• KOREAN JOURNAL OF CROP SCIENCE
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• v.3
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• pp.1-40
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• 1965

To measure variations in some of the important agronomic characteristics of rice varieties under shifting of seedling dates, this study has been carried out at the Paddy Crop Division of Crop Experiment Station(then Agricultural Experiment Station) in Suwon for the period of three years 1958 to 1960. The varieties used in this study were Kwansan, Suwon ＃82, Mojo, Paltal and Chokwang, which have the different agronomic characteristics such as earliness and plant type. Seeds of each variety were sown at 14 different dates in 10-day interval starting on March 2. The seedlings were grown on seed bed for 30, 40, 50, 60, 70 and 80 days, respectively. The results of this study are as follows: A. Heading dates. 1. As the seeding date was delayed, the heading dates was almost proportionally delayed. The degree of delay was higher in early varieties and lower in late varieties and the longer the seedling stage, the more delayed the heading date. 2. Number of days to heading was proportionally lessened as seeding was delayed in all the varieties but the magnitude varied depending upon variety. In other words, the required period for heading in case of late planting was much shortened in late variety compared with early one. Within a variety, the number of days to heading was less shortened as the seedling stage was prolonged. Early variety reached earlier than late variety to the marginal date for the maximum shortening of days to heading and the longer the seeding stage, the limitted date came earlier. There was a certain limit in seeding date for shortening of days to heading as seeding was delayed, and days to heading were rather prolonged due to cold weather when seeded later than that date. 3. In linear regression equation, Y=a+bx obtained from the seeding dates and the number of days to heading, the coefficient b(shortening rate of days to heading) was closely correlated with the average number of days to heading. That is, the period from seeding to heading was more shortened in late variety than early one as seeding was delayed. 4. To the extent that the seedling stage is not so long and there is a linear relationship between delay of seeding and shortening of days to heading, it might be possible to predict heading date of a rice variety to be sown any date by using the linear regression obtained from variation of heading dates under the various seeding dates of the same variety. 5. It was found out that there was a close correlation between the numbers of days to heading in ordinary culture and the other ones. When a rice variety was planted during the period from the late part of March to the middle of June and the seedling ages were within 30 to 50 days, it could be possible to estimate heading date of the variety under late or early culture with the related data of ordinary culture. B. Maturing date. 6. Within (he marginal date for maturation of rice variety, maturing date was proportionally delayed as heading was delayed. Of course, the degree of delay depended upon varieties and seedling ages. The average air temperature (Y) during the ripening period of rice variety was getting lower as the heading date. (X) was delayed. Though there was a difference among varieties, in general, a linear regression equation(y=25.53-0.182X) could be obtained as far as heading date were within August 1 to September 13. 7. Depending upon earliness of a rice variety, the average air temperature during the ripening period were greatly different. Early variety underwent under 28$^{\circ}C$ in maximum while late variety matured under as low as 22$^{\circ}C$. 8. There was a highly significant correlation between the average air temperature (X) during the ripening period, and number of day (Y) for the maturation. And the relationship could be expressed as y=82.30-1.55X. When the average air temperature during the period was within the range of 18$^{\circ}C$ to 28$^{\circ}C$, the ripening period was shortened by 1.55 days with increase of 1$^{\circ}C$. Considering varieties, Kwansan was the highest in shortening the maturing period by 2.24 days and Suwon ＃82 was the lowest showing 0.78 days. It is certain that ripening of rice variety is accelerated at Suwon as the average air temperature increases within the range of 18$^{\circ}C$ to 28$^{\circ}C$. 9. Between number of days to heading (X) related to seeding dates and the accumulated average air temperature (Y) during the ripening period, a positive correlation was obtained. However, there was a little difference in the accumulated average air temperature during the ripening period even seeding dates were shifted to a certain extent. C. Culm- and ear-lengths. 10. In general all the varieties didn't show much variation in their culm-lengths in case of relatively early seeding but they trended to decrease the lengths as seeding was delayed. The magnitude of decreasing varied from young seedlings to old ones. Young seedlings which were seeded during May 21 to June 10 didn't decrease their culm-lengths, while seedlings old as 80 days decreased the length though under ordinary culture. 11. Variation in ear-length of rice varieties show the same trend as the culm-length subjected to the different seeding dates. When rice seedlings aged from 30 to 40 days, the ear-length remained constant but rice plants older than 40 days obviously decreased their ear-lengths. D. Number of panicles per hill. 12. The number of panicles per hill decreased up to a certain dates as seeding was delayed and then again increased the panicles due to the development of numerous tillers at the upper internodes. The seeding date to reach to the least number of panicles of rice variety depended upon the seedling ages. Thirty- to 40-day seedlings which were seeded during May 31 to June 10 developed the lowest number of panicles and 70- to 80-day seedlings sown for the period from April 11 to April 21 reached already to the minimum number of panicles. E. Number of rachillae. 13. To a certain seeding date, the number of rachillae didn't show any variation due to delay of seeding but it decreased remarkably when seeded later than the marginal date. 14. Variation in number of rachillae depended upon seedling ages. For example, 30- to 40-day old seedlings which, were originally seeded after May 31 started to decrease the rachillae. On the other hand, 80-day old seedlings which, were seeded on May 1 showed a tendency to decrease rachillae and the rice plant sown on May 31 could develop narrowly 3 or 4 panicles. F. Defective grain and 1.000-grain weights. 15. Under delay of the seeding dates, weight of the defective grains gradually increased till a certain date and then suddenly increased. These relationships could be expressed with two different linear regressions. 16. If it was assumed that the marginal date for ripening was the cross point of these two lines, the date seemed. closely related with seedling ages. The date was June 10- in 30- to 40-day old seedlings but that of 70- to 80-day old seedlings was May 1. Accordingly, the marginal date for ripening was getting earlier as the seedling stage was prolonged. 17. The 1.000-grain weight in ordinary culture was the heaviest and it decreased in both early and late cultures. G. Straw and rough rice weights. 18. Regardless of earliness of variety, rice plants under early culture which were seeded before March 22 or April 1 did not show much variation in straw weight due to seedling ages but in ordinary culture it gradually decreased and the degree was became greater in late culture. 19. Relationship between seeding dates (X) and grain weight related to varieties and seedling ages, could be expressed as a parabola analogous to a line (Y=77.28-7.44X$_1$-1.00lX$_2$). That is, grain yield didn't vary in early culture but it started to decrease when seeded later than a certain date, as seeding was delayed. The variation was much greater in cases of late planting and prolongation of seedling age. 20. Generally speaking, the relationship between grain yield (Y) and number of days to heading (X) was described with linear regression. However, the early varieties were the highest yielders within the range of 60 to 110, days to heading but the late variety greatly decreased its yield since it grows normally only under late culture. The grain yield, on the whole, didn't increase as number of days to heading exceeded more than 140 days.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.4
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• pp.388-397
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• 1985

