• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.3-3
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• 2017

The question of how to establish sustainable agricultural systems has become as prominent as questions related to water, energy and climate change. High input/high output agriculture has brought with it many adverse effects; the massive deterioration of soil and water in both quantity and quality, increased greenhouse gas emissions and an increased prevalence of unsafe foods. Additionally, urbanization and climate change has worsened the shortage of farmland and reduced the supply of agricultural water. Given these challenges, maintaining, conserving and efficiently using agri-environmental resources, through fostering of sustainable agriculture, have emerged as key tasks in solving these problems. What is needed therefore is research, based on systematic and comprehensive empirical analyses, that can propose plans and methods for establishing an appropriate sustainable agricultural system. The empirical analysis of sustainable agricultural system is approached separately from economic, environmental and social aspects. An analysis of environment effect reveals that the available phosphate level is 1.3~2.1 times greater than the optimal amount in rice paddies, upland fields and orchards. Further examination has revealed that the excess nutrient is polluting both ground water and surface water. Analytical results for economic feasibility show that factors of production have been invested heavily in the rice crop. Under these conditions, sustainable agriculture, including low-input agriculture, appears to be a possible alternative that will facilitate simultaneous improvements in both economic feasibility and environment effects. Analysis results for sociality reveal that social factors include the value of producer, association and interior networks. Social conditions are comprised of leadership, consumers' awareness, education and conflict solutions. In addition, analysis as to the degree investments contribute to improving agricultural value added has revealed that the direct payment program is the most effective instrument. Experts confirm that economic feasibility can be improved by scientific and well-reasoned nutrient management on the basis of soil testing. Farmers pointed to 'economic factors' as being the largest obstacle to switching to the practice of sustainable agriculture. They also indicate 'uncertainty with regards to sustainable agriculture technology' as an impediment to practicing sustainable agriculture. Even so, farmers who believe environmental and regional issues to be the most pressing problems have expanded their practice of sustainable agriculture. The keys to establishing sustainable agriculture system are classified into the following four aspects. Firstly, from an economic aspect, the research indicates that agricultural policy needs to be integrated with environmental policy and that the function of market making based on the value chain needs to be revitalized. Secondly, from an environmental aspect, there is a need for an optimal resource management system to be established in the agricultural sector. In addition, sustainable agriculture practice will need to be extended with attendant environmentally-friendly and sustainable intensive technology also requiring further development. Thirdly, from a social aspect, green agriculture management needs to be fostered, technology and education extended, and social conflict mediated. Lastly, from a governance aspect, it will be necessary to strengthen good governance, assign and share suitable roles and responsibilities, build a cooperation system and utilize community supported agriculture.

• Korean Journal of Organic Agriculture
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• v.23 no.4
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• pp.813-827
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• 2015

This study was conducted to evaluate the effect of organic inputs on soil properties in a newly reclaimed organic soils. The soil of the experiment site was very low in soil fertility and the physico-chemical properties were poor. Several organic input treatments with different source of nutrient were placed, including compost in combination with green manures for organic agricultural practices, chemical fertilizers for conventional agricultural practices, and control without fertilizer. The experiment was conducted with continuous cropping system during 3 years. The chemical properties concentration in compost+green manure treatment was increased continually compare to control and chemical fertilizer treatment, and closed to the recommended rate of fertilizer. The organic matter value for compost+green manure treatment was increased from 0.86~0.96% to 2.00~2.29% by continuous nutrient supply of compost and green manure. However, further investigation on increasing of organic matter value for 3 years is necessary to monitor carefully during the long-term because it will help to clarify the all mechanisms of organic matter on organic input application way. The available phosphate value for compost+green manure treatment was generally increased from 21.9~27.1 mg/kg to 182.0~394.1 mg/kg. In case of exchange cation, the concentration for compost+green manure treatment was increased during 2 years within the range to the recommended rate of fertilizer, however, it is expected to cause a rather over supply for 3 years.

• Korean Journal of Environment and Ecology
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• v.25 no.4
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• pp.573-580
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• 2011

Litter production, nutrient concentration of each component of litterfall and amount of nutrients input to forest floor via litterfall were investigated for four years from May 2005 through April 2009 in Quercus variabilis forest at Mt. Worak National Park. Amount of litterfall in 2005, 2006, 2007, 2008 were 5.181, 5.372, 5.314, 5.361 ton $ha^{-1}yr^{-1}$, respectively. Average amount of litterfall for four years was 5.307${\pm}$0.09 ton $ha^{-1}yr^{-1}$. Average percentage of leaf litter, branch and bark, reproductive organ and the miscellaneous for four years were 67.5${\pm}$1.9, 13.3${\pm}$0.8, 10.1${\pm}$0.5 and 9.1${\pm}$1.2%, respectively. Average amount of N, P, K, Ca and Mg returned to forest floor via litterfall for four years in this Q. variabilis forest were 44.47${\pm}$6.70, 2.50${\pm}$0.25, 12.26${\pm}$0.30, 17.23${\pm}$2.32 and 9.56${\pm}$0.54 kg $ha^{-1}yr^{-1}$, respectively.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.340-345
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• 2017

