• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.3
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• pp.352-356
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• 1997

In order to trace the survival route of weedy rice in Korean farmer's field, occurrence rate and position of weedy rice, number of weedy rice plants per $m^2$, in transplanted and direct seeded field were investigated. The highest occurrence rate of weedy rice in transplanted field was 5.5％. Number of weedy rice plants in direct seeded field was higher than that in transplanted field. In transplanted field, most of the weedy rice were grown within hills of cultivated rice and only a few was grown between hills of the cultivated rice, however in direct seeded field the number of weedy rice occurred between hills or rows of cultivated rice was higher than that occurred within hills or rows. Weedy rice occurrence rate in the field of .non-recommended rice variety was higher than that in the field of recommended variety. The main survival route of weedy rice in transplanted field was supposed to be mixture of weedy rice seeds with cultivated rice, and that in direct seeded field to be natural survival.

• Korean Journal of Organic Agriculture
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• v.13 no.3
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• pp.291-300
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• 2005

Diseases were surveyed in 5 Rice paddy field areas of Organic paddy field and conventional paddy field. The 3 major diseases, rice leaf blast, bacterial leaf blight and sheath blight in rice were surveyed at duck raising, rice bran and conventional rice paddy field. They were serious in duck raising paddy field, rice bran paddy field more than conventional paddy field. The Ilpum variety were infected seriously more than Chucheong. At the effectivity test of the environment-friendly substance for the rice-seed sterilization, 1000-times diluted brown-rice vinegar showed controlling effect against Bakanae disease, and germination rate also was good. There was no Weeds Control efficacy by cultivating of hairy vetch in rice paddy field. However, extract of hairy vetch Leaf and root repressed the germinating of lettuce seed.

• Korean Journal of Organic Agriculture
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• v.9 no.3
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• pp.45-71
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• 2001

The duck-rice forming system is increasingly spread up throughout Korea since 1992. It is discussed the rice field, rice quality, weed and pest management in the duck-rice weeding system compared to conventional farming system. Moreover the optimizing duck population, system management and fertilizer application rate were reported. Energy input and output by duck-rice farming system were carefully compared with those of low input sustainable paddy field and conventional farming paddy field. To find out the environmentally sound function of duck-rice system, the total nitrogen in paddy soil and paddy water, and nitrogen cycle in paddy rice cultivation system were analysed. finally the input and output were calculated, and ecological characteristic were determined in terms of nitrogen balance, labor input, animal input, renewable energy input, turnover of soil organic matter, energy loss, non-renewable indirect and direct energy input. It was concluded duck-rice weeding system could be recommended in terms of net only environmentally sound, but also farmer's income. But there are still some research needs for successful adaption of duck-rice farming to investigate to determine the optimal population of duck in rice paddy field unit, release time of duckling, duck management after release, and strategy for duck marketing and duck processing.

• Animal cells and systems
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• v.8 no.4
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• pp.281-288
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• 2004

The change in relationships between methane production and sulfate reduction was investigated in reclaimed rice field soils at different time points after reclamation of tidal flat in Korea. Sulfate concentrations of soils in the ca. 60-year-old and 26-year-old reclaimed rice fields were much lower than that in a natural tidal flat. During 60 d of anaerobic incubation, total methane production and sulfate consumption of the soil slurries were 7.0 ${\mu}$mol $CH_4$/g and 8.2 ${\mu}$mol $SO_4^{2-}$/g in the 60-year-old rice field, 5.6 ${\mu}$mol $CH_4$/g and 12.7 mmol $SO_4^{2-}$/g in the 26-year-old rice field, and ca. 0 mmol $CH_4$/g and 22.4 ${\mu}$mol $SO_4^{2-}$/g in a natural tidal flat. Relative percent electron flow through sulfate reduction in the 60-year-old rice field was much lower (50.8%) compared with the 26-year-old rice field (69.3%) and the tidal flat (99.9%). The addition of an inhibitor of methanogenesis (2-bromoethanesulfonate) had no effect on sulfate reduction in the soil slurries of the reclaimed rice fields. However, instant stimulation of methane production was achieved with addition of an inhibitor of sulfate reduction (molybdate) in the soil slurries from the 26-year-old reclaimed rice field. The specific inhibitor experiments suggest that the relationship of methanogenesis and sulfate reduction might become mutually exclusive or syntrophic depending on sulfate content in the soil after reclamation. Sulfate, thus sulfate reduction activity of sulfate-reducing bacteria, would be an important environmental factor that inhibits methane production and determines the major pathway of electron and carbon flow in anaerobic carbon mineralization of reclaimed rice field soils.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.468-473
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• 1999

This study was carried out to assess the use of RADARSAT data which is C-band with HH polarization for the rice growth monitoring in Korea. Nine time-series data were taken by shallow incidence angle (standard beam mode 5 or 6) during rice growing season. And then, backscatter coefficient ($\sigma$$^{\circ}$) were extracted by calibration process for comparing with rice growth parameters such as plant height leaf area index(LAI), and fresh and dry biomass. Field experimental data concerned with rice growth were collected 8 times for the ground truth at the study area, Tangjin, Chungnam, Korea. At the maximum vegetative stage of rice, backscatter coefficients were the highest at the flooded rice field ranging from -4.4dB~-3.1dB. The temporal variation of backscatter coefficient($\sigma$$^{\circ}$) in rice field was significant in this study Backscatter coefficient ($\sigma$$^{\circ}$) of rice field was a little bit lower again after heading stage. This results show RADARSTA data is promising for rice monitoring.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.4
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• pp.232-236
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• 2000