Forage productivity and sequential changes in forage quality of four rye and two triticale varieties were studied. All the observed characteristics were similar among rye or triticale varieties, but they were different between rye and triticale varieties. Early growth of rye was better compared to triticale varieties, but at heading stage yield in dry weight, digestible dry matter and percent dry matter of triticale were higher compared to rye varieties. Heading stage of rye was earlier than that of triticale by 11 - 14 days. Triticale had longer and broader leaf blades and a higher leaf blade/total dry weight ratio compared to rye. Protein content decreased as plant growth advanced and it was higher in rye before heading, but it was similar after heading compared to triticale. Cellulose and lignin contents of rye increased through 20 days after heading. However, in triticale cellulose increased until heading stage and it levelled off, but lignin content increased rapidly after heading. Among the crude fibers, only acid detergent fibers(ADF) was negatively correlated with in vitro dry matter digestibility(IVDMD) in both rye and triticale. IVDMD of rye decreased rapidly after heading, but it was maintained as high as heading stage up to 15 days after heading in triticale. Protein content and IVDMD in leaf blades were higher than those of culm + leaf sheath, hemicellulose was similar, and cellulose, lignin, and ADF in leaf blades were lower compared to culm + leaf sheath. In the early and middle part of April rye was superior to triticale as a soiling crop because of a better plant growth of rye under the low temperature conditions, but in the later part of April and early part of May triticale was superior to rye because of a rapid decreased in IVDMD of rye after heading and a late maturing characteristics of triticale. Planting both rye and triticale could prolong the utilization period of the soiling crops and increase in yield with better quality compared to a single crop of rye or triticale.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.2
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• pp.177-181
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• 2011

