• Korean Journal of Soil Science and Fertilizer
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• v.23 no.3
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• pp.227-231
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• 1990

A pot experiment was conducted to find out the effect of zeolite application on the growth and $N^2$ fixation of pea plants. The results are as follows. 1) The dry weight of pea plants grown with N-fertilizer application was smaller than that without N, but In was increased by application of zeolite 2) The N content in pea plants was increased by zeolite application. The N increment was smaller in 2% zeolite plots than in 1% zeolite plots. Larger amount of Ammonium were remained in the former plots. 3) The N amounts accumulated in different parts of plant derived from $^{15}N$-labelled fertilizer were decreased by application of zeolite. 4) The N derived from atmuspheric $N_2$ was increased by zeolite application. However, the application of fertilizer nitrogen depressed the enhancement of fixed-N accumulation.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.3
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• pp.381-396
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• 2004

In order to understand the precipitation acidity and chemical composition of ion species in Iksan area as well as to know the difference of chemical characteristics in precipitation samples from the viewpoint of precipitation sampling method, precipitation samples were collected by wet-only automatic precipitation sampler and bulk manual precipitation sampler in Iksan, from March 2003 to August 2003. The mean pH of precipitation was 5.0. There was a little significant difference in the mean value of pH between automatic and manual sampler. However, pH values of some precipitation samples were lower in automatic sampler than in manual sampler, especially in case of precipitation samples with small rainfall for March 2003. The mean concentrations of each ions in precipitation were generally a little higher in precipitation samples collected by the manual sampler than in those collected by the automatic sampler because of accumulation of dry deposition on the surface of glass funnel installed at the manual sampler during the sampling period or no rainfall. Dominant species determining the acidity of precipitation, were N $H_4$$^{[-10]}$ and nss-C $a^{2+}$ for cations and nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ for anions. The mean concentration of N $H_4$$^{+}$ and nss-C $a^{2+}$ were 31 $\mu$eq/L and 9 $\mu$eq/L for the automatic sampler and 40 ueq/L and 16 ueq/L for the manual sampler, respectively. In addition, nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were 27 $\mu$eq/L and 13 $\mu$eq/L for the automatic sampler and 32 $\mu$eq/L and 17 $\mu$eq/L for the manual sampler, respectively. Although the concentrations of the acidifying ions of nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were about 3 times higher than those for foreign pristine sites, precipitation acidity were estimated to be natural due to the neutralization reaction of the alkaline species of N $H_4$$^{+}$ and nss-C $a^{2+}$ with its higher concentrations. Considering the ratios of nss-S $O_4$$^{2-}$/N $O_4$$^{[-10]}$ nss-S $O_4$$^{2-}$, it was found that ammonium sulphate was dominant in Iksan precipitation. The major non-sea salt ions were maximum concentrations for March, but decreased with increasing of precipitation amount.on amount.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.3
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• pp.164-169
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• 2008

This experiment was carried out to find the growth response and changes of nitrate and soluble sugar content in tomato leaves with salt stress. Tomato (Solanum lycopericum) seedlings were grown under different electrical conductivity (EC) levels adjusted with $CaCl_2$ as 1, 2, and $6dS\;m^{-1}$. The growth response and contents of nitrate and soluble sugar in tomato plants were examined at 7 and 14 days after salt treatment. Leaf area and dry weight ratio of shoot to root of tomato plants were decreased as EC level increased. Photosynthetic rate of leaves was reduced under high EC level due to the stomatal closure and the reduction of transpiration rate. The soluble sugar and starch content were lower in the tomato leaves grown under high EC level. Total nitrogen and nitrate contents were decreased in high EC level, whereas the ammonium content was increased. High-salt stress induced the accumulation of salt crystal in mesophyll cells of tomato leaf.

