• Korean Journal of Environmental Agriculture
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• v.9 no.2
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• pp.83-95
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• 1990

This study was conducted to estimate influences of pesticides such as carbofuran[2,3-dihydro-2,2-dimethylbenzofuran-7-yl methyl carbamate] as an insecticide, and pyrazolate [4-(2,4-dichlorobenzolyl)-1,3-dimethyl-5-pyrazolyl-1,3-dimethyl-5-pyrazolyl-p-toluensulfonate], pyrazolate+pretilachlor [2-chlor-2,6-diethyl-N-(n-propoxyethyl) acetanilied] as herbicides on change in numbers of soil microorganisms and pH in planted and unplanted flooded rice paddy soils. The results of weekly investigated change of pH and populations of total bacteria, gram negative bacteria, anaerobic bacteria and fungi after treatments of pesticides were as follows : The change of pH in rice-planted soil gradually decreased in a matter of weeks after treatment with pesticide and the pH increased again from the sixth week, but no change of pH could be observed in nonplanted soil. The total numer of bacteria in the treated plots were slightly less than in the control plot, and the numbers decreased with increasing application rates of pesticides. But the microbial population increased in a matter of days after treatment with pesticide. Number of the gram negative bacteria until the sixth week after treatment of pesticide were fewer than control. The number in the carbofuran-treated plot decreased after a weeks after treatment, but numbers in plots treated with pyrazolate and pyrazolate+pretilachlor increased. The number of anaerobic bacteria in the treated plots were few by comparison with the untreated control, but the number increased after a weeks after treatment with pesticides. The populations of fungi in the carbofuran-treated plot were similar by comparison with the untreated control. The populations in the plots treated with pyrazolate and pyrazolate+pretilachlor decreased in 4 to 5 weeks with increase of application rate, but afterwards increased.

• Korean Journal of Environmental Agriculture
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• v.6 no.1
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• pp.1-6
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• 1987

A pot experiment was conducted to find out the effect of water management on the growth and uptake of arsenic and inorganic nutrients of rice plant at As added soil. The arsenic were added to soil at the levels of As 0, 10, 50, 100 and 150 ppm, respectively. Water management was done with two ways: intermittent irrigation from ten days after transplanting, and continuous submersion until harvest. Higher soil As levels increased As content in plant but reduced growth rate. Aresenic content in plant was considerably reduced with intermittent irrigation compared to continuous submersion. Rice growth showed also same trend. With increasing As levels in soil, N content in plant was increased but P, K, Ca, Mg, $SiO_2$, Fe and Mn content in plant were tend to be decreased. These inorganic nutrients in plant were also much absorbed in continuous submersion compared to intermittent irrigation. Soil pH was slightly increased with increasing As levels in soil while soil Eh has no relationship with soil As levels. On the other hand, soil pH was higher in the treatment of continuous submersion than that of intermittent irrigation but soil Eh showed reverse trend. With increasing As levels in soil, water soluble-As and Ca-As fractions in soil tend to be increased with continuous submersion, but these fractions has no tendency with intermittant irrigation.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.853-860
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• 2012

To estimate potential use of fly ash in reducing $CH_4$ and $CO_2$ emission from soil, $CH_4$ and $CO_2$ fluxes from a paddy soil mixed with fly ash at different rate (w/w; 0, 5, and 10%) in the presence and absence of fertilizer N ($(NH_4)_2SO_4$) addition were investigated in a laboratory incubation for 60 days under changing water regime from wetting to drying via transition. The mean $CH_4$ flux during the entire incubation period ranged from 0.59 to $1.68mg\;CH_4\;m^{-2}day^{-1}$ with a lower rate in the soil treated with N fertilizer due to suppression of $CH_4$ production by $SO_4^{2-}$ that acts as an electron acceptor, leading to decreases in electron availability for methanogen. Fly ash application reduced $CH_4$ flux by 37.5 and 33.0% in soils without and with N addition, respectively, probably due to retardation of $CH_4$ diffusion through soil pores by addition of fine-textured fly ash. In addition, as fly ash has a potential for $CO_2$ removal via carbonation (formation of carbonate precipitates) that decreases $CO_2$ availability that is a substrate for $CO_2$ reduction reaction (one of $CH_4$ generation pathways) is likely to be another mechanisms of $CH_4$ flux reduction by fly ash. Meanwhile, the mean $CO_2$ flux during the entire incubation period was between 0.64 and $0.90g\;CO_2\;m^{-2}day^{-1}$, and that of N treated soil was lower than that without N addition. Because N addition is likely to increase soil respiration, it is not straightforward to explain the results. However, it may be possible that our experiment did not account for the substantial amount of $CO_2$ produced by heterotrophs that were activated by N addition in earlier period than the measurement was initiated. Fly ash application also lowered $CO_2$ flux by up to 20% in the soil mixed with fly ash at 10% through $CO_2$ removal by the carbonation. At the whole picture, fly ash application at 10% decreased global warming potential of emitted $CH_4$ and $CO_2$ by about 20%. Therefore, our results suggest that fly ash application can be a soil management practice to reduce green house gas emission from paddy soils. Further studies under field conditions with rice cultivation are necessary to verify our findings.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.3
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• pp.195-207
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• 2000

