• Korean Journal of Soil Science and Fertilizer
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• v.44 no.2
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• pp.176-180
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• 2011

Rice production depended on the weed control. The purpose of this study was conducted to evaluate the influence of tillage with chemical amendments + 5 cm flooded, no-tillage without Chinese milk vetch + 5 cm flooded (NTNT 5 cm), no-tillage amended with Chinese milk vetch + 5 cm flooded (NTCM 5 cm), and no-tillage amended with Chinese milk vetch + 10 cm flooded (NTCM 10 cm) on weed occurrence and yield of rice in paddy. Triplicate experimental plots were laid out in a randomized complete block design and compared by employing least significant difference. The dry weights of weeds in NTCM 5 cm and NTCM 10 cm were 11% and 4% level of NTNT 5 cm (p<0.05) and were 3.2 times and 1.2 times more than in conventional tillage system. In addition, the Aneilema keisak and Ludwigia prostrata were significantly increased in NTNT 5 cm (p<0.05). The yield of rice grain in NTCM 10 cm was 2.6 times more than in NTNT 5 cm and was 89% level of conventional tillage system. Our findings suggest that NTCM 10 cm should be enhance of weed control as well as improving of yield of rice in paddy.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.1
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• pp.19-24
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• 2004

Germination and emergence habits of Chinese milk vetch (CMV) were examined to obtain the basic information for the effect of environmental conditions and cultural practices on the seedling density. Seed germination tests with different water potentials, temperatures, and soil and water depths showed the environmental effects on the characters related to seed germination in CMV. Imbibition under different temperatures reflects that initial velocity was rapid at higher temperature, however, the times to full imbibition were not different between 15 and $25^{\circ}$. The optimal germination temperature for CMV germination was ranged from 15 to 20 and the germination was highly affected by water potential of media at relatively high temperature above $20^{\circ}$. When the seeds were sown in flooded condition the germination was not proportionally affected by water depth. In addition, there was no correlation between water depth and oxygen concentration. The germination of seeds flooded by 2cm water depth were poorly germinated compared to other depths. Results indicated that the germination of submerged seeds was more highly influenced by flooding depth than the temperature, it was also affected more strongly at 10 than $20^{\circ}$. Emergence of CMV depending on the thickness of covered soil was poor when the soil layer was greater than 5cm. In the experiment with seeds collected between 22 days after flowering (OAF) and 52 DAF, the highest germination ability of CMV seeds was observed at 39 DAF and germinability was decreased subsequently as seeds became mature. The lower germinability may be due to the enhanced seed dormancy.

• Korean Journal of Environmental Agriculture
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• v.9 no.1
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• pp.9-13
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• 1990

The dissipation of insecticide fenitrothion(O,O-dimethyl O-4-nitro-m-tolyl phosphorothioate), fungicide IBP(S-benzyl O, O-diisopropyl phosphorothioate), and herbicide butachlor(N-butozymethyl-2-chloro-2', 6'-diethylacetanilide) in flooded soil planted with rice plants was investigated in outdoor pot conditions. The half lives of IBP, butachlor and fenitrothion in the flooding water treated with IBP at 98g, butachlor at 352.8g, and fenitrothion at 100g ai/10a, were 3.6, 1.7 and within 1 day, respectively. The concentration of fenitrothion at 5 days after application was found to be less than 0.0lppm. In the case of IBP and butachlor after 20 days, the concentration was 0.025 and 0.004ppm, respectively. The concentration of fenitrothion, IBP, butachlor in a soil depth of 0-3cm was 0.07, 1.45 and 3.37ppm on the 3rd day after application, and below 0.05, 0.18, 0.39ppm after 7 days, respectively. However, 27 days after application concentration of IBP and butachlor at 0-5cm soil depth resulted in 0.04 and 0.05ppm, respectively. The disappearance of pesticides was remarkably rapid, compared to those in the some soil under the laboratory conditions. Differences in the concentration of IBP in different soil profiles were few, but amounts of butachlor were remarkably higher at 0-2cm soil depth than below 2cm soil depth.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.6
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• pp.401-406
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• 2001

This study was conducted to find out the effect of slow-release nitrogen fertilizer, such as latex coated urea(LCU) and Meister10(MS10) on direct seeded rice in flooded soil(FS). Junghwabyeo, and early maturity rice cultivar grown on the plots which were treated with None-nitrogen, urea, LCU and MS10 plot. Growth characteristic, yield and yield components were investigated. Nitrogen uptake-efficiency and physico-chemical properties of soil before-after experiment were analyzed. Plant height and number of tillers $m^{-2}$ in LCU and MS10 plot at early grow stages were higher than those of Urea plot. MS10 and LCU plot showed similar tendency on the plant height but MS10 plot was higher than LCU plot on the number of tillers $m^{-2}$. The number of seedling $m^{-2}$ were no significant differences among None-N, urea, and MS10 plot. Heading date and leaf color were no significant differences among None-N, urea, and MS10 plot. Culm length in LCU and Ms10 plot were longer compared with urea plot, but panicle length were similar among with Urea, LCU and MS10 plot. Number of panicles $m^{-2}$ was highest in MS10 plot and it was similar between LCU and Urea plot. Yield were greater in order of Ms10 > LCU > Urea plot. Nitrogen uptake and nitrogen efficiency were greater in order of MS10 > LCU > urea plot. After the experiment, total content of nitrogen in soil was not changed at all treatments, but pH, P and K of soil were lower than that of before experiment at all treatments.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.spc1
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• pp.47-51
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• 2006