• Environmental Engineering Research
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• v.13 no.3
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• pp.125-130
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• 2008

Free ammonia ($NH_3$-N) inhibition of nitrite-oxidizing bacteria (NOB) has been widely studied for partial nitrification (or nitrite accumulation) and denitrification via nitrite ($NO_2^-$-N) as a low-cost treatment of ammonium containing wastewater. The literature on $NH_3$-N inhibition of NOB, however, shows disagreement about the threshold $NH_3$-N concentration and its degree of inhibition. In order to clarify the confusion, a simple and cheap respirometric method was devised to investigate the effect of free ammonia inhibition of NOB. Sludge samples from an autotrophic nitrifying reactor were exposed to various $NH_3$-N concentrations to measure the maximum specific nitrite oxidation rate ($\hat{K}_{NO}$) using a respirometer. NOB biomass was estimated from the yield values in the literature. Free ammonia inhibition of nitrite oxidizing bacteria was reversible and the specific nitrite oxidation rate ($K_{NO}$) decreased from 0.141 to 0.116, 0.100, 0.097 and 0.081 mg $NO_2^-$-N/mg NOB h, respectively, as the $NH_3$-N concentration increased from 0.0 to 1.0, 4.1, 9.7 and 22.9 mg/L. A nonlinear regression based on the noncompetitive inhibition mode gave an estimate of the Inhibition concentration ($K_I$) of free ammonia to be 21.3 mg $NH_3$-N/L. Previous studies gave $\hat{K}_{NO}$ of Nitrobacter and Nitrospira as 0.120 and 0.032 mg/mg VSS h. The free ammonia concentration which inhibits Nitrobacter was $30{\sim}50\;mg$ $NH_3$-N/L and Nitrospira was inhibited at $0.04{\sim}0.08\;mg$ $NH_3$-N/L. The results support the fact that Nitrobacter is the dominant NOB in the reactor. The variations in the reported values of free ammonia inhibition may be due to the different species of nitrite oxidizers present in the reactors. The respirometric method provides rapid and reliable analysis of the behavior and community of the nitrite oxidizing bacteria.

• Applied Biological Chemistry
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• v.43 no.3
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• pp.163-168
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• 2000

To remove phosphate accumulated in the soil and water, Acinetobacter lwoffi PO8 possessing a high ability to accumulate phosphate was isolated from a active sludge. Bacterium was cultured in the liquid medium containing $150\;{\mu}g/mL$ of phosphate at $30^{\circ}C$ in different culture conditions to examine intracellular phosphate uptake. The initial pH in the range of $7.5{\sim}8.5$ was effective on the growth and phosphate uptake of the strain. Glycerol and arabinose used as a carbon sources showed 93 and 91% the phsphate uptake, respectively. Among the nitrogen sources, ammonium salt such as $NH_4NO_3$ and $(NH_4)_2SO_4$ was effectively utilized on the phosphate uptake compared with amino compounds. The rate of phosphate uptake of $NH_4NO_3$, and $(NH_4)_2SO_4$, was 95 and 96%, respectively The growth and Phosphate uptake ability in the strain were significantly promoted when metal ions were added in the medium; $Co^{2+}$, however, was not utilized by the strain. The capacity of phosphate uptake was enhanced to $10{\sim}20%$ when arginine, methionine, or lysine was added. Using $^{32}P$ to examine the uptake Pattern of intracellular phosphate, experiment result showed that polyphosphate was largely found in the fraction of intracellular inorganic phosphate of Acinetobacter lwoffi PO8.

• The Korean Journal of Zoology
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• v.39 no.1
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• pp.36-46
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• 1996

