• Korean Journal of Organic Agriculture
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• v.26 no.4
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• pp.629-647
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• 2018

This study was carried out to investigate the economic value of organic rice production using gelatin chitin microorganisms in eco-friendly complex, Gongsan, Naju city. The soil condition of experiment paddy field was Jeonbuk series and silt loam with a slightly poor drainage. Except for the high effective silicate, the chemical characteristics of soils used were included in the optimum range of paddy soils in Korea. In growth, plant length, tiller number, ear number, and ear length were observed to be higher in conventional paddy fields than organic paddy fields. However, number of grain per panicle and grain filling ratio (%) were higher in organic paddy fields than conventional paddy fields. Incidences of diseases and insect pests were slightly higher in the organic paddy fields. Water weevil, sheath blight, rice leaf roller and rice blast were more occurred in organic paddy field. On the other hand, false smut was higher occurred in conventional paddy field. There was a significant negative correlation between rice sheath blight and rice leaf roller, and rice yield. In the milled rice quality, the quality of organically cultivated milled rices was lower by the increase of broken rice than that of conventionally cultivated milled rices. The quality and palatability of rice were higher in organic cultivation with decreasing of protein content. Net income of conventionally and organically cultivated rice was 360,000 won/10a and 610,000 won/10a, respectively. Premium net income of the organically cultivated rice was 68%.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.319-319
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• 2017

Methane is the main greenhouse gas released from rice paddy field. Methane from paddy fields accounts for 11 % of the global total methane emission. The global warming potential (GWP) of methane is 25 times more than that of carbon dioxide on a mass basis. It is well known that most effective practice to mitigate methane in paddy is related to the water management during rice growing season and the use of organic matters. This study was conducted to investigate the effects of tillage and cultivation method on methane emission in paddy. Tillage (tillage and no-tillage) and cultivation methods (transplanting and direct seeding) were combined tillage-transplanting (T-T), tillage-wet hill seeding (T-W), tillage-dry seeding (T-D) and no-till dry seeding (NT-D) to evaluate methane mitigation efficiency. Daily methane emission was decreased on seeding treatments (T-W, T-D, NT-D) than transplanting treatment (T-T). Amount of methane emission during rice growing season is highest in T-T ($411.7CH_4\;kg\;ha^{-1}y^{-1}$) and lowest in NT-D treatment (89.7). In T-W and T-D treatments, methane emissions were significantly decreased by 36 and 51 % respectively compared with T-T. Methane emissions were highly correlated with the dry weight of whole rice plant ($R^2=0.62{\sim}0.93$). T-T treatment showed highest $R^2$ (0.93) among the four treatments. Rice grain yields did not significantly differ with the tillage and cultivation methods used. These results suggest that direct seeding practice in rice production could mitigate the methane emissions without loss in grain yield.

• Journal of Biosystems Engineering
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• v.29 no.2
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• pp.109-120
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• 2004

To obtain basic information for precision agriculture, spatial variability of rice growth condition was evaluated in 100m ${\times}$100m paddy field. The rice growth condition of four hundred locations in the field were investigated to analyze the spatial variability of their properties ; SPAD, plant length and tiller number. Geostatistical analysis was carried out to examine within-field spatial variability using semivariograms and kriged maps as well as descriptive statistics. Descriptive statistics showed that the coefficient of variation for SPAD, plant length, and tiller number exceeded 5.70 %, suggesting a relatively high variability. Geostatistical analysis indicated a high spatial dependence for all the properties except for the second tiller number. The range of spatial dependence was about 20 m for SPAD, plant length, and tiller number. Based on the results of spatial dependence, kriged maps were prepared for the properties to analyse their spatial distribution in the field. The results reflected the history of field management. In conclusion, the need for site-specific field management and possibility of precision agriculture were demonstrated even in an almost flat paddy field.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.463-472
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• 2023

