• Journal of Radiation Protection and Research
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• v.23 no.1
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• pp.25-32
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• 1998

Tritium is released into the environment as various form but HTO is most relevant to the incorporation of tritium into living organisms and to the formation of OBT. Tritiated compounds may be transported to humans via several tropic levels. Retention times of organically bound tritium in organisms are considerably longer than those of tritiated water, which has significant consequences on exposure dose estimation. It is rather difficult to predict the amount of OBT produced by the photosynthetic process of plants because it may be influenced by a multitude of environmental factors and plant parameters. Tritiated organic matters are classified as the exchangeable or nonexchangeable bound tritium according to the bound form. After short term HTO exposure in plants, the formation and uptake of OBT were evaluated.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.45-50
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• 2005

This study was conducted to measure and understand the exchange of CO₂ and water in a rice canopy. Eddy covariance system was installed on a 10m tower along with other meteorological instruments. CO₂ flux and surface energy balance were measured throughout the whole growing season in 2003 over a typical paddy field in Icheon, Korea. During the early growth stage in May and June, most of net radiation was partitioned to latent heat flux with daytime Bowen ratio of 0.3 to 0.7. Evapotranspiration (i.e., daily integrated latent heat flux) typically ranged from 3 to 4 mm d/sup -1/, with even higher rates on sunny days. Daily integrated net ecosystem exchange (NEE) of CO₂ increased with increasing solar radiation and leaf area index (LAI). The NEE was especially high during the stages of young panicle formation and heading. On 1 June 2003, when the rice field was flooded, it was a weak sink of atmospheric CO₂ with an uptake rate of 9.1 gm/sup -2/d/sup -1/. Despite frequent rainy and cloudy conditions in summer, maximum NEE of 36.2 gm/sup -2/d/sup -1/ occurred on 31 July prior to heading stage. As rice crop senesced after early September, the NEE decreased.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.4
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• pp.215-219
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• 2001

Land surface parameterization schemes for atmospheric models as well as decision support tools for ecosystem management require a frequent updating of land cover classification data for regional to global scales. Rice paddies have not been treated independently from other agricultural land classes in many classification systems, despite their atmospheric and ecological significance. A simple but improved method over conventional land cover classification schemes for rice paddy is suggested. Normalized difference vegetation index (NDVI) was calculated for the land area of South Korea at a 1km by 1 km resolution from the visible and the near-infrared channel reflectances of NOAA-AVHRR (Advanced Very High Resolution Radiometer). Monthly composite images of daily maximum NDVI were prepared for May and August, and used to classify 4 major land cover classes : urban, farmland, forests and water body. Among the pixels classified as "forests" in August, those classified as "water body" in May were assigned a "rice paddy" class. The distribution pattern of "rice paddy" pixels was very similar to the reported rice acreage of 1,455 Myons, which is the smallest administrative land unit in Korea. The correlation coefficient between the estimated and the reported acreage of Myons was 0.7, while 0.5 was calculated from the USGS classification.calculated from the USGS classification.

• Korean Journal of Environmental Agriculture
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• v.2 no.2
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• pp.108-113
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• 1983

There has been two kind of research fields in evaluating the ecotoxicity of chemicals The one is a bioassay and the other is an ecosystem analysis. The toxicants are transported into different biota, which have quite different environmental behaviour patterns and toxic properties. The effects of pesticides (butachlor, carbofuran, and tricyclazole) on periphyton community was studied by analyzing content of chlorophyll-a and autotrophic index (AI) that is a means of determining the trophic nature of the periphyton community. Results indicated that the content of chlorophyll-a was not influenced by the pesticides. The growth of algae was inhibited by sunshine period. And AI value is 43-2027: the large value indicates heterotrophic periphyton community, and was not affected by pesticides.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.1
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• pp.57-72
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• 2018