An endogenous phenoloxidase (EPO) from earthworm, Lumbricus rubellus, has been purified and characterized. The purified EPO using ammonium sulfate fractionation, Blue-2, Phenyl-, and Q-sepharose chromatography steps was revealed in SDS-PAGE as a single protein banri with Mr. of 59 kl)a. A native strudure of the enzyme was examined with an in situ staining of a nondenatudng-PAGE using DL-dopa as a substrate. The result showed that a single band due to the EPO activity was located siighdy above a standard polypeptide with Mr. of 210 kl)a. These fads indicate that the EPO is an oligomeric enzyme. The presence of a monophenolase activity of the purified EPO, which hydroxylates tyrosine to dopa, was confirmed by observing dopachrome accumulation at 475 nm at PH 8.0 with a typical lag phase during 60 mm. of meausrement. A series of inhibition study has been performed for the enzyme with several divalent cation chelators such as phenyithiourea (Flu), 1, lO-phenanthroline, EDTA, and EGTA. Among them, only V'flj inhibited the enzyme with 1C0.5 of 65 MM, which indicated that copper was critical for the catalysis of EPO. The enzyme was maximally active at 35'C and pH 8.0 when L-dopa to dopachrome conversion was spectrophotometricaily monitored at 475 nm. The apparent Km values of P0 for L-opa were obtained as 1.86 mM and 13.8 mM at pH 6.5 and 8.0, respectively. The catalytic efficiencies at both pH were almost identical [(kat/Km)pH8.0/(kcat/Km)pH6.5 = O.92] while the Vmax at p11 8.0 was 6.6-fold higher than that at pH 6.5. This fact may indicate that pH affeds the catalysis at substrate and/or enzyme-substrate complex level rather than the enzyme itself. Taken together, the EPO was an oligomeric enzyme which did not require proteolysis for its activation. These results also indicated that the enzyme can exist, at least, in part as a latent form In vivo, which might be distinct from the prophenoloxidase activating system. Therefore, it is pertinent to consider that there must be certain regulatory molecules or phenomena in L. rubellus which make the 1,0 in a latent form in vivo before the foreign invasions.

• Journal of Bio-Environment Control
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• v.32 no.2
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• pp.97-105
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• 2023

Concentration of nitrogen, one of the major elements, and ratio of two nitrogen forms (NH₄⁺ and NO₃^-) in the nutrient solution affect the quality and food safety of fresh vegetable produce. This study was conducted to find an appropriate strength and NH₄⁺:NO₃^- ratio of a nutrient solution for growth and development of a Romaine lettuce (Lactuca sativa L. var. longiflora) 'Caesar Green', a representative leafy vegetable, grown in a home hydroponic system. In the first experiment, plants were grown using three types of nutrient solution: A commercial nutrient solution (Peters) and two strengths (GNU1 and GNU2) of a multipurpose nutrient solution (GNU solution) developed in a Gyeongsang National University lab. Plants grown with the GNU1 and GNU2 had greater shoot length, leaf length and width, and biomass yield than Peters. On the other hand, the root hairs of plants grown with Peters were short and dark in color. Tissue NH₄⁺ content in the Peters was higher than that of the GNU1 and GNU2. The higher contents of NH₄⁺ in this solution may have caused ammonium toxicity. In the second experiment, eight treatment solutions, combining GNU1 and GNU2 solutions with four ratios of NO₃^- :NH₄⁺ named as 1, 2, 3 and 4 were used. Both experiments showed more growth in the GNU2 group, which had a relatively low ionic strength of the nutrient solution. The growth of Romaine lettuce showed the greatest fresh weight along with low tissue NO₃^- content in the GNU2-2. This was more advantageous in terms of food safety in that it suppressed the accumulation of surplus NO₃^- in tissues due to the low ionic trength of the GNU2 subgroup. In addition, this is preferable in that it can reduce the absolute amount of the input of inorganic nutrients to the nutrient solution.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.4
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• pp.392-399
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• 1998

