was 30 days, they were 50.1~75.5 days in Unkwangbyeo, 52.4~84.7 days in Hwayoungbyeo and 56.4~93.8 days in Nampyeongbyeo, respectively. As transplanting time delayed, the emerged leaf number after transplanting decreased in all rice cultivars. The cumulative temperature between transplanting time to completion of flag leaf elongation on main culm were 1,281~circC~1,650~circC in Unkwangbyeo, 1,344~circC~1,891~circC in Hwayoungbyeo and 1,454~circC~2,173~circC in Nampyeongbyeo, respectively. Leaf emergence rate on main culm were precisely represented by equation, y = y0 + a / [1 + exp( - (x - x0 ) / b)]c, when we used daily mean temperature as variable.

This study was carried out to confirm the effects of climate change to growth, yield and quality of rice by the global warming. By the study of Korea Meteorology Administration, the temperature of Korea increased 0.95℃ during last 34 years and the width of temperature increase be on an increasing trend gradually. As temperature increases, rice is faced with critical change such as growth duration shortening, heading acceleration, yield decrease and quality deterioration. So, we studied the rice growth and yield change by the temperature increase. To confirm the effects of temperature increase, rice cultivars such as early maturing Unkwangbyeo, medium maturing Hwayoungbyeo and late maturing Nampyeongbyeo were transplanted on 1, 15, 30 of June inner transparent vinyl house which was treated by different temperature. The increased mean temperature were 1.4℃～3.5℃, respectively, compared to outer field. The growth duration from transplanting to heading were shortened by the temperature increase. In June 1 transplanting, especially the growth duration of early maturing Unkwangbyeo was shortened greatly by temperature increase. As temperature increases, rice yield decreased in most cases. In 1.4℃ temperature increase, rice yield of June 15 transplanting were higher than those of other transplanting, but in 2.1℃ or more temperature increase, the rice yield of June 30 transplanting were similar or more than those of other transplanting.

To select rice cultivars adaptable to low fertilization in puddled soil drill seeding, 20 rice cultivars were tested in Iksan. The seedling stand ratio of Kwanganbyeo, Junganbyeo, Saegyehwabyeo, Pyeonganbyeo were higher than 80%, but those of Hwalangbyeo, Hoanbyeo were lower than 60%. The tiller number per m2 was 4% smaller in low fertilization compared to conventional fertilization level. In low fertilization, the decrease rate of tiller number per m2 were less than 1～2% in Ansanbyeo, Juan 1, Geumanbyeo and Hoanbyeo, but more than 6～9% in Junganbyeo, Hwaanbyeo, Daesanbyeo and Saegyehwabyeo. Harvest index was 2.8% higher in low fertilization compared to conventional fertilization level. Nonganbyeo, Hopumbyeo, Dongjin 2 and Saegyehwabyeo showed high harvest index, but Gwanganbyeo, Geumanbyeo and Hwalangbyeo showed low harvest index. In low fertilization, milled rice protein content were lower than 6.0% in 14 rice cultivars including Juanbyeo and Kwanganbyeo, but 6.1～6.4% in other rice cultivars. Rice yield decreased 6% in low fertilization compared to conventional fertilization. Rice yield decrease were smaller as 2～3% in Hoanbyeo, Juanbyeo, Kwanganbyeo, Chengdambyeo, Geumanbyeo and Donganbyeo, but bigger as 7～8% in Nonganbyeo, Nonghobyeo. Dongjin 2, Saegyehwabyeo and Ansanbyeo. Owing to 2.4% increase of head rice ratio in low fertilization compared to conventional fertilization, head rice yield decreased 4% in low fertilization. Cultivating rice in puddled soil drill seeding with low fertilization, the rice cultivars such as Kwanganbyeo, Hopumbyeo, Pyeonganbyeo and Dong 2 showed lower than 6.0% milled rice protein content and more than 470㎏/10a milled rice yield.

This study was conducted to investigate the variation of rice quality and the effect of labor-saving by using slow-releasing fertilizer when doing direct drill seeding on flooded paddy surface by large scale direct drill seeding machine in Honam plain area. The results obtained by changing the amount of slow-releasing fertilizer in 2008, 2009 are as follows. Considering rice growth, head rice yield and rice quality, the optimum amount of slow-releasing fertilizer was 7kg/10a, when doing direct drill seeding on flooded paddy surface in southern plain area of Korea. When using slow-releasing fertilizer 7kg/10a, the protein content became lower, and head rice ratio became higher than that of conventional nitrogen split application method as basal fertilization, top dressing at tillering stage, fertilization at panicle initiation stage.

This study was conducted to select suitable rice cultivars for high-quality rice production in silage barley-rice double cropping in Honam plain area by National Institute of Crop Science from 2008 to 2009. Heading dates of all tested cultivars were before the safe heading limit(Aug. 31). Rice yield was superior in "Keunseom", "Hanareum", "Hanmaeum", "Onnuri", "Hopum", "Juan 1", "Dongjin 1", and was little in "Daepyeong", "Hwasin", "Malgeumi", "Chilbo", "Nampyeong", "Hopyeong". Protein content was high in "Hanareum", "Keunseom", "Chilbo", "Nampyeong", and was low in "Hanmaeum", "Dami", "Sindongjin", "Pyeongan", "Samgwang". And head rice ratio was high in "Malgeumi", "Hwanggeumnuri", "Samgwang", and was low in "Keunseom", "Hanareum", "Dami", "Hanmaeum", "Hwasin". In consideration of all the factors, in conclusion, proper cultivars for silage barley-rice double cropping are "Onnuri", "Hwanggeumnuri", "Hopum", "Dongjin 1", "Juan 1".

