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Featured researches published by Young-Dae Choi.


The Korean Journal of Ecology | 2003

Distribution of Heavy Metals in Soils of Shihwa Tidal Freshwater Marshes

Seok-In Yun; Woo-Jung Choi; Young-Dae Choi; Seung-Heon Lee; Sun-Ho Yoo; Eun Ju Lee; Hee-Myong Ro

Shihwa tidal freshwater marsh was constructed recently to treat pollutants entering Shihwa lake. In this study, we examined the spatial and temporal patterns of heavy metal accumulation in soils of Shihwa marsh and sought correlations between several soil variables (pH, electrical conductivity, organic matter, and acid ammonium oxalate-extractable Fe and Al contents) and the heavy metal concentration of soils. Surface soil samples (0∼20 cm) were collected in June 2000, November 2000, and July 2001, and were analyzed for heavy metals (Zn, Cd, Pb, Cu, Cr, As, and Hg) and soil chemical properties. The neutral pH and water-saturated conditions of Shihwa marsh appeared to favor immobilization of heavy metal through adsorption onto soils. The concentrations of heavy metal (especially Zn, Cu, and Cr) in soils of Shihwa marsh increased along the sampling occasions, suggesting that soils of Shihwa marsh serve as a sink of heavy metal. Among the sub-marshes, metal concentrations were highest in Banweol high marshes and lowest in Samhwa marshes. The temporal and spatial variations in the heavy metal concentrations of soils were correlated positively with organic matter and oxalate extractable Fe and Al contents, but negatively with electrical conductivity. These results suggest that organic matter and hydrous oxide of Fe/Al may playa key role in removing heavy metals in soils of Shihwa marsh, and that heavy metal removing capacity would increase with desalinization. However, the removal patterns of heavy metal by reeds warrant further studies to evaluate the total removal capacity of heavy metals by Shihwa marsh.


Korean Journal of Soil Science and Fertilizer | 2011

Stress Day Index to Predict Soybean Yield Response by Subsurface Drainage in Poorly Drained Sloping Paddy Fields

Ki-Yuol Jung; Eul-Soo Yun; Chang-Young Park; Jae-Bok Hwang; Young-Dae Choi; Ki-Do Park

There are considerable areas of wet paddy fields in Korea that requires improvement of its drainage system. In poorly drained sloping paddy fields, upland crops can be damaged by either rainfall or capillary rise of the water table caused by percolating water beneath the upper fields during summertime rainy season. The purpose of this study is to evaluate excess water stress of soybean yield by drainage systems. Four drainage methods namely open ditch, vinyl barrier, pipe drainage and tube bundle were installed within 1-m position at the lower edge of the upper paddy fields. Stress Day Index (SDI) approach was developed to quantify the the cumulative effect of stress imposed on a soybean yield throughout the growing season. SDI was determined from a stress day factor (SD) and a crop susceptibility factor (CS). The stress day factor is a measure degree and duration of stress of the (SEW30). The crop susceptibility factor (CS) depends of a given excess water on crop stage. The results showed that SDI used to represent the moisture stress index was most low on the pipe drainage 64.75 compared with the open ditch 355.4, vinyl barrier 271.55 and tube bundle 171.55. Soybean grain yield increased continuously with the rate of 3% in Vinyl Barrier, 32% in Pipe Drainage and 16% in Tube Bundle.


Korean Journal of Weed Science | 2012

Effects of Cover Crops and Sowing Methods on Weed Occurrences and Growth and Yield of Sorghum (Sorghum bicolor)

Seung-Ho Jeon; Eul-Soo Yun; Chang-Young Park; Jae-Bok Hwang; Ki-Youl Jung; Young-Dae Choi; Hyun-Ju Kim; Sang-In Shim