Time series analysis of tower flux measurement can be used to build quantitative evidence for the achievement of climate-smart agriculture (CSA). In this study, we have assessed the first objective of CSA (regarding ecosystem productivity and efficiency) for rice paddy-dominated heterogeneous farmland. A set of quantitative indicators were evaluated by analysing the time series data of carbon, water and energy fluxes over the Haenam farmland site in Korea (HFK) during the rice growing seasons from 2003 to 2015. Four different varieties of rice were cultivated during the study period in chronological order of Dongjin No. 1 (2003-2008), Nampyung (2009), Onnuri (2010-2011), and Saenuri (2012-2015). Overall at HFK, gross primary productivity (GPP) ranged from 800 to $944g\;C\;m^{-2}$, water use efficiency (WUE) ranged from 1.91 to $2.80g\;C\;kg\;H_2O^{-1}$, carbon uptake efficiency (CUE) ranged from 1.06 to 1.34, and light use efficiency (LUE) ranged from 0.99 to $1.55g\;C\;MJ^{-1}$. Among the four rice varieties, Dongjin No. 1-dominated HFK showed the highest productivity with higher WUE and LUE, but comparable CUE. Considering the heterogeneous vegetation cover at HFK, a rule of thumb comparison suggested that the productivity of Dongjin No1-dominated HFK was comparable to those of monoculture rice paddies in Asia, whereas HFK was more efficient in water use and less efficient in carbon uptake. Saenuri-dominated HFK also produced high productivity but with the growing season length longer than Dongjin No.1. Although the latter showed better traits for CSA, farmers cultivate Saenuri because of higher pest resistance (associated with adaptability and resilience). This emphasizes the need for the evaluation of other two objectives of CSA (i.e. system resilience and greenhouse gas mitigation) for complete assessment at HFK, which is currently in progress.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.666-672
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• 1997

Twenty years' daily mean air temperature data was used to calculate the critical early seeding date(CESD), the optimum heading date(OHD), the critical late heading date for stable ripening(CHDR) and the critical late ripening date(CLRD) for rice seeded on dry paddy in different agroclimatic zones in Korea. The CESD was defined as the first day with mean air temperature of 13$^{\circ}C$, and the OHD as the first day of the 40 consecutive days with mean air temperature of 22$^{\circ}C$ or above after heading. The CHDR was defined as the date after which the cumulative daily mean air temperature would be at least 76$0^{\circ}C$. Lastly, the CLRD was defined as the last day when daily mean air temperature remains above 15$^{\circ}C$. This information was used for the estimation of periods from the earliest date of seeding to optimum heading date, the latest possible date of heading and the latest possible date of ripening in respective regions. For instance, in Suwon, those respective periods mentioned were found to be 104days, 124days, and 165days.

• Korean journal of applied entomology
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• v.21 no.1 s.50
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• pp.38-48
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• 1982

This study was conducted to investigate the changes in moth occurrence of striped rice barer, Chilo suppressalis (Walker), in relation to climatic factors, rice varieties, and cultural practices. The light trap data from 41 forecasting stations for 14 years from 1966 to 1979 were analyzed by means of the changes in the time and amount of borer occurrence in connection with the introduction of new rice varieties, the accumulated effective day-degree and its variation for completing one generation, and the climatic factors affecting the moth occurrence. The total number of moths caught by light traps in both spring and summer generations were considerably decreased with the wide cultivation of new rice varieties. In fact, the spring moths were remarkably decreased since the new varieties were introduced in 1972. The occurrence ratio of summer moths against the preceeding spring moths was higher in the middle region and middle southern mountainous area than the other regions. Its high ratio of regions was annually expanded from the middle region to the southern region. The $50\%$ emergence dates of both generations were later in the southeastern region than in the middle region. The ecological characteristics were clearly shown between the northern and southern region of Chupungryeong in terms of the occurrence of summer moths, the ratio of occurrence of summer moths to the preceeding spring moths, and $50\%$ emergence dates of the summer moths during the years of $1977\~1979$. The ratio of the summer moth occurrence to the preceeding generation was negatively correlated with the average temperature in lune and July, respectively, and the average precipitation in late June. The ratio of spring moth occurrence over the preceeding generation was positively correlated with the average temperature in September, October, November, and March, respectively, whereas it was negatively correlated with the average precipitation in early September and March, and the average humidity in early May. The effective day-degree for one generation was in the range from 600 to 900 DD at upper threshold $30^{\circ}C$ and lower threshold $10^{\circ}C$.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.1
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• pp.65-73
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• 2008

