• Korean Journal of Weed Science
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• v.30 no.3
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• pp.282-290
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• 2010

The objective of this research was to discover the best method for weed management in environment-friendly rice paddy fields through the study on the effect of weed control and injury levels of rice plants as affected by size, input time, and input amount of golden apple snail (GAS). The efficacy of weed control as affected by GAS when applied at 5, 10, and 15 days after transplanting (DAT) was 98, 89, and 58%, respectively. The efficacy of weed control had declined as late the input time of GAS. On the other hand, the efficacy of weed control as affected by rice bran followed by GAS treatment was higher than by GAS treatment alone. Weed species such as Persicaria hydropiper, Echinochloa crus-galli, Scirpus juncoides, and Monochoria vaginalis were not completely controlled by GAS when applied late. Input amount and time of adult GAS (70 days after hatching) for effective weed control were 3 kg $10a^{-1}$ at 5 DAT, 6-7 kg $10a^{-1}$ at 10 DAT, and 7 kg $10a^{-1}$ at 15 DAT. Input time and amount of young GAS (35 days after hatching) for effective weed control were 0 day after harrow (DAH) and 1 kg $10a^{-1}$, respectively. The young GAS when applied 0 DAH at 1 kg $10a^{-1}$ provided 100% control of P. hydropiper, E. crus-galli, S. juncoides, M. vaginalis, Ludwigia prostrata, Eleocharis kuroguwai, Sagittaria trifolia and Cyperus difformis. The rice foliar injury caused by adult (3 kg $10a^{-1}$) and young (1 kg $10a^{-1}$) GAS were 5-7% and 1% respectively. There was no significant difference in rice injury by size and input amount of GAS on plant height and number of tiller. These data indicate that the young GAS when applied 1 kg $10a^{-1}$ at 0 day after harrow was the best method for weed management in environment-friendly rice paddy fields.

• Korean Journal of Weed Science
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• v.30 no.3
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• pp.272-281
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• 2010

The objective of this research was to find out the weed management techniques in environment-friendly rice paddy fields through the study on herbicidal effects and problems of various organic materials. This experiment was conducted under different conditions of weed species and weed densities in environment-friendly rice paddy fields. There was no difference in weedy efficacy on golden apple snail (GAS), paper mulching (PM), and machine weeding (MW) between low and high weed densities. However, the effect of weed control in rice bran (RB) and effective microorganism (EM) + molasses was higher in high weed density than in low weed density. In general, the effect of weed control as affected by various organic materials was in the order of GAS (97-100%) > PM (93-98%) > RB (15-80%) > EM (7-31%). GAS provided excellent control of all weed species tested except for Persicaria hydropiper. PM gave acceptable control of the weed species except for Echinochloa crus-galli, Ludwigia prostrata, and Eleocharis kuroguwai. However, MW gave fair control (70% biomass reduction) of all weed species tested. BR followed by MW or EM followed by MW treatments had similar effect on weed control compared to each treatment alone. However, BR followed by GAS or EM followed by GAS provided 100% control of weed species tested. The level of rice foliar injury caused by various organic materials was in the order of GAS and MW (10-20%) > RB (10-15%) > PM and EM (5-7%). Typical symptoms of organic materials are wilting, inhibition of growth, missing hill, and reduction of tiller. Cost for weed control of GAS, RB, EM, and PM were 2.1, 3.1, 2.3, and 13.2 times higher than that of the herbicide. These data indicate that GAS was the best method for weed management in environmentfriendly rice paddy fields. Further study is required to elucidate the mechanisms underlying the rice injury as affected by GAS.

• Journal of The Korean Society of Grassland and Forage Science
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• v.38 no.1
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• pp.44-52
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• 2018

