• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.254-258
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• 1998

Distribution and occurrence of weedy rice in Kyonggi region were surveyed in 1996. Weedy rice was observed in 1368 fields (54.9%) of total 2490 fields. Almost two thirds of paddy fields in northern mountainous region were contaminated by weedy rice and more severe contamination, three forths of paddy fields, was observed in suburban regions. In those regions, occurrence of weedy rice was greater than those in north-eastern inland and south-western plain regions. The occurrence of weedy rice was higher in water seeding cultivation (66.7%) than other cultivation methods. The number of weedy rice per 10a was 756.7 plants in direct seeding on dry paddy and 379.4 plants in water seeding. The occurrence of weedy rice was higher in fields planted by farmer's seeds than that of paddy fields cultivated by certified seeds, and the longer the farmer's seeds being used, the more weedy rice occurred in paddy field.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.3
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• pp.5-11
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• 1978

Since 1970, herbicides have been widely used in the crop production, especially in paddy field in Korea. In 1978, both preemergence and postemergence type herbicides are applied in the approximately 70% of total paddy field and 15% of upland to control weeds. Most herbicides control annual weeds effectively, but perennials have been problems in the paddy field. Under upland conditions, effectiveness of herbicides varies depending on many environmental conditions (soil moisture, soil physical properties, temperature, etc.) as well as uniform application of appropriate amounts of herbicides. In Korea, many research works have been concentrated on the screening of new herbicides in terms of herbicide effectiveness and yield or phytotoxicity of crops, and especially on the paddy field. However, physiological aspects of herbicidal action in plant and interaction of herbicides with the environments have not been studied approximately. Therefore, researches on the uptake of herbicides and the influence of herbicides on the physiological phenomena such as photosynthesis, respiration, nutrient uptake etc., to control troublesome perennial weeds in the paddy field are needed in future. Also some researches are needed to improve effectiveness of herbicirdes under upland conditions.

• Korean Journal of Environment and Ecology
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• v.17 no.1
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• pp.44-55
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• 2003

The wetland in the city could be mainly divided into the deep water type and the abandoned paddy type, so this study was conducted to analyze characteristics between the two types of the wetland. The former sample site was located near the Olympic village in Songpa-gu of Seoul, and the latter sample site was in front of the Mt. Bukhan fortress in Eunpyeong-gu of Seoul. The actual vegetation, vascular plants, and avian fauna were researched. In the actual vegetation, the deep water type had the broad surface of water and the emerged plant as Phragmites communis have grown widely, but the abandoned paddy type had the narrow sur-face of water and hydrophyte as Persicaria thunbergii have grown widely. It might be judged because the water depth of the abandoned paddy type were shallow wholly. And the floating-leaved plants and the free-floating planktonic plants were not observed such as Nymphaea tetragona var. angusta, Lemna paucicostata in the abandoned paddy type wetland. The wild birds were mainly observed at the edge of the wetland(at the edge of woodland) in the abandoned paddy type, but were observed equally in the deep water type. 28 families 433 species were observed at the former site and 32 families 365 species were observed at latter site. It was judged that the various topographical structure(habitat diversity) might make all items various.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.926-936
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• 1996

Field hulling of high-moisture paddy followed by brown rice drying offers many advantages over the present paddy harvesting and drying offers many advantages over the present paddy harvesting and drying system. We did a preliminary study of the parameters for efficient hulling of high-moisture paddy using the IRRI Centrifugal Huller and two India rice varieties. Hulling capacity , hulling efficiency , brown rice recovery and percent whole bown rice were generally best at the impeller peripheral speed of 44m/s. A second pass through the huller increased hulling capacity , brown rice revery and hulling efficiency, but reduced percent whole brown rice. To solve this , we recommed separation of paddy after hulling and aspiration such that only unhulled and partially -hulled grains will be fed back to the huller. Paddy at even 23% m.c. could be effectively hulled by the impeller-type huller , but the results were generally better at 14 to 17% m.c. Only in percent whole brown rice did the 17 to 23% m.c. range performed better than that of 14% m.c. Difference invarietal response to hulling was observed.

• Journal of Biosystems Engineering
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• v.24 no.3
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• pp.195-208
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• 1999

A computer simulation was carried out to investigate draft characteristics of Korean paddy field for obtaining the basic reference to the selection of optimum moldboard type suitable for Korean paddy field conditions. Cylindrical, cylindroidal, semihelical moldboard plows, and one type of oriental Janggi were used for simulation. A series of soil bin experiments was conducted to compare the experimental results with the predicted drafts from computer simulation using the cylindroidal moldboard plow. The computer model predicted draft force with 1~12% error at 12~16cm plowing depth which is the most conventional plowing depth in the rural area in Korea. Thus, the computer model was considered to be good enough for simulation. Due to the different plowing width of experimental plows, specific draft was selected for comparison by computer simulations. Specific draft of cylindrical moldboard plow was ranged from 3 to 6 N/$\textrm{cm}^2$ according to the soil conditions, plowing speed and plowing depth, 2.5~3.0 N/$\textrm{cm}^2$ for semihelical moldboard plow.