This research was carried out to establish perfect-drainage time in order to stabilize rice yield and improve rice quality. Treatments of perfect-drainage were conducted 5 days interval during 25 days to 50 days after heading date in the field of Saemangeum Gyehwa, newly reclaimed land. Accumulated temperature after heading date in 2010 increased about $100^{\circ}C$ and precipitation amount decreased a little compared to normal year harvesting time. Average panicle number was 16.5 and spikelet per panicle was 88. Perfect drainage time treatment after 40~50 days was 3% higher in percent ripened grain and 0.6 g heavier in 1,000 grain weight than treatment after 25~35 days. There was no difference of rice yield between perfect drainage time treatment after 25 days and 30~35 days, but rice yield was 7~8% higher in treatment after 40~50 days than 25 days. Head rice ratio in treatment after 35 days was the highest and the sooner perfect drainage time, the lower protein content. Soil moisture negatively correlated with soil hardness and EC in this result. With this results, we proposed that the time of perfect drainage in newly reclaimed land to stable rice production is 40~50 days after heading date.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.68 no.3
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• pp.106-113
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• 2023

We examined the heading responses of rice varieties over two years in Dandong, China to select the varieties that are adaptable to the bordering northwestern plains of North Korea. Dandong had slightly lower mean temperature than Sinuiju, North Korea but slightly higher than Supung, but it had almost the same day-length as the two regions in North Korea. In the two experimental years and two transplanting-date treatments, eight varieties (Jinbuol, Baegilmi, Joun, Jinok, Jopyeong, Jinbu, Sanhomi, and Odae) from South Korea and five varieties (Olbyeo2, Sonbong9, Onpo1, Gilju1, and Pyongdo5) from North Korea reached the heading stage not later than the latest heading dates of Dandong domestic varieties and the safe marginal heading dates of Dandong. We examined the basic vegetative phase (BVP), photoperiod-sensitivity (PS), and thermo-sensitivity (TS) of rice heading in a phytotron study to characterize the heading ecotypes of rice varieties adaptable to Dandong. For the rice varieties grown in Dandong experimental field, number of days to the heading stage was highly positively correlated with PS and, except middle and mid-late maturing three varieties, it was significantly positively correlated with BVP. Two-dimensional distribution plotting revealed that both 35 days or less BVP and 25 days or less PS were the characteristic heading ecotypes of the rice varieties adaptable to Dandong.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.6
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• pp.402-408
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• 2002

Rice cultivar 'Janganbyeo' was cultivated by irrigating the saline waters of high salinity (3.0%) and medium saliniy (1.5%) for 4 days, and low salinity (0.5%) for 30 days at tillering, early meiosis and heading stage. Leaf injury due to salinity was most severe at tillering stage in 1999, but at heading stage in 2000. Heading date was delayed by 1 to 5 days by treatment of saline waters only at tillering stage. Culm length and panicle length were most severely shortened by treatment at early meiosis stage. Yield and yield components except for panicle number were decreased most by high salinity treatment regardless of growth stages. In particular, ripening ratio and grain weight among the yield components were decreased most conspicuously by the saline water treatment regardless of salinity and growth stage. Regarding grain weight grain-filling rate and duration, there is no remarked difference among the concentrations and treatment durations of saline water at tillering stage. However, their reductions were very different among the concentrations and treatment durations of saline water at early meiosis stage, being greatest when treated with high salinity for 4 days and followed by low salinity for 30 days. Also their reductions were very severe only when treated with high salinity for 4 days at heading stage.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.4
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• pp.284-295
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• 2018