Organic and inorganic characteristics including bacterial cell number, enzyme activity, nutrients, and heavy metals have been monitored in twelve acrylic experimental tanks for two weeks to estimate and compare self-purification capacities in two Korean wet-land environments, tidal flat and rice field, which are possibly different with the environments in other countries because of their own climatic conditions. FW tanks, filled with rice field soils and fresh water, consist of FW1&2 (with paddy), FW3&4 (without paddy), and FW5&6 (newly reclaimed, without paddy). SW tanks, filled with tidal flat sediments and salt water, are SW1&2 (with anoxic silty mud), SW3&4 (anoxic mud), and SW5&6 (suboxic mud). Contaminated solution, which is formulated with the salts of Cu, Cd, As, Cr, Pb, Hg, and glucose+glutamic acid, was spiked into the supernatent waters in the tanks. Nitrate concentrations in supernatent waters as well as bacterial cell numbers and enzyme activities of soils in the FW tanks (except FW5&6) are clearly higher than those in the SW tanks. Phosphate concentrations in the SW1 tank increase highly with time compared to those in the other SW tanks. Removal rates of Cu, Cd, and As in supematent waters of the FW5&6 tanks are most slow in the FW tanks, while the rates in SW1&2 are most fast in the SW tanks. The rate for Pb in the SW1&2 tanks is most fast in the SW tanks, and the rate for Hg in the FW5&6 tanks is most slow in the FW tanks. Cr concentrations decrease generally with time in the FW tanks. In the SW tanks, however, the Cr concentrations decrease rapidly at first, then increase, and then remain nearly constant. These results imply that labile organic materials are depleted in the FW5&6 tanks compared to the FW1&2 and FW3&4 tanks. Removal of Cu, Cd, As from the supernatent waters as well as slow removal rates of the elements (including Hg) are likely due to the combining of the elements with organic ligands on the suspended particles and subsequent removal to the bottom sediments. Fast removal rates of the metal ions (Cu, Cd, As) and rapid increase of phosphate concentrations in the SW1&2 tanks are possibly due to the relatively porous anoxic sediments in the SW1&2 tanks compared to those in the SW3&4 tanks, efficient supply of phosphate and hydrogen sulfide ions in pore wates to the upper water body, complexing of the metal ions with the sulfide ions, and subsequent removal to the bottom sediments. Organic materials on the particles and sulfide ions from the pore waters are the major factors constraining the behaviors of organic/inorganic elements in the supernatent waters of the experimental tanks. This study needs more consideration on more diverse organic and inorganic elements and experimental conditions such as tidal action, temperature variation, activities of benthic animals, etc.

• Journal of Wetlands Research
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• v.17 no.3
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• pp.283-292
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• 2015

