• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.942-948
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• 2002

When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and the strength development may be delayed. One of the solution methods to resolve these problems is to reduce freezing temperature of concrete by the use of chemical admixture called Accelerator for freeze protection. In this study we Investigate the effect on the strength development of cement mortar using accelerator for freeze protection with the variable curing condition. As the result of this study, the mortar using accelerator for freeze protection show continuously the strength development in curing condition of -5$^{\circ}C$. And the compressive strength under variable temperature condition was higher than constant temperature condition in same maturity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.132-139
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• 2017

In this study, in order to prevent the frost damage of the concrete, the characteristics of the form using heating sheet utilizing the chemical reaction of quicklime and the insulation were evaluated through experiments at low temperature. In the case of form at $-10^{\circ}C$, the form with attached heating sheet showed a temperature history of more than $10^{\circ}C$ higher than that of wood form at the early of concreting due to heat of the quicklime in the heating sheet. In the case of the insulated form, the concrete was kept at a high temperature by preserving the hydration heat. When the heating sheet and the isopink(extruded polystyrene) were attached together on the form, the effect was the same as that of the vacuum insulation. The compressive strength of the form with vacuum insulation and form with isopink, heating sheet as measured about 5 MPa at age 3. The experimental in Mongolia, as with the pervious results, the form with the heating sheet and the insulation showed the highest temperature history over $25^{\circ}C$ for 48 hours. Therefore, it was confirmed that the heating sheet and insulation are attached to the form, which helps the concrete strength development at low temperature by heat generation and the insulation effect.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.59 no.4
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• pp.483-491
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• 2014

Double cropping system including paddy field soybean is widely adopted nationwide, due to rise in market price and its higher income than paddy field rice. Sowing date of soybean as a second crop is being delayed depending on first crop's growth period and harvesting time. Due to the increased temperature in October and delayed first frost date, soybean could be harvested without frost damage even in late-plating. Therefore, selection of soybean cultivar which is appropriate for this environment is very important. The effect of sowing date and genotype of soybean on growth and yield was investigated for three planting dates (June 20, July 5, and July 20) with ten cultivars developed for soy-pate production, to figure out plant development and yield pattern in delayed planting. As planting date is delayed, plant height and pod number was decreased and this pattern was more clearly detected in mid-late maturity cultivars. Hundred-seed weight did not show significant changes even in late planting, due to compensations between yield components. Yield reduction of July 20 in contrast to that of June 20 showed that Nampung (9.6%) showed the least yield decline. Maximum yield was achieved from Daepung, Taekwang, and Uram among other soybean cultivars in late planting. Shortening of growth period was strongly detected in reproductive stage while length of vegetative stage was regularly maintained in both early and mid-late maturity cultivars.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.2
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• pp.149-154
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• 1992

Buckwheat has been a popular favorite food crop in Korea for a long time. The objective of the study was to investigate the effects of climatic conditions and cultural methods on grain yields of summer buckwheat variety Sinnong 1 planted during the spring season in Suwon, Korea from 1989 to 1991. Frost minimum temperature of late April was -0.3$^{\circ}C$ in 1990 being very low as compared with 3.7$^{\circ}C$ of the normal year, and affected early growth of the seedlings emerging from the soil surface. In late May of 1990, the frost minimum temperature was 7.3$^{\circ}C$ being low as compared with 8.8$^{\circ}C$ of the normal year, and also induced cold injury to fertilization and grain filling. Total precipitation 374.5mm of mid and late June, 1990 provided serious damage to the grain filling and maturing buckwheat seeds and along with causing seed sprouting before harvest. However, the climates of 1989 and 1991 were very good for the growth and development of spring-sown buckwheats. When summer buckwheat cultivar Sinnong 1 was planted on April 20, 1989, its highest grain yields 268-292kg /10a were harvested from the plots of seeding rate 8kg /10a, drill seeding and polyethylene film mulching, and the mean grain yield of the plots was 238kg /10a in 1989, but 64.3kg in Suwon, and 40.2kg /10a in Muan in 1990. In 1991 maximum grain yield 277kg /10a was produced from the April 15 planted and vinyl-mulched plot, and 255kg /10a from the April 25 planted and non-mulched plot. Herbicide Alachlor-sprayed plots produced lower grain yields than no weed control and manual weeding plots. Mechanized drill-seeding saved 83～84% in planting hours as compared with manual broadcasting 21.6 hours /ha, and produced 9% more in grain yields from the two-season croppings of mechanized drill-seeding culture being 364kg /10a in total yields per year.