This study was conducted to evaluate the weed suppressing effects of different cropping system including hairy vetch (Vicia villosa) and rye (Secale cereale) cover crops, polyethylene plastic film, and transplanting film mulching in direct sowing and transplanted sorghum field in 2011. Crop growth and development and weed occurrences in the fields were examined to know the efficiency of proposed cropping system. In polyethylene film mulching treatment, heading date of sorghum was earlier by 3 days than control, on the other hands, rye cover crop mulching delayed heading date by 11 days. Besides the effect of cover crop on the heading of sorghum, the residues changed growth characteristics. Plant height of sorghum was increased by 27.3% at hairy vetch treatment although it was reduced by 47.5% in the rye cover crop treatment. Hairy vetch treatment showed beneficial effects on sorghum growth reduced the occurrences of grasses and broadleaf weeds to 84% and 96%, respectively, as compared to control in sorghum fields. While rye cover crop treatment showed poor sorghum growth reduced less strongly grasses and broadleaf weeds by 35% and 71%, respectively. At harvest, yield of sorghum was greater in order of hairy vetch cover crop > polyethylene film mulching > rye cover crop control in both transplanted and direct sown fields.


Korean Journal of Soil Science and Fertilizer | 2012

Characteristics of Nutrient Uptake and Stubble Regrowth of Grain Sorghum in Plastic Film House

Eul-Soo Yun; Ki-Yeul Jung; Chang-Yeong Park; Jae-Bog Hwang; Young-Dae Choi; Seung-Ho Jeon

This study was conducted to get the basic information for absorb enhancement of accumulated soil nutrients in plastic film house. The grain sorghum (Sorghum bicolor L.) was sowing in plastic film house which soil nutrient accumulated moderately and was cutting at major growth period of sorghum. We were analyzed the regrowth pattern, biomass due to cutting time and amount of plant nutrient of grain sorghum. The obtained results were as follows. The heading date after cutting of sorghum in plastic film house was came to about 35 days. The accumulated of plant height were the longest as 379.4 cm in cutting at milk stage. The total biomass of sorghum in cutting at heading stage was 1.73 ton in cutting at heading stage. The high grain yields were produced with non-cutting and cutting at 10 leaves stage as 75~113 kg but the lowest grain yields were the cutting plots at booting stage as below 24 kg . The content of nutrient in sorghum plant was low as progress of growth. The concentrations in aboveground sorghum due to plant parts was in order to leaves > panicle > stalk. The nitrogen content of sorghum was 0.6~0.7% in stalk, 1.5~1.6% in panicle and 1.8~2.3% in leaves. The amount of nutrient absorbed in sorghum was 4.2 kg in nitrogen, 1.7 kg phosphorus and 7.7 kg in potassium and the absorbing different by cutting time in order to booting > non-cutting > panicle formation milk ripe > 10 leaves stage.


Korean Journal of Soil Science and Fertilizer | 2012

Variation of Soil Physical Characteristics by Drainage Improvement in Poorly Drained Sloping Paddy Field

Ki-Yuol Jung; Eul-Soo Yun; Chang-Young Park; Jae-Bok Hwang; Young-Dae Choi; Seung-Ho Jeon; Hwang-A Lee

The lower portion of sloping paddy fields normally contains excessive moisture and the higher water table caused by the inflow of ground water from the upper part of the field resulting in non-uniform water content distribution. Four drainage methods namely Open Ditch, Vinyl Barrier, Pipe Drainage and Tube Bundle for multiple land use were installed within 1-m position from the lower edge of the upper embankment of sloping alluvial paddy fields. This study was conducted to evaluate soil physical characteristics by drainage improvement in poorly drained sloping paddy field. The results showed that subsurface drainage by Pipe Drainage improves the productivity of poorly drained soils by lowering the water table and improving root zone soil layer condition. In an Pipe drainage plot, soil moisture drained faster as compared to the other drainage methods. Infiltration rate showed high tendency to Piper Drainage method about than in Open Ditch method . And Similarly soil water and degree of hardness and shear strength phase of soil profile showed a tendency to decrease. From the above results, we found that when an subsurface drainage was established with at 1m position from the lower edge paddy levee of the upper field in sloping poorly drained paddy fields Pipe Drainage was the most effective drainage system for multiple land use.


