• Korean Journal of Environmental Agriculture
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• v.1 no.1
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• pp.59-64
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• 1982

Studies on the effect of soil moisture, different seasons, harvesting periods and nitrogen application on the nitrate content of radish(Raphanus sativus L. var. niger(Mill.) S. Kerner) were carried out in pot and green house. The results are as follows; The low level of soil moisture leads to an increased nitrate accumulation in radish root. The nitrate content was found to be higher in spring crops and lower in summer ones. It was decreased during harvesting period. The application of nitrogen fertilizer increased the nitrate content in radish root. We found the highest content in petioles with lesser content in roots and leaf blades in that order. The multiple regression analysis and the nutritional value of nitrate content in radish were discussed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.3
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• pp.223-231
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• 1994

To investigate effects of water stress on leaf water potential, nitrate reductase activity and abscisic acid content, Paldalkong, Saealkong and Danyeobkong were subjected to water stress by polyethyene glycol(PEG, MW=6,000) in the water culture and withholding irrigation in soil culture. Leaf water potential and nitrate reductase activity decreased with increaseing of PEG concentration in the water culture. These were higher at 3rd and 5th leaf stage than at 1st leaf stage. Leaf water potential showed no significant differance among the varieties, but nitrate redutase activity was higher in Paldalkong than in Saealkong and Danyeobkong. Leaf water potential and nitrate reductase activity decreased approximately 2.2 times (-1.67 MPa/-0.75MPa) and 47%(3.1${\mu}$ mole nitrite/g.DW/hour/15.9${\mu}$ mole nitrite/g.DW/hour) to control, respectively, after 3 days from water stress treatment in the soil culture. According to increasing PEG concentration, abscisic acid content increased in the water culture and was higher at 5th leaf stage than at 1st and 3rd leaf stage. Paldalkong showed the highest abscisic acid content. Abscisic acid content increased approximately 1.7 times (9.9nmole/g.DW/5.7nmole/g.DW) compared to the control after 3 days from water stress treatment in the soil culture.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.385-390
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• 2014

To evaluate the impact of nitrogen fertigation on crop growth and $NO_3$-N concentration in the soil solution, field experiment for cucumber cultivation during spring and fall season were carried out in on-farm located in Byeongcheon-myeon, Chunan-si, Chungcheonnam-do. Supplying nitrogen of 120-150 mg/L by fertigation device into soil per week reached to maximum yields of cucumber fruits. However, cucumber growth did not show any significant difference between nitrogen levels. Nitrogen supply of 400 mg/L, highest N levels, did not affect cucumber growth. Difference between green values of cucumber leaves using RGB scores were closely related with cucumber yields, and therefore, this results suggests that green values of cucumber leaves could be used as a way of determining the application rates of nitrogen for cucumber cultivation period under fertigation system.

• Applied Biological Chemistry
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• v.51 no.1
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• pp.1-5
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• 2008

Salt accumulation in soils of greenhouse due to the massive application of nitrogen fertilizers causes salt stress on the various crops, a serious problem in domestic agriculture. Since the majority of the salinity is nitrate, the excess nitrate should be removed; therefore, a bacterial strain having high capacity of nitrate uptake and identified as Enterobacter amnigenus GG0461 was isolated from the soils of greenhouse. Optimum conditions for the bacterial growth and nitrate uptake were investigated. GG0461 was able to grow without nitrate; however, nitrate facilitated the growth. The rate of nitrate uptake increased at alkaline pH and both growth and nitrate uptake were maximal at pH 8-9. When the initial pH of culture medium was increased to pH 8 or 9, it was decreased to neutral upon bacterial growth and nitrate uptake. These results imply that the major factor mediating bacterial nitrate uptake is a nitrate/proton antiporter. The fact was supported by the effect of nitrate addition in the absence of nitrate, since the addition of nitrate greatly increased the nitrate uptake and rapidly decreased pH of media.

• Journal of Environmental Science International
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• v.16 no.11
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• pp.1219-1223
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• 2007

The removal of nitrogen compounds from a wastewater is essential and it is often accomplished by bio-logical process. An aerobic nitrate-removing bacterium was isolated from a municipal sewage treatment plant and soil. On the basis of its morphological, cultural and physiological characteristics and 16S rRNA sequencing data, this strain was identified as Pseudomonas fluorescens, and named as P. fluorescens K4. The optimal conditions of the initial pH and temperature of media for its growth were $7.0{\sim}8.0$ and $30^{\circ}C$, respectively. P. fluorescens K4 was able to remove 99.9% of nitrate after 24 h in a culture. The strain could grow with a nitrate concentration up to 800 mg/l and was able to remove 99.9% of nitrate after 104 h of incubation. The optimal electron donor was sodium citrate for a nitrate removal. The strain K4 showed a capability of a complete nitrate removal when the initial C/N ratio was 1.0. An effect of the initial seed concentration was observed for a cell of 10% (v/v) for a nitrate removal. Especially P. fluorescens K4 could completely remove 200 mg/l ammonium for 3 days.