The total global emission of $CO_2$ from soils is recognized as one of the largest fluxes in the global carbon cycle. Especially it is necessary to quantify the amount of $CO_2$ emitted by the organic material decomposition processes of microorganisms in the soil, because it becomes one of a factor for determining the carbon stocks in the soil. This study was conducted to estimate the impact of the Korean water deer(Hydropotes inermis)' feces to the soil organic matter. Also, effects of Korean water deer' feces on $CO_2$ emissions of soil and land use pattern dependent $CO_2$ flux quantification are studied. The organic materials in the Korean water deer' feces significantly changed organic matter content of soil and influenced the activity of soil microorganisms, both changing of respiration of the soil and physical chemical components in soil. In particular, C/N ratio and the $CO_2$ flux of soil of four regions (Rice paddy, Fallow ground, Salix koreensis community, Phragmites australis community) showed a statistically highly significant correlation (P<0.01) with the presence or absence of feces. $CO_2$ flux of soil affected by the feces was 2-20 times higher than the soil unaffected by the feces. This study has great significance to quantify the extent of the material circulation and its impact to the terrestrial ecosystem and soil zone throughout Korean water deer' feces. Feces of wildlife can affect soil and soil material circulation.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.2
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• pp.53-58
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• 2006

The Korean Ministry of Agricultural & Forestry(MAF) has designated some model areas and has supported financially to encourage sustainable farming under the environment-friendly agriculture rearing project(EARP) since 1995. This study was conducted to diagnose the project and to find ways to improve the effectiveness of EARP. The 18 areas (823 ha) such as Gyeonggi-Do, Gangwon-Do, Chungcheongbuk-Do, Chungcheongnam-Do, and Jeju-Do of 32 areas under EARP in 2004 were examined. Most of the practices implemented in EARP areas were not practical for sustainable agriculture except some equipments and facilities. It was thought that practical technologies for sustainable agriculture were more essential than equipments and facilities to improve the effectiveness of EARP. And area-specific technologies are needed to decrease environmental pollution. For example, liquefied slurry application and duck-rice farming in paddy fields near a watershed could increase the possibility of water pollution by nutrient outflow. Soil characteristics were important factors that could affect the effect of practices on environment conservation. Woodchip application and subsoil crash were not effective in coarse-textured soils. It was recommended that every practices under EARP should be re-examined in the light of the effects on environment before implementation and be evaluated by experts after completion.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.4
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• pp.327-332
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• 1987

Soil samples were collected from the paddy soils growing two crops of rice and garlic in Kyung-pook province. To obtain the basic information on the application of S-fertilizer in the garlic field, the adsorption and release amount of $SO_4{^{-2}}$ in subsoil samples were determined. The ranges of $SO_4{^{-2}}$ contents in surface and sub-soil were 59-117 and 34-102 ppm, respectively. The amount of $SO_4{^{-2}}$ adsorbed by soil samples was found to be more at lower pH and higher concentration of $SO_4{^{-2}}$. The $SO_4{^{-2}}$ adsorption constants in Freundlich equation tended to be higher at lower pH. It is apparent that most of $SO_4{^{-2}}$ was released in the first extraction. However, the lower the pH of extracted solution, the more the $SO_4{^{-2}}$ contents was released by distilled water.

• Journal of Food Hygiene and Safety
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• v.31 no.4
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• pp.227-249
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• 2016

Arsenic and its compounds vary in their toxicity according to the chemical forms. Inorganic arsenic is more toxic and known as carcinogen. The provisional tolerable weekly intake (PTWI) of $15{\mu}g/kg$ b.w./week established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) has been withdrawn, while the EFSA panel suggested $BMDL_{0.1}$ $0.3{\sim}8{\mu}g/kg\;b.w./day$ for cancers of the lung, skin and bladder, as well as skin lesions. Rice, seaweed and beverages are known as food being rich in inorganic arsenic. As(III) is the major form of inorganic arsenic in rice and anaerobic paddy soils, while most of inorganic arsenic in seaweed is present as As(V). The inorganic arsenic in food was extracted with solvent such as distilled water, methanol, nitric acid and so on in heat-assisted condition or at room temperature. Arsenic speciation analysis was based on ion-exchange chromatography and high-performance liquid chromatography equipped with atomic absorption spectrometry and inductively coupled plasma mass spectrometry. However, there has been no harmonized and standardized method for inorganic arsenic analysis internationally. The inorganic arsenic exposure from food has been estimated to range of $0.13{\sim}0.7{\mu}g/kg$ bw/day for European, American and Australian, and $0.22{\sim}5{\mu}g/kg$ bw/day for Asian. The maximum level (ML) for inorganic arsenic in food has established by EU, China, Australia and New Zealand, but are under review in Korea. Until now, several studies have conducted for reduction of inorganic arsenic in food. Inorganic arsenic levels in rice and seaweed were reduced by more polishing and washing, boiling and washing, respectively. Further research for international harmonization of analytical method, monitoring and risk assessment will be needed to strengthen safety management of inorganic arsenic of foods in Korea.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.1
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• pp.78-88
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• 1985