The safe and late marginal heading dates (SMHD, LMHD), cropping probability, and growth duration of rice were assessed using temperature data in the 27 regions of North Korea. The medians of SMHD and LMHD ranged Jul. 16 and Jul. 27 in Hyesan to Aug. 18 and Aug. 28 in Haeju, respectively, except Changjin, Pungsan, and Samjiyon that did not show any of the SMHD and LMHD. The medians of the days from early marginal transplanting date (EMTD) to heading date ranged 51 days in Hyesan to 109 days in Pyongyang for SMHD and those were delayed by 9~15 days for LMHD, compared to SMHD. Nineteen regions (Kaesong, Haeju, Yongyon, Singye, Sariwon, Nampo, Pyongyang, Anju, Kusong, Sinuiju, Changjon, Wonsan, Hamhung, Pyonggang, Yangdok, Huichon, Supung, Sinpo, Kanggye) and additional four regions (Kimchaek, Chongjin, Sonbong, Chunggang) had the rice cropping probability higher than 80% when analyzed based on the SMHD and LMHD, respectively. The representative SMHD ranged Jul. 24 for Pyonggang to Aug. 12 for Haeju. Compared to the days from EMTD to SMHD, those from EMTD to LMHD were delayed by 9~17 days. When applied SMHD, thirteen regions (Yangdok, Kanggye, Huichon, Supung, Yongyon, Kusong, Anju, Sinuiju, Singye, Pyongyang, Kaesong, Nampo, Sariwon) had the appropriate range of cumulative temperature during grain filling (CT) for grain yield and quality. Sinpo, Hamhung, Pyonggang, Wonsan, Changjon, and Haeju had the CT higher than $1,300^{\circ}C$. It is supposed that rice cropping could be extended to the regions where LMHD-applied cropping probability was higher than 80%. Delaying the heading date than SMHD could be also considered in the regions where the days to SMHD is small but CT is large.

• Korean Journal of Environmental Agriculture
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• v.13 no.3
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• pp.251-261
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• 1994

This study was conducted to get some basic information about rice plant development rate and heading ecology in various climatic conditions, growing nine varieties at three locations, Jinbu as the mountainous cool area, Suweon and Iri as the plain area for two years from 1987 to 1988. Average daily air temperature and day length from transplanting to heading date were analyzed in relation to the heading. Heading date and development rate of each variety were estimated by the Symplex method and the fitness of the model was evaluated. The results obtained as follows: Average daily air temperatures among varieties during the period from transplanting to heading ranged from 18 to $19^{\circ}C$ in Jinbu, from 22.5 to $23.5^{\circ}C$ in Suweon, and from 23.5 to $24.5^{\circ}C$ in Iri, the late-maturing varieties requiring the higher temperatures. The average heading days were about 20 days longer in Jinbu and $3{\sim}5$ days shorter in Iri than those in Suweon in all varieties. Little differences in accumulated temperature from transplanting to heading were observed in regions and years, and also among varieties. Developmental stages could be expressed as the accumulation of daily development rate and the predicted heading dates by the Symplex method were similar to the observed ones. The development rate of each variety varies with air temperatures. The early maturing Japonica types including the Unbong variety were fast in development rate at lower temperatures, but the late-maturing varieties of the Japonica type were late. A model to predict the heading dates of rice varieties by the Symplex method using air temperatures and day lengths was feasible.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.6
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• pp.487-498
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• 1992