The insecticidal activities of 27 different commercial products with environmentally friendly organic material(EFOM) against Scotinophara lurida, a major rice pest, were evaluated in the laboratory using spraying methods on plants and insects. Seven plant-derived organic farming materials (EFOM-8, -10, -12, -13, -19, -20, and -26) with high insecticidal effects when sprayed directly on the insect's body rather than on the plant were selected. In the indoor rice pot test, all 7 EFOMs showed an insecticidal rate of over 73.3% under flooding conditions. Notably, EFOM-13 and EFOM-20 demonstrated much higher insecticidal rates, ranging from 1.5 to 1.8 times, in flooding conditions compared to drained conditions. In the semi-paddy field test, EFOM-10 (80% garlic extract), EFOM-13 (62% neem extract), and EFOM-26 (70% sophora extract+28% ethyl alcohol+2% pyrethrum extract) exhibited a higher control value of 88.9% in the irrigated paddy on the 7th day, surpassing the control values in the drained paddy by 1.4 to 1.9 times. The control value in the irrigated rice paddy field sprayed with EFOM-10 reached 86.2% on the 7th day, which was 1.4 times higher than 61.9% in the drained paddy. Taken together, the findings suggest that direct contact of the insect's body with sufficient amounts of spray solution and the maintenance of paddy irrigation can enhance the controlling effect of EFOMs. These findings will be valuable in developing an optimal S. lurida control strategy for application in rice paddy fields in the near future.

• Journal of Biosystems Engineering
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• v.9 no.1
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• pp.11-21
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• 1984

This study was intended to analyze the dynamic force system which induced the shattering of paddy grains. A model to predict the shattering of paddy grains was developed, and physical quantities, such as mass distribution and rigidity of rice plant, needed for evaluating the minimum shattering forces were also measured. Under the assumption that rice plant right before harvesting is a vibratory system, the mathematical model of the vibratory system was developed and solved with the varied conditions of forcing functions. The results of the study were summarized as follows: 1. The shattering of grain occurred at the abscission layer of grain by the bending moments resulted from the impact force due to the collision of panicles of rice plant. 2. The vibratory model developed for milyang 23 rice variety was analyzed to give the natural frequencies of 7-9 Hz, which were closely related with the excitation frequencies of 4-10 Hz caused by various machine parts besides engine. Thus, avoiding the resonance should be taken into consideration in the design of the harvesting machinery. 3. It was analyzed to predict the lowest frequency that could develop the shattering when the excitation force was applied to the lower end of stem. The lowest frequency for the Milyang 23 rice variety ranged from 8.33 Hz to 11.66 Hz as the amplitude varied from 1 cm to 2.5 cm. 4. The degree of shattering depended upon the magnitude of the impact force and its application point. For Milyang 23 rice variety, the minimum impact force developing the shattering was $5g_f$ when it was applied at 1 cm above the lower end of stern and $1g_f$ when applied at 5 cm above the lower end of stem. 5. The minimum colliding velocity of the panicle, when it was on the ground that would just develop the shattering, was given as follows, $$V=\sqrt{\frac{K_t}{m_g}{\cdot}{{\phi}^2}}$$ where V : The colliding velocity of the panicle against ground to cause the shatteering of rice grain. (cm/sec) $K_t$ : The minimum spring constant for bending at the abscission layer of grain. (dyne-cm/rad) ${\phi}$ : The minimum shattering angle of grain (rad) $m_g$ : The maximum mass of grain. (g).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.1
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• pp.16-21
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• 2005

This study was conducted to establish the elaborate nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy. The nitrogen uptake by rice plants was insignificant until 25 days after seeding, and increased gradually thereafter. During this early growth stage, rice plants absorbed only the $4\%$ of basal applied N, while the $45\%$ of N fertilizer remained in the paddy soil. The absorption of basal N by rice plants was almost completed at 46 days after application. Nitrogen top-dressed at 5-leaf stage was well matched to crop nutrient demand, so it could be absorbed so actively in 8days after application. As a result, we could cut down the amount of N fertilizer to $36\%$ of the basal N level without significant difference in yield. Plant recoveries of fertilizer $^{15}N$ applied with different application timings were $7.8\%$ for basal, $9.4\%$ for 5-leaf stage, $17.1\%$ for tillering stage, and $23.4\%$ for panicle initiation stage, respectively. When urea was applied with nitrogen fertilization practice based on basal incorporation (BN), plant recovery of $^{15}N$ at harvest was $31.0\%$, which was originated from $13.7\%$ for grain, and $21.3\%$ of the fertilizer $^{15}N$ remained in the soil, and the rest could be uncounted. Plant recovery of fertilizer $^{15}N$ applied with nitrogen fertilization practice based on topdressing at 5-leaf stage (TN), where N rate was reduced by $18\%$ compared with BN, was $35.1\%$ (grain $15.6\%$), and $19.9\%$ of the fertilizer $^{15}N$ remained in the soil, and the rest could be uncounted. TN showed a higher $^{15}N$ recovery than BN because it was to apply N fertilizer at a time to well meet the demand of rice plant direct-seeded on flooded paddy. We concluded that TN would be the nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy.