To obtain a basic information on the development of effective control strategies for weedy rice in direct seeding rice cultivation, occurrence patterns of weedy rice as influenced by different cultural practices such as cultivation method, water management, seeding time, and tillage were investigated in field or pot experiments. High occurrence of weedy rice was observed in a continuous direct seeding paddy field as compared to machine transplanted one. Based on the percent of weedy rice panicle over three years trial, high ridged dry seeding was highest with 36.9%, followed by wet seeding with 30.9%, water seeding with 14.6% and machine transplanting rice with 0.8%, indicating 97.8% reduction in weedy rice occurrence by machine transplanting rice as compared with high ridged dry seeding. Germination of weedy rice was promoted to 83-94 % when rice panicle was flooded from September 30 to October 10 for 6 days and 74-88% for 9 days on October 20. Weedy rice occurrence was also substantially reduced by delayed seeding on June 10 and intensive tillage. The results suggest that machine transplanting rice be more effective cultural practice than flooding treatment, delayed seeding and intensive tillage when weedy rice problem occurs in direct seeded paddy field.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.4
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• pp.370-374
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• 1990

A field experiment was conducted to investigate the influence of water weevil damage on growth and grain guality in rice. Plant height was shortened, number of tillers per hill decreased and maximum tillering stage delayed in damaged field by rice water weevil. Heading date was delayed by 1-2days, culm lenght shortened, panicle lengthened, number of panicles decreaced, number of panicles per spikelet increased, ripened grain ratio decreased in damaged field by rice water weevil. Yield per 10a was decreased 4-22% in damaged field compared with that in undamaged field by rice water weevil, yield loss in late transplanting (June 23) was larger than that in early transplanting (May 20). Imperfect kerml rice, especially green kernel rice, was increased in damaged field by rice water weevil.

• Korean Journal of Organic Agriculture
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• v.13 no.3
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• pp.301-314
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• 2005

Insect pests were surveyed in 5 Rice paddy field areas of Organic paddy field and conventional paddy field. At the each rice-growth period, the occurrence rate of 'Small brawn plant hopper was high at the case of duck raising and rice bran farming on middle stage of rice paddy field in Gang-Hwa region. The occurrence rate of Rice water weevil was high at the conventional paddy field on the early stage of rice paddy field in Yeo-Ju region. In the Hong-Seong region, the occurrence rate of 'Rice water weevil' and 'Green rice leafhopper' was high at the 'duck raising compare to the conventional farming on the early stage of rice paddy field. According to each period, the occurrence rate of insect was high at late stage of rice paddy field, and there was no difference between each region. It showed high-occurrence tendency at duck pasture farming rice paddy field. The major natural enemies were spiders and parasites. Theridiidae and Linyphiidae were highly occurred on the conventional farming rice paddy field in Hong-Seong. Web builders containing Theridiidae, Linyphiidae and Tetragnathidae was occurred more than wandering spiders containing Lycosidae, Clubionidae and Pisauridae at various regions, and then occurrence of spiders was different at the various regions but was not different at each farming system.

• Korean Journal of Remote Sensing
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• v.16 no.2
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• pp.109-116
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• 2000

This study was carried out to assess the use of RADARSAT data which is C-band with HH polarization for the rice growth monitoring in Korea. Nine time-series data were taken by shallow incidence angle (standard beam mode 5 or 6) during rice growing season. And then, backscattering coefficients ($\sigma$$^{\circ}$) were extracted by calibration process for comparing with rice growth parameters such as plant height, leaf area index(LAI), and fresh and dry biomass. Field experimental data concerned with rice growth were collected 8 times for the ground truth at the study area, Tangjin, Chungnam, Korea. At the beginning of rice growth, backscattering coefficients were ranged from -l6~-l3dB when rice fields were not covered with rice canopy and flooded. At the maximum vegetative stage of rice, backscattering coefficients of the rice field were the highest ranging from -4.4dB~-3.1dB. The temporal variation of backscattering coefficient($\sigma$$^{\circ}$) in rice field was significant in this study. Backscattering coefficient ($\sigma$$^{\circ}$) of rice field was a little bit lower again after heading stage than before. This results show RADARSAT data is promising for rice monitoring.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.59-64
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• 2006

Application of herbicide for rice cropping is inevitable but notorious for its side effect of environmental pollution. Precision fanning will be one of important tools for the least input and sustainable fanning and could be achieved by implementation of the variable rating technology. If a device to detect weeds in rice field is available, herbicide could be applied only to the places where it is needed by the manner of the variable rating technology. The study was carried out to develop an algorithm of image processing to detect weeds in rice field using a machine vision system of multi-spectral digital images. A series of multi-spectral rice field picture of 560, 680 and 800 nm of center wavelengths were acquired from the 27th day to the 39th day after transplanting in the ineffective tillering stage of a rice growing period. A discrimination model to distinguish pixels of weeds from those of rice plant and weed image was developed. The model was proved as having accuracies of 83.6% and 58.9% for identifying the rice plant and the weed, respectively. The model was used in the algorithm to differentiate weed images from mingled images of rice plant and weed in a frame of rice field picture. The developed algorithm was tested with the acquired rice field pictures and resulted that 82.7%, 11.9% and 5.4% of weeds in the pictures were noted as the correctly detected, the undetected and the misclassified as rice, respectively, and 81.9% and 18.0% of rice plants in the pictures were marked as the correctly detected and the misclassified as weed, respectively.