Carrot leaves have many nutrients as well as roots, which will increase the demand for carrot leaves in the future. This study was carried out by dividing into two stages: high temperature and low temperature periods, in order to investigate the possibility of cultivation of carrot leaves and the composition and EC of the nutrient solution for growth and quality of carrot leaves. Composition of nutrient solution($NO_3-N:16.0$, $NH_4-N:1.0$, P: 1.0, K: 11.0, Ca: 2.0, Mg: 1.0, $SO_4-S:1.0mM{\cdot}L^{-1}$) developed by analysis of plant. In the high temperature range (From June $29^{th}$ to Sep. $8^{th}$, 2016), the concentration of the developed nutrient solution (JNU) were 1.0, 2.0, 3.0, and $4.0dS{\cdot}m^{-1}$ and the concentration of nutrient solution of Japanese Horticultural Station(JHS) $2.0dS{\cdot}m^{-1}$ was used for comparison. In the low temperature range (From Dec. $31^{st}$, 2015 to Feb. $29^{th}$, 2016), the concentration of the developed nutrient solution 1.0, 2.0, and $3.0dS{\cdot}m^{-1}$ were used. Growth was investigated in root fresh and dry weights, shoot fresh and dry weights, leaf number, and leaf area of carrot. In the high temperature range, the leaf area and shoot fresh and dry weights were good at 1.0 and $2.0dS{\cdot}m^{-1}$. The sugar content of the root was the highest at the EC $2.0dS{\cdot}m^{-1}$, and the chlorophyll content was the highest at the EC $4.0dS{\cdot}m^{-1}$. In the low temperature range, The shoot fresh and dry weights were the highest at EC 1.0 and $2.0dS{\cdot}m^{-1}$. There was no significant difference in sugar content and chlorophyll content. As a result, from the viewpoint of growth and quality of carrot, it is good to cultivate EC 1.0 and $2.0dS{\cdot}m^{-1}$ in high temperature period and low temperature period, but EC $1.0dS{\cdot}m^{-1}$ is economical perspective such as fertilizer input.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.255-268
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• 2012

Nonpoint source pollution has become a concern for water quality in the Han River system, especially during the high runoff events during the monsoon season. The patterns in nonpoint source runoff the relationships with land use, rainfall intensity, and stream nutrients concentrations were surveyed in 19 streams in the Han River watershed. The results show that the magnitude of NPS inputs of nutrients and sediment in the Han River watershed are of a serious concern. In the South Han River watershed, event mean concentrations (EMC) for biochemical oxygen demand (BOD), suspended sediment (SS), dissolved organic carbon (DOC), dissolved total phosphorus (DTP), total nitrogen (TN) Nitrate ($NO_3$-N) and total phosphorus (TP) were $1.94mg{\cdot}L^{-1},\;251mg{\cdot}L^{-1},\;2.75mg{\cdot}L^{-1},\;0.076mg{\cdot}L^{-1},\;2.82mg{\cdot}L^{-1},\;2.40mg{\cdot}L^{-1}$ and $0.232mg{\cdot}L^{-1}$, respectively. In the North Han River watershed, EMCs for BOD, SS, DOC, DTP, TN, $NO_3$-N and TP were $1.34mg{\cdot}L^{-1},\;172mg{\cdot}L^{-1},\;2.63mg{\cdot}L^{-1},\;0.032mg{\cdot}L^{-1},\;1.97mg{\cdot}L^{-1},\;1.55mg{\cdot}L^{-1}$ and $0.148mg{\cdot}L^{-1}$, respectively. The specific export coefficients of nutrient and sediments were much higher than those of other reports. Our study also found that the proportion of agricultural field area was significantly correlated with the EMCs for nutrients. Therefore, efforts to reduce NPS loading must focus on agricultural practices in the watershed. The relationships between land use and nutrient and sediment export found in this study can be used to derive estimates of runoff coefficients for agricultural field and as input data for modeling works and to develop total maximum daily load and best management practices in the Han River watershed.

• Korean Journal of Environment and Ecology
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• v.32 no.1
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• pp.23-29
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• 2018

The litter production, the nutrient concentration of each component of litterfall, and the amounts of nutrient into the forest floor via litterfall were assessed for 5 years from January 2009 through December 2013 in a Pinus densiflora forest in Mt. Worak National Park. The average amounts of leaf litter, branch and bark, reproductive organs(flowers and cones), and miscellaneous categories for 5 years were $1.940{\pm}0.21$, $0.505{\pm}0.15$, $0.259{\pm}0.09$, and $0.737{\pm}0.14t\;ha^{-1}yr^{-1}$, respectively. The average percentage of leaf litter, branch and bark, reproductive organs and miscellaneous categories for 5 years were 56.4, 14.7, 7.5, and 21.4%, respectively. The amounts of total litterfall in 2009, 2010, 2011, 2012, and 2013 were 2.810, 3.796, 3.268, 3.284, and $4.045ton\;ha^{-1}yr^{-1}$, respectively. The average amounts of litterfall for 5 years were $3.441{\pm}0.4ton\;ha^{-1}yr^{-1}$. The average amounts of N, P, K, Ca, and Mg returned to the forest floor via litterfall for 5 years in this Pinus densiflora forest were $22.73{\pm}4.92$, $1.05{\pm}0.42$, $4.26{\pm}1.69$, $8.48{\pm}4.62$, and $2.42{\pm}1.01kg\;ha^{-1}yr^{-1}$, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.5
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• pp.344-355
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• 2003