This study was conducted to establish the optimum seeding rate in different soil salinity level for yield stability of broadcasting on flooded paddy surface to the reclaimed saline land of south-western part at Gyehwado substation of the Honam Agricultural Research institute in $2003{\sim}2004$. Soeganbyeo was tested in the Munpo series (fine sand loam) the results obtained is as follows: As seeding rate was higher, the number of seeding stand was increased and the number of seeding stands in the low salinity field is sharply increased than those of the medium salinity field. The length of culm in medium salinity field tends to be shorter than that of the low salinity field and as seeding rate was increased, the lodging is severe. The milled rice yield was increased as up to 9 kg/10a in low and medium salinity soil. Complete rice was no significantly increased over 5 kg/10a seeding rate in low salinity field and over 7 kg/10a seeding rate in medium salinity field. Considering the yield of milled and complete rice, seeding stand and lodging, The proper seeding rate is $5{\sim}7kg/10a$ in low salinity and $7{\sim}9kg/10a$ in medium salinity for broadcasting on flooded paddy surface at the reclaimed saline land of southwestern part.

• Economic and Environmental Geology
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• v.35 no.6
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• pp.553-565
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• 2002

Seasonal variations in vertical distributions of metals were investigated in the contaminated paddy soils around Siheung Cu-Pb-Zn and Deokeum Au-Ag mines. Geochemical behavior of metals was also evaluated with respect to redox changes during the cultivation of rice. Two microcosms simulating the rice-growing paddy field were set up in the laboratory. The raw paddy soils from two sites showed differences in mineralogy, metal concentrations and gecochemical parameters, and it is suggested that high proportions of exchangeable fractions in metals may give high dissolution rates at Deokeum. In both microcosms of Siheung and Deokeum, redox differences between surface and subsurface of paddy soils were maintained during the flooded period of 18 weeks. Siheung soil had neutral to alkaline pH conditions, while strongly acidic conditions and high Eh values were found at the surface soil of Deokeum. The concentrations of dissolved Fe and Mn were higher in the subsurface pore waters than in interface and upper waters from both microcosms, indicating reductive dissolution under reducing conditions. On the contrary, dissolved Pb and Zn had high concentrations at the surface under oxidizing conditions. From the Siheung microcosm, release of dissolved metals into upper waters was decreased. presumably by the trap effect of Fe- and Mn-rich layers at the interface. However, in the Deokeum microcosm, significant amounts of Pb and Zn were released into upper water despite the relatively lower contents in raw paddy soil, and seasonal variations in the chemical fractionation of metals were observed between flooded and drained conditions. Under acidic conditions, rice may uptake high amounts of metals from the surface of paddy soils during the flooded periods, and increases of exchangeable phases may also increase the bioavailability of heavy metals in the drained conditions.

• 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.

• Proceedings of the Korean Society of Crop Science Conference
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• 2004.04a
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• pp.204-205
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• 2004

• Proceedings of the Korean Society of Crop Science Conference
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• 2005.08a
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• pp.75-87
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• 2005

Remote sensing(RS)- and geographic information system(GIS)-based information management to measure and assess agri-environment schemes, and to quantify and map environment indicators for nature and land use, climate change, air, water and energy balance, waste and material flow is in high demand because it is very helpful in assisting decision making activities of farmers, government, researchers, and consumers. The versatility and ability of RS and GIS containing huge soil database to assess agricultural environment spatially and temporally at various spatial scales were investigated. Spectral and microwave observations were carried out to characterize crop variables and soil properties. Multiple sources RS data from ground sensors, airborne sensors, and also satellite sensors were collected and analyzed to extract features and land cover/use for soils, crops, and vegetation for support precision agriculture, soil/land suitability, soil property estimation, crop growth estimation, runoff potential estimation, irrigated and the estimation of flooded areas in paddy rice fields. RS and GIS play essential roles in a management and monitoring information system. Biosphere-atmosphere interection should also be further studied to improve synergistic modeling for environment and sustainability in agri-environment schemes.

• Korean Journal of Environmental Agriculture
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• v.35 no.1
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• pp.32-38
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• 2016

BACKGROUND: Our study aims to investigate the impact of temperature on the abundance and structure of soil microbial community in a temperature gradient tunnel.METHODS AND RESULTS: To investigate the interaction between temperature and input of C and N, rice straw and urea were applied to the study plots, respectively. We also studied the impact of plants by comparing plots cultivated with rice and unplanted plots. Soil microbial response was measured using the phospholipid fatty acid (PLFA) analysis. Soil chemical properties, including pH and ammonia and phosphate concentrations were influenced by warming and material addition. Microbial PLFA was partially influenced by material inputs, and actinomycetes PLFA was decreased by warming. In cultivated rice plots, an increase in the carbon to nitrogen ratio illustrated the effect of plant on microbiota caused by carbon addition through the root residues. Results from the principal component analysis of PLFA data showed that warmed and control plots applied with rice straw could be separated by principal component analysis.CONCLUSION: Our results suggest that plant influence both the microbial community structure and abundance, and temperature change has a minimal impact on soil microorganisms in flooded soil.