This experiment was conducted at Suwon, Korea from 2013 to 2015. The objective of this study was to establish the optimum seeding rate, and to clarify the nitrogen fertilizer level for rye seed production in central and north area of Korea. We used Korean rye cultivar 'Gogu' for this test. We employed a split-plot design with three replications. The main plots were designed by three seeding levels (3, 5 and $7kg\;10a^{-1}$), but other sub-plots were randomly seeded. The plots were treated with three different nitrogen fertilizer levels (3, 6 and $9kg\;10a^{-1}$). The percentage of productive tiller, number of grain per spike, fertility rate, 1 liter weight, and 1000-grain weight decreased as seeding rate increased from $3kg\;10a^{-1}$ to $7kg\;10a^{-1}$, whereas the number of spike per $m^2$ increased. Therefore the grain yields of rye had less of an effect by increasing seeding rate. There was an increase in number of spike per $m^2$, number of grain per spike, and fertility rate as nitrogen fertilizer level increased from $3kg\;10a^{-1}$ to $9kg\;10a^{-1}$, but grain yields significantly not affected by the interaction of seeding rate ${\times}$ nitrogen fertilizer levels. However, the best seeding rate and nitrogen fertilizer level for rye seed production were 5 kg and $5{\sim}6kg\;10a^{-1}$, respectively, considering seed and fertilizer reduction and the prevention of pollution by excess fertilization.

• Korean Journal of Agricultural Science
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• v.12 no.1
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• pp.101-107
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• 1985

Since most farmers breeding livestocks in Korea is depended on imported feeds, the rate of self-supplying feeds is very important for a stable development of farmers. Therefore, it is considered necessary to increase the rate of self-supplying feeds. In this study, performance tests were carried out with barley and forage to find the design's parameters of hammer for a small size hammer mill which can be driven by 3.7-7.5 kW power tiller being used by most farmers. The revolution speed of hammer mill was 3000 rpm, widths of hammer were 20mm, 30mm, 40mm, and the levels of thickness of hammer were 2mm, 4mm and 6mm. Experimental materials used were barley and forage and screen openings for barley was 4.76mm, and 3.18mm for forage. The study results can be summarized as follows; 1. Results of grinding tests showed that particle sizes were 478-774 microns for barley and 350-434 microns for forage. They were decreased according to the increasing thickness and width of hammer. 2. Fineness modulus of grinded materials were 3.07-3.62 for barley and 2.69-2.93 for forage. They were inversely proportional to thickness and width of hammer. 3. The required power for grinding was 3.8-5.0 kW for barley and 0.9-1.4 kW for forage. The thickness of hammer was more important for less power requirement than width of hammer. 4. Grinding performance of a small size hammer mill was 99-170kg/kWh for barley and 11-21 kg/kWh for forage. The thickness of hammer was an important factor for grinding performance, and inversely proportional to grinding performance. For about 3.2 of fineness modulus, 4 mm thickness was the best, and an optimum width of hammer was 30mm for a small size hammer mill.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.2
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• pp.113-118
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• 2016

This experiment was conducted to identify the variations in inorganic nutrients and plant growth in millet (Panicum miliaceum L.) due to soil salinity. The soil series was Munpo and soil texture was silt loam. The experimental soil was amended so that the soil had salinities of $0.8dS\;m^{-1}$, $1.6dS\;m^{-1}$, $3.2dS\;m^{-1}$ and $4.8dS\;m^{-1}$. Millet was transplanted 15 days after sowing. As soil salinity increased, the degree of reduced growth was in the order of seed production > root dry matter > plant dry matter > culm length > tiller number > stem thickness > Panicle length. Seed production was decreased to 18.9% in soil salinity of $1.6dS\;m^{-1}$, 36.9% in of $3.2dS\;m^{-1}$, and 50.7% in EC of $4.8dS\;m^{-1}$. Root dry matter decreased to 35.8% in EC of $3.2dS\;m^{-1}$, and to 40.5% in EC of $4.8dS\;m^{-1}$. As soil salinity increased, Total nitrogen content increased in all aboveground parts, roots and seeds. However, There was no difference in CaO, $P_2O_5$, $K_2O$ and, MgO in soils of different salinity. On the other hand, $Na_2O$ content was higher in the order roots> shoots> seed, and in the case of roots, $Na_2O$ content increased to 1.02% in soil salinity of $4.8dS\;m^{-1}$. However, up to soil salinity of $1.6dS\;m^{-1}$, the $Na_2O$ content of the seed was similar to that in plant grown in the Control conditions($0.8dS\;m^{-1}$). In conclusion, taking into consideration economic factors, millet could be cultivated in soil with salinities of up to approximately $1.6dS\;m^{-1}$, and seed produced from reclaimedland would be suitable for human consumption.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.64 no.4
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• pp.384-394
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• 2019