• Korean Journal of Organic Agriculture
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• v.7 no.2
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• pp.125-151
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• 1999

After the release of facts that the high nitrate contents in vegetables by Korean organic farming, organic farmers were recommended by Korean Organic Farmer Association to apply 20t/ha compost while they applied before as much as they could, sometimes even more than 100t/ha. This study was aimed to check the safety of Korean organic product in terms of nitrate content. Current nitrate content in leaf and root vegetables by 3 different farming systems(organic farming, conventional farming, greenhouse farming) were monitored and furthermore it was compared with previously published another data in Korea to find out any changes among the monitored years(1993-1999). Current nitrate content in chinese cabbage, lettuce and kale became less compare to those of the beginning of monitoring, and especially those cultivated organic farming got the lowest value while previous organic vegetables at beginning of 90's showed the higher value than those cultivated in greenhouse. This decrease in organic vegetables was affected by less application rate of organic fertilizer than before at 20t/ha. But the nitrate level by organic farming was still higher compare to those cultivated by conventional farming in open field, since currently monitored organic vegetables were cultivated basically in greenhouse condition. It shows the organic farmer the necessity of transfer their farming site and condition from greenhouse to open field in order to decrease of its high level of nitrate caused long-term application and slow release characteristics of organic fertilizer. It was concluded the adoption of soil nitrate test to recommend a organic farmer the exact application rate for need of crop growth. Additionally the mechanism of lower nitrate accumulation in rice and fruit vegetables were also discussed in the paper.

• Korean Journal of Soil Science and Fertilizer
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• v.19 no.1
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• pp.9-13
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• 1986

An experiment on strawberry (Fragaria Grandflora EHRH) was conducted in order to compare the effect of two compound fertilizers made for this crop, by Kyonggi Chemical Crop. LTD. with that of muriate of potash, sulfate of potash and ammonium nitrate in a farmer's vinylhouse during the winter period of 1984 to 1985. Results obtained are as follows; 1. The effect of compound fertilizers on the growth, number of inflorescences and yield of strawberry showed no significant difference from the effect of muriate of potash, sulfate of potash and ammonium nitrate. But the former increased the content of reduced, and total sugars soluble in diluted acid in the juice of strawberry. 2. As a whole, sulfate of potash increased sugar content in strawberry juice more than muriate of potash, which became the reason to increase the sugar content in the strawberry juice harvested from the compound fertilizer plots.

• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.1-10
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• 2022

Most wells developed in Jeju island before the enactment of the Groundwater Management Ordinance in 2002 are vulnerable to aquifer contamination due to inflow of upper groundwater having the high concentration of nitrate nitrogen, likely due to incomplete grouting in upper section of the wells. Although these wells require entire reinstallation, it is often necessary to rehabilitate the existing wells due to various constraints. Therefore, to identified the inflow section of contaminants, the thermal level sensor (TLS) technique was firstly applied for three wells, which enables to monitor temperature variations in every 50 cm depth. Then, the grouting material was injected to the upper section to prevent the inflow of upper contaminated groundwater into the entire aquifer. By applying TLS technique, it was found that the temperature deviations in the upper groundwater inflow section decreased sharply. Moreover, both the change in the concentration of nitrate nitrogen in the rainy/dry seasons and the average concentrations were found to decrease rapidly after grouting material injection. Consequently, the application of TLS proposed in the study turned out to be appropriate to prevent aquifer contamination.

• Agricultural and Biosystems Engineering
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• v.4 no.1
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• pp.28-33
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• 2003

Achievements in the real-time soil spectro-photometer are: an improved soil penetrator to ensure a uniform soil surface under high speed conditions, real-time collecting of underground soil reflectance, getting underground soil color images, use of a RTK-GPS, and all units are arranged for compactness. With the soil spectrophotometer, field experiments were conducted in a 0.5 ha paddy field. With the original reflectance, averaging and multiple scatter correction, Kubelka-Munk (KM) transformation as soil absorption, its 1st and 2nd derivatives were calculated. When the spectra was highly correlated with the soil parameters, stepwise regression analysis was conducted. Results include the best prediction models for moisture, soil organic matter (SOM), nitrate nitrogen (NO$_3$-N), pH and electric conductivity (EC), and soil maps obtained by block kriging analysis.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.3
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• pp.275-283
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• 1987

In order to find out the effectiveness of nitrogen fixation in rhizobia-legume symbiotic relationship, ecological and physiological characteristics of indigenous rhizobia distributed in Korean soils, that is, dissimilatory nitrate reduction patterns of indigenous soybean rhizobia isolated from four different soils, and differences in one-and two-dimensional polyacrylamide gel electrophoretic pattern of proteins among the each subgroups of Bradyrhizobium japonicum and Rhizobium fredii, were investigated. The results were summarized as follows: 1. The indigenous soybean rhizobia isolated from four different soils could be classified into 4 groups depending on growth rate and dissimilatory nitrate reduction pattern, that is, $S_1$ (slow-grower; Bradyrhizobium japonicum and nitrate denitrifier), $S_2$ (slow-grower; Bradyrhizobium japonicum and nitrate respirer), $F_1$ (fast-grower; Rhizobium fredii and denitrifier), and $F_2$ (fast-grower; Rhizobium fredii and nitrate respirer). 2. The population ratio of fast- to slow-growing R. japonicum was 39% to 61%, and the ratio of denitrifier to nitrate respirer was 31% to 69% and 89% to 11% in fast and slow-grower, respectively. Some differences were observed between fast- and slow-growing R. japonicum but no significant difference was observed between denitrifier and nitrate respirer within same growth type by one and two dimensional SDS-polyacrylamide gel electrophoretic patterns.