• Journal of The Korean Society of Grassland and Forage Science
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• v.33 no.2
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• pp.87-93
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• 2013

'Okhan' (Avena sativa L.), an oat cultivar for winter use, was developed by the breeding team at the Department of Rice and Winter Cereal Crop, NICS, RDA in 2011. It was derived from an original cross between 'Early80', exhibiting early heading, and 'Maine PI-590' (CI 7518), exhibiting large-size grain, in 1995. Subsequent generations as well as cross-bred cultivars were handled in bulk, and pedigree selection programs took place at Suwon and Yeoncheon, respectively. A promising line, 'SO95027-B-45-16-10-6-2-Y7-10', was selected in 2004, and was designated 'Gwiri74' after being selected from a yield trial for three years from 2005 to 2008. The breeding line 'Gwiri74' was subsequently evaluated for earliness of heading and forage yield in four different locations, Yesan, Iksan, Kimjae, and Jeju, from 2009 to 2011, and was finally named as 'Okhan'. Over 3 years, the heading date of 'Okhan' was about 6 days earlier than that of the check cultivar 'Samhan', and their average forage dry matter yield harvested at the milk-ripe stage was 15.0 ton $ha^{-1}$, compared with 14.1 ton $ha^{-1}$ of check cultivar. Cultivar 'Okhan' was lower than the check cultivar 'Samhan' in terms of the protein content (9.2% and 9.9%, respectively) and total digestible nutrients (58.5%, and 59.3%, respectively), while the TDN yield per ha was more than the check (8.70 and 8.36 kg, respectively). Fall sowing cropping of 'Okhan' is recommended only in areas where average daily minimum mean temperatures in January are higher than $-7^{\circ}C$, and it should not be cultivated in mountain areas, where frost damage is likely to occur.

• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.1
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• pp.1-9
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• 2006

Regardless of the recent observed warmer winters in Korea, more freeze injuries and associated economic losses are reported in fruit industry than ever before. Existing freeze-frost forecasting systems employ only daily minimum temperature for judging the potential damage on dormant flowering buds but cannot accommodate potential biological responses such as short-term acclimation of plants to severe weather episodes as well as annual variation in climate. We introduce 'dormancy depth', in addition to daily minimum temperature, as a complementary criterion for judging the potential damage of freezing temperatures on dormant flowering buds of grape vines. Dormancy depth can be estimated by a phonology model driven by daily maximum and minimum temperature and is expected to make a reasonable proxy for physiological tolerance of buds to low temperature. Dormancy depth at a selected site was estimated for a climatological normal year by this model, and we found a close similarity in time course change pattern between the estimated dormancy depth and the known cold tolerance of fruit trees. Inter-annual and spatial variation in dormancy depth were identified by this method, showing the feasibility of using dormancy depth as a proxy indicator for tolerance to low temperature during the winter season. The model was applied to 10 vineyards which were recently damaged by a cold spell, and a temperature-dormancy depth-freeze injury relationship was formulated into an exponential-saturation model which can be used for judging freeze risk under a given set of temperature and dormancy depth. Based on this model and the expected lowest temperature with a 10-year recurrence interval, a freeze risk probability map was produced for Hwaseong County, Korea. The results seemed to explain why the vineyards in the warmer part of Hwaseong County have been hit by more freeBe damage than those in the cooler part of the county. A dormancy depth-minimum temperature dual engine freeze warning system was designed for vineyards in major production counties in Korea by combining the site-specific dormancy depth and minimum temperature forecasts with the freeze risk model. In this system, daily accumulation of thermal time since last fall leads to the dormancy state (depth) for today. The regional minimum temperature forecast for tomorrow by the Korea Meteorological Administration is converted to the site specific forecast at a 30m resolution. These data are input to the freeze risk model and the percent damage probability is calculated for each grid cell and mapped for the entire county. Similar approaches may be used to develop freeze warning systems for other deciduous fruit trees.

• Korean Journal of Breeding Science
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• v.40 no.4
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• pp.512-516
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• 2008