We have investigated the effects of ambient temperature on the growth of wheat in Korea. The differences in the growth phase of wheat were compared according to the temperature treatment. The productive tiller number and dry weight were decreased in a plot under a higher temperature treatment. We found that the growth of Jinpum was different from that of the alternative wheat cultivars, which were bred in Korea, at 50 days after treatment. While the Jinpum wheat grown at 17℃ showed vegetative stage growth, that grown in the 23℃ growth chamber entered the heading and flowering stage. The differences in the expression of 16 genes known to be involved in high-temperature responses were checked by using Jinpum wheat 50 days after two temperature treatments (17℃ and 23℃), which showed apparent differences in expression between the higher and lower temperatures during the growth phase. In the 23℃ treatment samples, the genes with increased expression were HSP70, HSP101, VRN2, ERF1, TAA1, YUCCA2, GolS, MYB73, and Histone H2A, while the genes with decreased expression were VRN-A1, DREB2A, HsfA3, PIF4, PhyB, HSP17.6CII, rbcL, and MYB73. YUCCA2, HSP101, ERF1, and VRN-A1 showed a significant difference in gene expression between lower- and higher-temperature conditions. Overall, combining the means of the expression of various genes involved in thermosensing, vernalization, and abiotic stresses, it is possible to conclude that different sets of genes are involved in vernalization and summer depression of wheat under long term, high ambient temperature conditions.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.s02
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• pp.45-65
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• 1989

The Korean peninsular having the complexity of the photography and variability of climate is located within passing area of a lots of typhoon occurring from the southern islands of Philippines. So, there are various patterns of wind and flooding damages in paddy field occuring by the strong wind and the heavy rain concentrated during the summer season of rice growing period in Korea. The wind damages to rice plants in Korea were mainly caused by saline wind, dry wind and strong wind when typhoon occurred. The saline wind damage having symptom of white head or dried leaves occurred by 1.1 to 17.2 mg of salt per dry weight stuck on the plant which was located at 2. 5km away from seashore of southern coastal area during the period(from 27th to 29th, August, 1986) of typhoon &Vera& accompanying 62-96％ of relative humidity, more than 6 m per second of wind velocity and 22.5 to 26.4$^{\circ}C$ of air temperature without rain. Most of the typhoons accompanying 4.0 to 8. 5m per second of wind and low humidity (lesp an 60％) with high temperature in the east coastal area and southen area of Korea. were changed to dry and hot wind by the foehn phenomenon. The dry wind damages with the symptom of the white head or the discolored brownish grain occurred at the rice heading stage. The strong wind caused the severe damages such as the broken leaves, cut-leaves and dried leaves before heading stage, lodging and shattering of grain at ripening stage mechanically during typhoon. To reduce the wind damages to rice plant, cultivation of resistant varieties to wind damages such as Sangpoongbyeo and Cheongcheongbyeo and the escape of heading stage during period of typhoon by accelerating of heading within 15th, August are effective. Though the flood disasters to rice plant such as earring away of field, burying of field, submerging and lodging damage are getting low by the construction of dam for multiple purpose and river bank, they are occasionally occurred by the regional heavy rain and water filled out in bank around the river. Paddy field were submerged for 2 to 4 days when typhoon and heavy rain occurred about the end of August. At this time, the rice plants that was in younger growing stage in the late transplanting field of southern area of Korea had the severe damages. Although panicles of rice plant which was in the meiotic growing stage and heading stage were died when flooded, they had 66％ of yield compensating ability by the upper tilling panicle produced from tiller with dead panicle in ordinary transplanting paddy field. It is effective for reduction of flooding damages to cultivate the resistant variety to flooding having the resistance to bacterial leaf blight, lodging and small brown planthopper simultaneously. Especially, Tongil type rice varieties are relatively resistant to flooding, compared to Japonica rice varieties. Tongil type rice varieties had high survivals, low elongation ability of leaf sheath and blade, high recovering ability by the high root activity and photosynthesis and high yield compensating ability by the upper tillering panicle when flooded. To minimize the flooding and wind damage to rice plants in future, following research have to be carried out; 1. Data analysis by telemetering and computerization of climate, actual conditions and growing diagnosis of crops damaged by disasters. 2. Development of tolerant varieties to poor natural conditions related to flooding and wind damages. 3. Improvement of the reasonable cropping system by introduction of other crops compensating the loss of the damaged rice. 4. Increament of utilization of rice plant which was damaged.