Nitrogen fertilizer effectiveness on rice production was studied to evaluate the different forms and sources. Seven kind of nitrogen fertilizers were applied in two levels, 15 and 30 kg per 10a on Jinjubyeo (Japonica type) in silt loam paddy soil of pot cultivation. The results were summerized as follows; 1. pH in soils was decreased with enhancement of ammonium sulfate application in $NH_4-N$, but it was increased with times after nitric-acid application and PH change in soil was not remarkable when $NO_3-N$ with accessory component was applied. 2. $NH_4-N$ contents in soil were the lowest at 2 weeks after application in N 15kg/10a regardless of different sources of nitrogen fertilizer. $NO_3-N$, in N 30kg/10a, was decreased continuously until 4 weeks, while $NH_4-N$, Urea-N were at minimum during 2-3 weeks. 3. Growth of culm length and straw weight applied with AN (Ammonium Nitrate), AS (Ammonium Sulfate) and urea were superior to the form of nitrate. While NA (Nitric Acid), PN (Potassium Nitrate) and CN (Calcium Nitrate) plot of the $NO_3-N$ was the dominant fertilizers for root elongation. 4. Brown rice yields were increased dominantly by $NH_4-N$ application such as AS or AP than $NO_3-N$ pot. But the yields in case of $NO_3-N$ application CN, PN and NA were decreased. 5. N, P, Mg and Mn content of straw ranked the effectiveness of nitrogen forms as $NH_4-N$, Urea-N and $NH_4-N+NO_3-N$, while K, Ca and $SiO_2$ content of straw in $NO_3-N$ fertilizer plot were high while N, P, Mg, Mn, Fe and Mg were low. 6. Increament of nitrogen absorption in straw was stimulated by enhancement of phosphorous absorption and the growth and yield of rice plant were increased. Absorption of N, P, Ca and Mg was decreased by CN application. Absorption of N, P and Mg also was decreased by $NO_3-N$ application and N, P, Mg or Ca content were seemed to simulated the growth and yield of rice plant. 7. $SiO_2$, Zn and Fe contents of the root at harvest stage were higher than those of the straw. N, P, Mg, Mn, Zn and Fe contents were high in $NH_4-N$ and Urea treatment. While K, ca and $SiO_2$ contents, however, were high in $NO_3-N$ treatment.

• Applied Biological Chemistry
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• v.20 no.1
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• pp.58-65
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• 1977

A laboratory experiment was carried out with loamy paddy soily under Hooded condition to study the effects of some pesticides on the decomposition rate of urea and the transformation of nitrogen. The pesticides used in this study are ten kinds, which are usually applicable for rice cropping. The soil was treated with 200ppm of fertilizer urea-N and different levels of pesticides and then incubated at $28{\pm}1^{\circ}C$ for two weeks. The kinds of pesticides used in this study were three kinds of herbicides (2,4-D, Machete and TOK), three kinds of fungicides (Rabcide, Neo-asozine and Phenazine) at the levels of 20,100 and 200ppm and four kinds of insecticides (Birlane, Diazinon, Sumithion and Bux) at the levels of 50,250 and 500ppm. respectively. The results obtained may be summarized as follows. 1. The treatments of herbicides and fungicides show little effect on the decomposition rate of urea at the levels of 20 and 100ppm, but by the treatment of 200ppm it was retarded markedly after one day incubation aside from Rabcide and Neo-asozine. The decomposing rate of urea was inhibited weakly by the treatment with 250ppm of Sumithion and Bux, however, 500ppm of all kinds of insecticides treated in this study brought about strong inhibitory effect (over 50%) after only one day incubation. The applied urea was disappeared nearly completely in three days in all cases with and without pesticides. 2. The production of ammonium-N was increased with the increase of pesticide concentrations gradually through two weeks and otherwise in the control sample a loss of inorganic-N resulted in about 20% extent. 3. The inhibitory effect of the all applied pesticides on_the_ nitrification under flooded condition was observed markedly and may be ordered as insecticides, herbicides and fungicides according to its inhibiting action.