A new naked oat cultivar 'Choyang' (Avena sativa L.) was developed by the breeding team at the Department of Rice and Winter Cereal Crop, NICS, RDA in 2007. It was derived from a cross between 'Sikyonggwiri' and 'Gwiri23'. The cultivar, Sikyonggwiri is early heading while the breeding line Gwiri23 has a high yielding potential with large-size grain. Bulk method combined with pedigree selection program was employed in subsequent generations, and the promising line SO96025-B-303-44-2-5 was selected for agronomic performance in 2002. The line showed both high yield and good husking rate of seed in the Yield Trial tested at Suwon in 2003 to 2004, and was subsequently designated as 'Gwiri57'. Gwiri57 was evaluated for winter hardiness, earliness, and yield in four locations, Gimje, Iksan, Jeongeup and Jinju from 2005 to 2007 and was released as Choyang. Choyang headed 11 days earlier and matured 5 days earlier than the check cultivar 'Sunyang' in the paddy field condition. The new cultivar Choyang had 97 cm of culm length and 23.4 cm of spike length, 658 spikes per $m^2$, 75 grains per spike, 28.8 g of 1,000-grain weight, and 636 g of test weight. Choyang showed better winter hardiness than that of the check cultivar Sunyang, and similar seed quality to the check cultivar in respect to crude protein (12.9%) and ${\beta}$-glucan content (4.7%). However, it showed higher husking rate than the check cultivar. The grain yield of Choyang in the regional yield trial for 3 consecutive years was averaged $4.67MT\;ha^{-1}$, which was 38% higher than that of the check cultivar Sunyang. Choyang is recommended for the fall sowing cropping only in the southern area where daily minimum mean temperatures are averaged higher than $-4^{\circ}C$ in January, and is not recommended the in mountain area where frost damage is presumable.

• Journal of The Korean Society of Grassland and Forage Science
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• v.33 no.4
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• pp.227-233
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• 2013

'Taehan' (Avena sativa L.), a winter oat for forage use, was developed by the breeding team at the Department of Rice and Winter Cereal Crops, NICS, RDA in 2012. It was derived from a cross between 'Malgwiri' and 'CI8015'. Subsequent generations were handled in bulk and pedigree selection programs at Suwon and Yeoncheon, respectively. After 2 years of preliminary and advanced yield tests, 'SO00020B-YB-15-5-9-4-3', designated as 'Gwiri78', were subsequently evaluated for earliness and forage yield during 3 years in four regions such as Yesan, Iksan-1 (Paddy), Iksan-2 (upland), and Jeju from 2010 to 2012, and finally named 'Taehan'. Over 3 years, the heading date of 'Taehan' was about 6 days earlier than that of the check cultivar 'Samhan' (May 8 and May 14, respectively), and their average forage dry matter yield harvested at the milk-ripe stage was 14.5 tone $ha^{-1}$, compared with 14.1 tone $ha^{-1}$ for the check cultivar. The cultivar 'Taehan' was lower than that of the check cultivar 'Samhan' in terms of protein content (6.3% and 7.7%, respectively) and total digestible nutrients (60.7%, and 62.1%, respectively). The TDN yield was more than that of the check cultivar (9.1 tone $ha^{-1}$ and 8.0 tone $ha^{-1}$, respectively). Fall cropping of 'Taehan' is recommended only in areas where average daily minimum mean temperatures in January are > $-6^{\circ}C$, and it should not be cultivated in mountainous areas, where frost damage is likely to occur.

• Korean Journal of Breeding Science
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• v.41 no.1
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• pp.56-60
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• 2009

A new naked oat cultivar Daeyang (Avena sativa L.) was developed by Department of Rice and Winter Cereal Crop, NICS, RDA in 2007. It was derived from a cross between 'FLX446-1-84-Q1'. and 'SO92004-B-3-3-5-7'. The FLX446-1-84-Q1, a naked oat cultivar from USA, is early heading and has good seed quality, while the SO92004-B-3-3-5-7, a covered oat breeding line, has a high yield with large grain. Subsequent generations were handled in a bulk method and pedigree selection program, and the SO97013-B-16-4 was selected based on agronomic performance in 2001. The line showed both high yield and good husking rate of seed in the yield trial tested at Suwon from 2002 to 2003, being designated as Gwiri51. The Gwiri51 was subsequently evaluated for winter hardiness, earliness, and yield in four locations, Gimje, Iksan, Jeongeup, and Jinju, from 2004 to 2007 and was designated as "Daeyang" and released. Its heading date was May 8 and maturing time was June 14 in a paddy field condition. The new cultivar Daeyang had 97 cm of culm length and 25.2 cm of spike length, 644 spikes per $m^2$, 65 grains per spike, 30.3 g of 1,000-grain weight, and 635 g of test weight. Daeyang showed better winter hardiness than that of the check cultivar 'Sunyang', and similar seed quality to the check cultivar in respect to percent content crude protein and $\beta$-glucan. However, it showed higher husking rate than the check cultivar. Grain yield of Daeyang in the regional yield trial for 4 years were averaged 4.18 MT $ha^{-1}$, which was 20% higher than that of the check cultivar Sunyang. Fall sowing cropping is recommended only in a south area where daily minimum mean temperatures are averaged higher than $-4^{\circ}C$ in January, and should be excluded in mountain area where frost damage is presumable.