Because main barley straw management is changing these days from off-fields to burning that may relate to air quality concerning the global warming, this study was conducted to investigate the effects of barley-straw management practices on greenhouse gas emissions during rice cultivation in rice-barley double cropping system. The treatments were barley straw burning, off-field usage of barley straw and incorporation of barley straw in paddy fields. Laboratory experiment showed that burning of barley straw at the rate of $4.5Mg\;ha^{-1}$ emitted GHGs in the amounts of 4,607, 19.5, and $0.9kg\;ha^{-1}$ of $CO_2$, $CH_4$, and $N_2O$, respectively. During the rice cultivation of the rice-barley double cropping system, the highest GHG emission by evaluated close-static chamber method was observed from the soil incorporation of barley straw with 387 and $1.0kg\;ha^{-1}$ of $CH_4$ and $N_2O$, respectively. The GHGs emissions from the barley straw burning and off-field usage treatments were 233 and $160kg\;ha^{-1}$ for $CH_4$ and 0.80 and $0.79kg\;ha^{-1}$ for $N_2O$, respectively. The barley straw burning treatment showed the greatest GHGs emission among barley straw management practices in rice-barley double cropping system when considering GHGs emissions both during burning and from paddy fields during the cropping seasons. As a result, the GHGs emissions recorded in the barley straw incorporation to soil and off-field usage treatments were 22.4 and 66.8%, respectively, less than sum of GHGs emissions from the burning of barley straw and from paddy fields during rice cultivation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.3
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• pp.261-272
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• 2008

This study was conducted to provide the fundamental data based on the agronomic characteristics of domestic aroma rice, widely cultivated domestic rice and foreign aroma rice for breeding of functional aromatic rice. Among the 104 varieties, all of domestic aroma rice and widely cultivated rice varieties were headed, 24 of 84 varieties of foreign aroma rice were not headed. The average heading date of domestic aroma rice Japonica types of domestic rice was later as 136 day, and Tongil types of domestic aroma rice were faster as 122 day. The average culm length of Indica types of foreign aroma rice was longer as 130 cm, and Tongil types of were shorter as 74 cm. The average panicle length of domestic aroma rice and traditional rice were about 21 cm, and Indica types of foreign aroma rice were longer as 29.5 cm. The average 1,000 grain weight of Tongil types of domestic aroma rice and was not a difference with the domestic aroma rice and was more 2.5 g than the Indica types of foreign aroma rice. The average ratio of grain width and length of Indica types of foreign aroma rice were highest as 3.29 (W/L), and the domestic traditional rice was lowest as 1.7 (W/L). The average fertility rate of the domestic aroma rice, the widely cultivated domestic rice, and the Japonica types of foreign aroma rice were above 89.7%, but the Indica types of foreign and the Tongil types of domestic aroma rice were below 65.4%. The average germination rate of foreign aroma rice were above 83.7%, and domestic aroma rice were above 90.4%. The non-glutinous rice were 64 varieties (84.2%) of total 104 accessions of material rice and the waxy rice were 7 varieties (1%). In the domestic aroma rice, Hyangmi2ho and Aranghyangchalbyeo has a mild aroma grade. In the foreign aroma rice, 22 of 40 varieties of Indica types and 9 of 16 varieties of Japonica types has a lightly aroma grade. And 13 varieties of widely cultivated domestic rice has a non-aroma grade.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.2
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• pp.203-216
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• 2008

This study was conducted to provide the fundamental data based on the analysis of phsyco-chemical characteristics of domestic aroma rice and foreign aroma rice for breeding of aroma rice. The average amylose content of domestic aroma rice and widely cultured domestic traditional rice were 18.1% and 19.0% respectively. The Indica and the Japonica types were 25.6% and 25.0%. In the domestic rice of Tongil and Japonica type, the average protein content were 7.6% and 6.4% respectively. And the average protein content of foreign Indica and Japonica type were 7.6% and 7.0% respectively. And the average protein content of widely cultured domestic traditional rice was 5.6%. The Japonica type of rice shown a low protein content compared with Indica type of rice, and the foreign Indica types of rice exhibited a wide range of protein contents. The average alkali digestive value (ADV) of Tongil type of the domestic aroma rice was about 5.0 and the value of Japonica type was about 6.0. The average ADV of foreign Indica and Japonica type were 4.3 and 5.1 respectively. Also the average ADV of widely cultured domestic aroma rice was about 6.0. The foreign aroma rice were distributed a variable range of ADV value and lower than the both domestic aroma rice and widely cultivated domestic rice. In the whole aspect of the amylogram, the highest viscosity, the lowest viscosity and the last viscosity of the total resources, in domestic aroma rice were clearly lower with the next order, Japonica type of foreign aroma rice, Indica type of foreign aroma rice, Japonica type of domestic aroma rice, widely cultured domestic traditional rice, and Tongil type of domestic aroma rice. It shown the difference aspect of amylograms according to the eco-type of the domestic and foreign aroma and the general rice, and it was distinguishable in difference of the aspect of the amylogram of the endosperm of rice as non-glutinous rice, waxy rice, and middle-waxy rice.