• The Korean Journal of Mycology
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• v.12 no.2
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• pp.65-73
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• 1984

Strain IV caused highest reduction of germination and caused abnormal elongation of all part of the plant which finally died. Milyang 23 and Nampungbyeo formed mesocotyl. Samnambyeo and Jinjubyeo did not formed mesocotyl on the soil surface in nursery boxes when they were planted on soil infested with each strain of F. moniliforme. Infected seedlings with mesocotyl recovered after transplanting in the the field. The most frequency of Strain IV was isolated from infected rices and this strain was isolated from all part of rice. When rice seedling infected with Strain IV were transplanted in paddy field, most of rice showed Bakanae symptom. Ear emergence of rice was more delayed when seedlings infected with Strain IV were transplanted than that of healthy plant. Number of panicle per hill and grain yield from rice when infected rice seedling by Strain IV were transplanted were more decreased than that of the healthy plant in paddy field.

• Korean Journal of Weed Science
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• v.10 no.2
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• pp.103-108
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• 1990

Germination test, nutrient culture test and pot experiment were conducted to determine selectivity of naproanilide between rice plants and paddy weeds. Naproanilide more severely inhibited growth of Scirpus juncoides, Sagittaria pygmaea and Cyerus serotinus than that of rice plant and Echinochloa crus-galli at germination stage. Root growth was severely inhibited than that of shoot growth by naproanilide treatment. Naproanilide severely inhibited rice plant and Echinochloa crus-galli at 30 uM, Sagittaria pygmaea at 1 uM and Cyperus serotinus at 10 uM in nutrient culture test, Rice plant and Echinochloa crus-galli did not show the difference of tillers and dry weight, but Scirpus juncoides, Morzochoria vaginalis and Aneilema keisak were severely inhibited at 15g/a and Sagittaria pygmaea and Cyperus serotinus at 30g/a in pot trial.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.1
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• pp.135-143
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• 2018

The effect of elevated temperature on temperate paddy rice will be significant for dependable food supply in East Asia. Using temperature gradient field chamber (TGFC), which was designed to make the horizontal air temperature gradient by $0^{\circ}C$ to $3^{\circ}C$ higher than outside, we examined the measurement to understand the effects of extremely high temperature on paddy rice. In particular, the data of the year 2016, the worst heat wave in over 22 years, was analyzed in this study. The rice height in the relatively warmed condition was rapidly increased during early growth stage. However, the average grain weight and number of spikelet per panicle in the warmed chamber condition were gradually declined with increasing air temperature averaged for 40 days after first heading in each chamber. In particular, the grain yield was more dramatically decreased by the raising temperature because the percent ripened grain was quickly dropped as getting over the threshold temperature for pollination. Therefore, the surplus photosynthetic product by such lower grain filling rate may disturbed the decreases of the NDVI (Normalized Difference Vegetation Index) and SPAD chlorophyll values after first (normal) heading. In addition, the late-emerging head grain were appeared. However, this yield was too small to recover the normal yields decreased by extremely high temperature condition. Our result represented that the warmed condition in 2016 would be the critical limit for the stable yield of temperate paddy rice.

• Korean Journal of Plant Resources
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• v.16 no.3
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• pp.181-186
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• 2003

In order to evaluate the effect of salinity content in soil on chemical composition and productivity of rice which is suitable for the reclaimed saline paddy field, yield components and yield were investigated in 2,000 at reclaimed paddy field of Kwangyang bay in Korea. Heading date was early with Aug. 15 in soft salinification of 0.1 percent and late with from Aug. 20 to Aug. 25 in heavy salinification of 0.4 and 0.8 percent. Brown rice yield was highest in soft saliniflcation of 0.1 percent with 599kg/10a and was decreased with from 568kg/10a to 446kg/10a in heavy salinification of 0.4 and 0.8 percent. The correlation coefficient between brown rice yield and content of soil chemical composition, on organic matter, phosphate, nitrogen, potassium, calcium, and magnesium showed highly positive correlation and was shown negative correlation with pH meter. Judging from the results reported above, optimum salinification of saline paddy field seemed to be 0.1 percent.