This study was conducted to examine the appropriate transplanting date of the top-quality rice variety, Unkwangbyeo, in Honam plain area. The results obtained from 2006 to 2007 in Iksan are as follows. The number of panicle per m2 increased as the transplanting date became late and the number of grain per m2 was the highest in the plot of which the transplanting date was June 15. Percent ripened grain increased as the transplanting date became late until June 15, however, it decreased in the plot of which the transplanting date was June 30. Imperfect grain increased as the transplanting date became early due to the occurrence of immature rice and cracked rice. Protein content increased as the transplanting date became late, but didn't show statistical significance. Toyo texture increased as the transplanting date became late. Rice yield and the head rice yield increased as the transplanting date became late until June 15, however, they decreased in the plot of which the transplanting date was June 30. Even though the rice price was high in early transplanting cultivation, gross profit was the highest in June 15 transplanting since the rice yield increased as the transplanting date became late until June 15. Considering the yield, rice quality and profit, the most appropriate transplanting date of Unkwangbyeo in Honam plain area is the middle of June.

This study was carried out to investigate the proper interval of water exchange according to nitrogen fertilizer level at medium saline soil which are 0.3 or more soil salinity in southwestern reclaimed saline land. The nitrogen fertilizer level were 14, 17, 20kg per 10a, and the interval of water exchange were every 3, 6, 9 days after transplanting. The summarized experimental results are as follows. The salinity were maintained as low when the interval of water exchange were every 3 or 6 days after transplanting, but salinity was highest at rooting stage, and decreased from that, so salinity were about 0.3 at panicle initiation stage or ripening stage when the interval of water exchange was every 9 days after transplanting. The rice yield were 537-552kg/10a when the interval of water exchange was every 3 days with 17-20kg/10a nitrogen fertilizer level, and 519-533kg/10a when the interval of water exchange was every 6 days with 17-20kg/10a nitrogen fertilizer level, but decreased outstandingly in the other treatments. Considering the yield and salt injury at medium saline soil at southwestern reclaimed saline land, proper nitrogen fertilizer level was 17-20kg/10a when the interval of water exchange were every 3 or 6 days after transplanting.

This study was carried out to investigate the optimum application time of basal fertilization in direct-seeded rice on flooded paddy surface at medium saline soil in southwestern reclaimed saline area which is Munpo series and have 0.3 or more soil salinity. The nitrogen fertilizer level were 14, 17, 20kg per 10a, and the basal fertilization were applied before sowing, 10, 20, 30 days after sowing along with topdressing at tillering stage, respectively. The summarized experimental results are as follows. Seedling stand was proper when basal fertilization was applied before sowing, but lower than appropriate seedling stand when basal fertilization were applied 10, 20, 30 days after sowing along with topdressing at tillering stage. The rice yield were 509-541kg/10a when 14-20kg/10a basal fertilization was applied before sowing, and 368-481kg/10a when basal fertilization were applied 10, 20, 30 days after sowing along with topdressing at tillering stage. Considering the yield and salt injury at medium saline soil in southwestern reclaimed saline area, the application of basal fertilization before sowing was superior for improving seedling stand, and 14-20kg/10a fertilization rate was allowable.

This study was carried out to develop rice growth model when cultivate early maturing rice cultivar, Unkwangbyeo, in Honam plain area. To confirm leaf emergence rate and variation of heading date, we transplanted 15 day and 30 day old seedling on May 1, May 15, May 31, June 15, June 30, respectively. The growth duration between transplanting and completion of leaf emergence on main culm were 50.1~78.3 days in 2007 and 47.5~74.7 days in 2008. Growth duration diminished gradually as transplanting time delayed, but the difference of growth duration by transplanting time were more bigger than that of seedling day. The emerged leaf number after transplanting on main culm were 8.9~10.9 in 2007 and 8.4~10.9, respectively. The emerged leaf number diminished as transplanting time delayed, but the difference of emerged leaf number by transplanting time were more bigger than that of seedling day. The cumulative temperature between transplanting and completion of leaf emergence on main culm were 1,281~1,650℃ in 2007 and 1216~1560℃ in 2008. The solar radiation between transplanting time and completion of leaf emergence on main culm were 709~1,245MJ/㎡ in 2007 and 722~1,220 MJ/㎡ in 2008. The sunshine hours between transplanting time and completion of leaf emergence on main culm 234~433 hours and 238~431 hours, respectively.

This study was carried out to attain the basic data which will be used in the selection of adaptable varieties in honam plain area for the production of high quality rice. 12 varieties including Unkwang, Hwayeoung and Nampyeong were tested in southern plain area, Iksan. The number of panicles per ㎡ was the highest in Hopyeong, the lowest in Sindongjin, and that of other varieties was around 350. The mean percentage of effective tillers was the highest in early maturing varieties, the lowest in Ilpum, Nampyeong and Junam, and that of other varieties was around 75%. The number of total seeds was the highest in Hopyeong which had the high number of panicle per ㎡ and in Dongjin 1 which had the high number of seeds per panicle. That of Hwayeong, Sindongjin and Odae was the lowest, respectively. Percent ripened grain of the early maturing varieties was lower than the medium maturing and medium-late maturing varieties showing 93% in Hwayeong, Ilmi and Samkwang which is the highest, and 83% in Unkwang which is the lowest. Head rice ratio was high in Nampyeong, Hwayeong and Ilmi, and low in early maturing varieties, Unkwang and Odae. Protein content was high in Odae, Hwayeong and Nampyeong, and low in Sindongjin, Samkwang and Pyeongan. The rice yield was high in Sindongjin, Unkwang, Ilmi and Dongjin 1 showing more than 500kg/10a, while the head rice yield was high in Nampyeong, Dongjin1 and Sindongjin, and low in Ilpum and Odae.