Korea is one of those countries that have very high usage rates of chemical fertilizers per unit area of cropland. To reduce the fertilizer application rate, a variety of agricultural polices has been introduced since the 1990s. In this study, fertilizer usage was surveyed on the farm base throughout the country in 1999, and the data were compared with those of 1992. Organic fertilizer application rates were decreased in most cereal crops with time pass, but maintained similar levels in vegetables grown in plastic-film houses and in upland soils. Chemical fertilizer application rates were decreased in most of the cereal crops and vegetables surveyed; however, this reduction was concentrated in phosphate and potassium usage, but not in nitrogen. In spite of this decrease, the fertilizer application levels to most crops were maintained at levels much higher than recommended. In the nutrient balance, which was calculated from the difference between input (chemical and organic fertilizers) and output (agricultural products), the nitrogen nutrient surplus did not decrease; however, phosphate and potassium decreased by 21% and 13%, respectively, in 1999 compared with 1992. To reduce fertilizer utilization and to conserve environment, further reduction of fertilizer application is essential.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.1094-1099
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• 2012

Green manure cultivation affects soil productivity and nutrient conservation in paddy soil at winter season. This study was to evaluate nitrogen behavior released from chinese milk vetch (CMV) as green manure by using stable $^{15}N$ trace during rice cultivation. The CMV used in the experiment was 29.9 of C/N ratio and 14.1 g N $kg^{-1}$ ($^{15}N$ 0.388 atom % excess) and was applied at rates of 10 and $30Mg\;ha^{-1}$ in pot of 1/2000a size. Rice growth and N uptake increased with higher levels of CMV application at harvesting stage. Among total N uptake, 14.6 and 26.8 % of nitrogen was released respectively from the two different rates of CMV application. Stable $^{15}N$ recovery by rice biomass was 60%, 54% to the $^{15}N$ input, respectively, of CMV application, which decreased in order of grain, root, and straw of rice biomass. Total N content in the soil after rice harvest was 1.9 and 2.1 g N $kg^{-1}$, respectively, with increasing N input by the different rates of CMV application and the rate of $^{15}N$ recovery derived from CMV in the soil was 3.8 and 4.8 %, respectively. N input by CMV application induced rice growth and productivity during rice cultivation. However, it might need proper managements to reduce N loss because about 36-41 % of nitrogen was lost from N input by CMV application.

• Proceedings of KOSOMES biannual meeting
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• 2003.05a
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• pp.191-200
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• 2003

Gunsan coastal area is one of region increasing pollution problems. One of the most important factors that cause eutrophication is nutrient materials containing nitrogen and phosphorus which stem from excreation of terrestial sources. At this study, the three-dimensional numerical hydrodynamic and ecosystem model, which was developed by Institute for Resources and Environment of Japan, were applied to analyze the processes affecting the eutrophication. The residual currents, which were obtained by integrating the simulated tidal currents over 1 tidal cycle, showed the presence of a typical. Density driven currents were generated westward at surface and eastward at the bottom in Geum estuary area where the fresh waters are flowing into. The ecosystem model was calibrated with the data surveyed in the field of the study area in annual average. The simulated results of DIN were fairly good coincided with the observed values within relative error of 32.39%. correlation coefficient(r) of 0.99. In the case of DIP, the simulated results were fairly good coincided with the observed values within relative error of 24.26%, correlation coefficient (r) of 0.82. The simulations of DIN and DIP concentrations were performed using ecosystem model under the conditions of 20 ∼ 80% pollution load reductions from pollution sources. In study area, concentration of DIN and DIP were reduced to 20∼80% and under 10% in case of the 80% reduction of the input loads from fresh water respectively. But pollution loads from sediment had hardly affected DIN and DIP concentration. For the environment management of coastal areas, in case of Kunsan area, the most important pollution sources affecting eutrophication phenomenon were found to be the input loads from fresh water.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.3
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• pp.213-236
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• 2001

The ionic composition of soil solution is related to a nutrient uptake by plant. Many models for estimating ionic composition of solution have been developed, and most of them have been used for calculating a content of mineral and ionic species in a geochemical point of view. An approximation model considering both cation and anion in soil solution was developed. Variables such as pH, Eh, EC, cations(K, Ca, Mg. Na, Fe, Mn, Al, $NH_4{^+}$), anions(Si, S, P, CY, $NO_3{^-}$, $HCO_3{^-}$ and chemical equilibria of ionic species in soil solution were input into Excel sheet. The activities of soluble ion, ionpairs and complexes of input element were estimated by Newton-Raphson method using conditional equilibrium constant calculated by Davies equation and special models. Equilibrium contents of insoluble minerals and complexes were also calculated.