Korean Journal of Soil Science and Fertilizer | 2012

Effect of Soil Compaction Levels and Textures on Soybean (Glycine max L.) Root Elongation and Yield

Ki-Yuol Jung; Eul-Yoo Yun; Chang-Young Park; Jae-Bok Hwang; Young-Dae Choi; Seung-Ho Jeon; Hwang-A Lee

Soil compaction is one of the major problems facing modern agriculture. Overuse of machinery, intensive cropping, short crop rotations, intensive grazing and inappropriate soil management leads to compaction. This study was carried out evaluate of the effects soil texture and different compaction levels within the soil profile on the soybean root growth and productivity. The soybean plants were grown in cylinder pots using three different soil textures (clay, fine loamy and coarse loamy) compacted at different compaction levels (1.25, 1.50, 1.75, and 2.00 MPa). Results revealed that soybean development is more sensitive on penetration resistance, irrespective of soil type. Soybean yield and root weight density significantly decreases with increasing levels of soil compaction in both clayey and fine loamy soils, but not in coarse loamy soil. The highest root weight density was recorded in coarse loamy soils, followed by fine loamy and clay soils, in descending order. The root growth by soil compaction levels started to decline from 1.16, 1.28 and 1.60 MPa for clay, fine loamy and coarse loamy soils. Soybean production in the field experiment decreased about 30% at compacted sub-soils compared to undisturbed soils.


Korean Journal of Weed Science | 2011

Yearly Variation of Ecological Traits of Weed Flora on Soils Having Different Drainage Property

Jae-Bok Hwang; Eul-Soo Yun; Ki-Youl Jung; Chang-Young Park; Young-Dae Choi; Yong-Hwan Lee; Min-Hee Nam

This survey of weed population by different soil moisture with paddy-upland rotation was conducted to investigate information on weed flora and its ecology between two years. Weed species were assessed in April : 2009, 2010. Soil samples were taken from each study plot to assess the impact soil moisture on the occurrence and abundance of dominance weed species. Soil water of poorly drained field ranged from 10.2~18.2% more than 11.8~14.3% of somewhat poorly drained field. Weeds of fields composed of 19 species belonging to 12 families. Among 12 families, 6 weed species belonged to Compositae (31.6%) were the biggest family, Cruciferae were 2 species (10.5%), and Rubiaceae were 2 species (10.5%), respectively. Youngia japonica had the highest summed dominance ratio(SDR) (97.0%) and followed by Conyza canadensis (92.1%), Galium spurium (35.3%) and Hemistepta lyrata (28.4%) of somewhat poorly drainage in 2009. Artemisia princeps the highest SDR (100%) and followed by Stellaria alsine(55.2%), Y. japonica (38.3%) and Nasturtium officinale (28.5%) of poorly drainage in 2009. And, Stellaria alsine had the highest SDR (86.8%) and followed by Alopecurus aequalis (77.7%), Astragalus sinicus (68.7%) and Y. japonica (46.3%) of somewhat poorly drainage in 2010. S. alsine the highest SDR (93.7%) and followed by A. aequalis (78.6%), Nasturtium officinale (31.3%) and Y. japonica (30.4%) of poorly drainage in 2010. Simpson`s index was calculated to 0.12~0.23, which showed that weed occurrence with different soil moisture in paddy-upland rotation and between years was various. Similarity coefficient between years was 43.0% (2009) and 74.2% (2010), which indicate a low diversity because of the moisture in the agro-ecosystem.


Korean Journal of Weed Science | 2012

Weed Control Technology with Low Concentration Ethanol in Protected Cereal Crop Cultivation

Jae-Bok Hwang; Eul-Soo Yun; Chang-Young Park; Ki-Youl Jung; Young-Dae Choi; Sung-Ho Jeon; Yong-Hwan Lee

ABSTRACT Weed control is of fundamental importance when planting cereal crops, particularly during the establishment phase. Weeds compete for nutrients, water and light, and can severely threaten the survival and early growth of newly planted crops. Field experiment was conducted to evaluate the effect of ethanol treatment on the weed control efficacy in cereal crops in protected vinylhouse. Five treatments like water, 25 L, 50 L, 75 L, and 100 L per m -2 at 2% ethanol were applied and covered with vinyl on 10 days before foxtail millet seeding. After that, foxtail millet seeds were sown on June 20 at 60×10cm planting distance and weed control efficacy was recorded at 30, and 50 days after seeding based on the dry weight. Soil oxidation-reduction potential was recorded -200~-400 ㎷ after treatment 2 days. Weed control efficacy of at 75 L, and 100 L per m -2 was observed 92%, 84% in 2% ETOH, respectively. Yields of foxtail millet at 75 L, and 100 L per m -2 were 1,570 kg ha -1 , 1,230 kg ha