• Korean Journal of Environment and Ecology
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• v.27 no.2
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• pp.209-218
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• 2013

This study was conducted to analyze the characteristics of odonata communities as habitat types in Wonju City, Korea. The 33 plots were installed at 4 types of biotope like abandoned paddy fields, natural type reservoir, natural type river and forest valley in Wonju city. From the survey, the 9 family and 38 species were identified. As the result of comparative investigation of the species composition of each habitat through TWINSPAN analyzing, the difference of species composition was definite in abandoned paddy field, natural type reservoir and forest valley, however, it was uncertain in natural type river. The dominant species and the subdominant species of each habitat were mainly Sympetrum frequens and Sympetrum infuscatum but the distributions of Paracercion hieroglyphicum, Epophthalmia elegans, and Anax parthenope julius were different as haibtat types. The order of the index of species diversity was not different between abandoned paddy fiedls, natural type reservoir and natural type river, but forest valley was low. The abandoned paddy field was shown the most diverse spawning type of odonata, it is considered that hydrophyten play an important role in the abundant of odonata since the sorts of odonata spawning in plants are majority. As the result of analyzing interspecies relationship, Crocothemis servilia mariannae and Orthetrum albistylum, Crocothemis servilia mariannae-Platycnemis phyllopoda, Lyriothemis pachygastra-Sympetrum parvulum are shown the positive correlation, however, they have a difference in preferred habitat between high correlation species.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.1
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• pp.37-44
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• 1992

Germinability, electrophoretic variation of protein of shattered seeds during overwintering and characteristic of main agronomic traits of off-type rice plant occurring in paddy field harvested by combine were investigated. Germinability of shattered seed decreased as time goes in paddy field in both Japonica and Tongil type varieties. Electrophoretic protein bands become more and more light as time goes. Occurrence of off-type rice plant was higher in Japonica varieties than in Tongil type varieties. Off-type rice plant was shorter in plant height, leaf length, tiller number per hill, internode length, panicle length and spike let number per panicle. Germinability of seeds of off-type rice plant as not significantly different compared to the control variety. Yield of off-type plants of Japonica varieties was on average 5.1kg / 10a and that of Tongil type varieties was on average 0.9kg /10a. Mixing ratio to the control variety was about 0.7% in Japonica varieties and that of Tongil type varieties was about 0.1%.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.3
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• pp.170-175
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• 2001

This study was carried out to investigate the distribution and characteristics of off-type rice plant in farmer's paddy field. The ratio of the field contaminated by off-type rice was highest in the southwestern area, followed by the southeastern area, the central area in Korea. The occurrence density of off-type rice was higher in the southern area than the central area. The short-grain red rice was the most dominant off-type rice group, followed by extremely late and sterile rice group and long-grain red rice group in Korea. The long-grain red rice group was dominant in Jeonnam and Kyongnam, and the extremely late and sterile rice group was dominant in Jeonbuk, and the short-grain red rice group in the other provinces. The culm length of most off-type rice groups growing in the farmer's paddy fields was longer than the farmer's cultivars, and the long-grain red rice group and the short-grain red rice group were especially longer. The number of spikelets per panicle of the off-type rice groups were generally greater than the farmer's cultlvars, and in particular, the extremely late and sterile rice group and the long-grain normal rice group had more spikelet per panicle. Most of the off-type rice groups were extremely sterile.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.2
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• pp.132-139
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• 2010

To manage the effluent nutrients amounts from rice paddy fields using free range ducks or rice bran, we evaluated the effects of a purifying paddy field which is no fertilizer, no pesticides, and dense rice seedling having a concept of constructed wetland. The experimental paddy field was located at downstream in the watershed of ducks using rice culture area in Milyang. The purifying paddy of land design were treated with seeding method, and vegetation type. As land design, direct seeding on plane, and direct seeding on high-ridge field in 2007. Planting rice only, and planting rice with water hyacinth were treated as vegetation type in purifying paddy in 2008. The purifying paddy fields were effective to reduce amount of T-N and T-P contents in effluent to 33.2~45.3%, and 53.1~55.4%, respectively. The direct seeding on high-ridge treatment, having long residence time of effluent water was more effective than plane plot as T-N 0.29 $g^{-1}m^{-2}d^{-1}$, and T-P 0.031 $g^{-1}m^{-2}d^{-1}$. The planting rice with water hyacinth treatment was effective than planting rice only as T-N 0.23 $g^{-1}m^{-2}d^{-1}$, and T-P 0.049 $g^{-1}m^{-2}d^{-1}$. The optimum area of purifying paddy field to treats all effluent were found out 3.2~4.7% of rice culture area using free range ducks, and rice bran at upper stream.

• Korean Journal of Soil Science and Fertilizer
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• v.19 no.3
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• pp.239-244
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• 1986

This study was conducted to investigate the characteristics of humic substances and the fractional distribution of organic nitrogen in Korean paddy soils. The results are obtained as follows: 1. The content of humus in soils used was 665-2680 mg/100g and the average contents of humic acid in normal paddy soils and in sandy paddy soils were 1436 mg/100g, 970 mg/100g respectively. 2. The humic acid diagrams classed by Kumada method belong to B type, P type and Rp type. 3. The content of Mineral - N to Total - N was 1.04-2.86% and the average contents of that in sandy paddy soils and in normal paddy soils were 1.72% and 1.75% respectively. 4. The fractionations of acid hydrolysable organic - N in sandy paddy soils were Amino acid - N (31.52%), Humin - N (20.63%), Amino sugar - N (18.70%), and Unknown - N (25.73%).