To study the effects of different nursing methods and transplanting on the growth of rice plant (Oriza sativa L.) in southern region of Korea, Kumo-byeo, Palgong-byeo and Dongjinbyeo were transplanted from April 20 to July 20 at an interval of 15 days with 8 days old seedling (infant seedling) and 25 days old box-seedling for machine transplanting, and 45 days old conventional seedling. Threshold transplanting date in southern region of Korea were June 26 for 8 days old seedling, July 1 for 25 days old seedling and] July 11 for 45 days old seedling for Kumo-byeo, and June 21, June 30, July 10 for Palgong-byeo, June 10, June 24, July 5 for Dongjin-byeo, respectively. Yield has no uniform tendency according to the transplanting date. However, yield were greater in the order of 8 days old seedling >25 days old seedling> 45 days old seedling in Kuma-byeo and 25 days old seedling (equation omitted)8 days old seedling (equation omitted)45 days old seedling in Palgong-byeo, 45 days old seedling(equation omitted)25 days old seedling(equation omitted) 8 days old seedling in Dongjin-byeo. The optimum accumulated air temperature during yield productive stage around heading (40 days from 10 days before heading to 30 days after heading) for high yield were 1,003$^{\circ}C$ for 8 days old seedling, 1,014$^{\circ}C$ for 25 days old seedling and 1,027$^{\circ}C$ for 45 days old seedling in Kumo-byeo. And they were 1,018$^{\circ}C$, 1,015$^{\circ}C$, 1,086$^{\circ}C$ in Palgong-byeo and 998$^{\circ}C$, 984$^{\circ}C$, 949$^{\circ}C$ in Dongjin-byeo, respectively. Earlier transplanting with 8 days old seedling showed higher ratio of broken rice and green kerneled rice in Kuma-byeo, and late transplanting after July 5 showed significant high rate of green kerneled rice. Palgong-byeo and Dongjin-byeo also showed high rate of green kerneled rice at transplanting after July 5.

• Journal of The Korean Society of Grassland and Forage Science
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• v.32 no.3
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• pp.285-292
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• 2012

This experiment was carried out to determine the harvesting day after heading of barley for highest total forage yield in double cropping with corn at paddy field in middle region. The fresh barley yield was the highest at the harvest of 20 days after heading, but the dry matter yield and TDN yield were the highest at the harvest of 25 days after heading because of higher dry matter rate. The dry matter yield of corn after the harvest of 25 days after heading was decreased about 16 percent than that of the check, sowing on april 25. But total fresh yield of corn monoculture was lower about 31 percent, and decreased 28 percent of dry matter and 23 percent of TDN yield, respectively, than that of the double cropping system with corn and barley. In double cropping system at paddy field, the total forage yield was the highest at the harvest of 25 days after heading of barley and grew corn subsequently. Although yield of corn was reduced by late sowing, the total forage yield was increased by double cropping system compared with corn monoculture.

• Korean Journal of Agricultural Science
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• v.9 no.1
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• pp.231-238
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• 1982

The study was done to determine the proper transplanting dates and seedling ages of rice when mechanical transplanting was attempted. Heading dates of the Milyang #23, developed from Tong-il rice was delayed by delayed transplanting and the percent of filling grain was also low. The proper heading dates for the variety should be the first part of August and the transplanting should be done by the end of May. The presumed last days for the transplantation was considered early part of June. 30 to 40 days old seedlings were very effective to have healthy rooting systems. However, the Milyang #15 had shown more tolerance to the late transplantation than Milyang #23 and the degree of delaying heading dates due to the delayed transplantation was rather smaller than that of the Milyang #23. Even when the Milyang #15 was transplanted on June 30, the heading dates were around the middle of August and the ripening percentage was comparatively high and yield was also high. Therefore, the proper heading dates of the Milyang #15 might be around the middle of August and transplanting dates should be the first part of June. The possible last dates of transplantation of the Milyang #15 was assumed to be the last days of June and the proper seedling ages would be 20 to 30 day after sowing.