Korean Journal of Soil Science and Fertilizer | 2016

Spatial Analyses of Soil Chemical Properties from a Remodeled Paddy Field as Affected by Wet Land Leveling

Ki-Yuol Jung; Young-Dae Choi; Sanghun Lee; Hyen Chung Chun; Hang-Won Kang

Uniformity and leveled distributions of soil chemicals across paddy fields are critical to manage optimal crop yields, reduce environmental risks and efficiently use water in rice cultivation. In this study, an investigation of spatial distributions on soil chemical properties was conducted to evaluate the effect of land leveling on mitigation of soil chemical property heterogeneity from a remodeled paddy field. The spatial variabilities of chemical properties were analyzed by geostatistical analyses; semivariograms and kriged simulations. The soil samples were taken from a 1 ha paddy field before and after land leveling with sufficient water. The study site was located at Bon-ri site of Dalseong and river sediments were dredged from Nakdong river basins. The sediments were buried into the paddy field after 50 cm of top soils at the paddy field were removed. The top soils were recovered after the sediments were piled up. In order to obtain the most accurate spatial field information, the soil samples were taken at every 5 m by 5 m grid point and total number of samples was 100 before and after land leveling with sufficient water. Soil pH increased from 6.59 to 6.85. Geostatistical analyses showed that chemical distributions had a high spatial dependence within a paddy field. The parameters of semivariogram analysis showed similar trends across the properties except pH comparing results from before and after land leveling. These properties had smaller “sill” values and greater “range” values after land leveling than ones from before land leveling. These results can be interpreted as land leveling induced more homogeneous distributions of soil chemical properties. The homogeneous distributions were confirmed by kriged simulations and distribution maps. As a conclusion, land leveling with sufficient water may induce better managements of fertilizer and water use in rice cultivation at disturbed paddy fields.


Korean Journal of Soil Science and Fertilizer | 2016

Interspecific Differences of the Capacities on Excessive Soil Moisture Stress for Upland Crops in Converted Paddy Field

Ki-Yuol Jung; Young-Dae Choi; Hyen-Chung Chun; Sanghun Lee; Hang-Won Kang

The interspecific estimation for tolerance capacities of upland crop species to excessive soil water stress in paddy field is significant in agricultural practices. Most of upland crops can be damaged by either excessive soil water or capillary rise of the water table during rainy season in paddy fields. The major objective of this study was to evaluate water stress of upland crops under different drainage classes in converted paddy field. This experiment was carried out in poorly drained soil (PDS) and imperfectly drained soil (IDS) of alluvial sloping area located at Toero-ri, Bubuk-myeon, Miryang-si, Gyeongsangnam-do. The soil was Gagog series, which was a member of the fine silty, mixed, nonacid, mesic family of Aeric Endoaquepts (Low Humic-Gley soils). Two drainage methods, namely under Open ditch drainage methods (ODM) and, Closed pipe drainage methods (PDM) were installed within 1-m position at the lower edge of the upper paddy fields. The results showed that sum of excess water days (SWD30), which was used to represent the moisture stress index, was 42 days (the lowest) in the PDM compared with 110 days in the ODM. Most of upland crops were more susceptible to excessive soil water during panicle initial stage on more PDS than on IDS. Yield of upland crops in the PDM was continuously increased by the rate of 15.1% on sorghum, 15.4% foxtail millet, 53.6% proso millet, 49.6% soybean and 47.9% adzuki bean as compared in the ODM. The capacity for tolerance by excessive soil water based on yield of each upland crop in the poorly drained sloping paddy fields was the order of sorghum, soybean, foxtail millet, proso millet and adzuki bean. Therefore, Sorghum is relatively tolerant to excessive soil water conditions and, may be grown successfully in converted paddy field.

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Seung-Ho Jeon

Gyeongsang National University

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Jee-Yeon Ko

Rural Development Administration

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Hang-Won Kang

Rural Development Administration

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Sanghun Lee

Chungnam National University

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Hee-Myong Ro

Seoul National University

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Seok-In Yun

Seoul National University

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Woo-Jung Choi

Chonnam National University

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Yong-Hwan Lee

Seoul National University

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