Nitrogen fertilizers such as urea are readily hydrolyzed in soils to produce ammonium ions which pass through nitrification and denitrification processes. These serial processes have drawn attention due to nitrogen losses, eutrophication, blue baby syndrome, and ozone depletion problems. The purpose of this study was to test the inhibitory effects of hot-water extract and organic solvent fractions of Artemisia asiatica leaves on soil urea hydrolysis and nitrification. In addition, the effects of organic solvent fractions on urease activity and ureolytic bacterial population were also investigated. First, hot-water extract of Artemisia asiatica leaves inhibited soil nitrification substantially with a marginal stimulatory effect on soil urea hydrolysis. Soils treated with hot-water extract of Artemisia asiatica leaves showed significant decreases in the accumulation of soil $NO_3-N$ (~68% decrease) compared with the control soil without the treatment of hot-water extract. In contrast, $CHCl_3$/MeOH fraction and basic aqueous layer of Artemisia asiatica leaves inhibited soil urea hydrolysis very strongly, causing 5.8 and 4.3-fold higher accumulation in amounts of remaining urea-N compared with the non-treated soil. Meanwhile, non of the organic solvent fractions showed any significant effects on soil nitrification inhibition. The inhibition of ureolytic bacterial activity by $CHCl_3$/MeOH fraction and aqueous basic layer of Artemisia asiatica leaves without any effects on urease activity itself led us to conclude that the inhibitions of soil urea hydrolysis were caused by the antagonistic effects on ureolytic bacterial activity.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.393-401
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• 2017

The nitrate ($NO_3{^-}$) accumulation of hydroponically grown leafy vegetables may increase in the condition of a closed-type plant production system with low light intensity due to low activity of enzymes involved in nitrogen assimilation and the use of $NO_3-N$ as major nitrogen source. The objective of this study is to investigate the effects of light intensities, nutrient solution compositions and the time of nutrient solution removal before harvest on nitrate contents of hydroponically-grown lettuces in a closed plant production system. The reduction of nitrate contents in leafy lettuces 'Cheongchima' was higher in the treatments of 'TW' (nutrient solution removal) and '$(NH_4)_2CO_3$' (use of ammonium carbonate as nitrogen source) than those in other treatments, which significantly lowered fresh weight and leaf area of the plants. In the light intensity of $100{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, the nitrate content was effectively reduced without causing any growth retardation, by substitution of the nutrient solution composition that $NO_3-N$ was removed ('$NO_3-N$ removal' treatment) or the half strength of standard nutrient solution was applied ('1/2 S' treatment), for 7days before harvest. The effects of light intensity and the time of nutrient solution removal before harvest on growth and nitrate contents in leafy lettuces were investigated. The nitrate contents in leaves under the light condition of $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ before nutrient solution removal were lower than those of 100 or $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. The removal of nutrient solution for 7 days before harvest quickly reduced the amount of nitrates in leaves in all the light intensities with a greater degree under the $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ of light condition, while the 7 days-removal with both 200 and $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ of light conditions caused decrease in 16~31% of leaf area and 20~35% of fresh weight, compared to the 3 days-removal treatment. The nitrate contents were greatly reduced from 3,018 to 1,035 in $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, and 2,021 to 480 ppm in the light condition of $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, with the nutrient solution removal for 3 days before harvest, without causing any deterioration in growth and product quality. The vitamin C contents in leaves were higher in the treatment of nutrient solution removal for both 3 and 5 days before harvest with the light condition of $300{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ than those in the light condition of 100 or $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$.

• Korean Journal of Soil Science and Fertilizer
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• v.9 no.1
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• pp.17-23
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• 1976

In order to investigate the fate of nitrogen in the paddy soil, Suchang, Hwasoon and Susan soil which have different properties, were treated with several nitrogen fertilizers such as ammonium chloride, ammonium sulfate, urea and SCU (sulfur-coated urea), and incubated under water-logged condition in $30^{\circ}C$ incubator. $NH_4-N$, $NO_3-N$, $Fe^{++}$ and pH in soil and stagnant water, were determined at 10, 20, 30, 40 and 50 days after incubation. The obtained results were summarized as follows: 1. The effect of rising temperature was increased in order of Hwasoon>Suchang>Susan and the effect of air drying soil was risen in order of Susan>Hwasoon>Suchang, while the rate of ammonication was in order of Susan>Suchang>Hwasoon. 2. The changes of $NH_4-N$ in stagnant water was dependent upon the nitrogen concentration of $NH_4Cl$ and $(NH_4)SO_4$ plat was high and decreased after 30 days incubation, but increased after 40 days and then decreased again. In contrast with the above, $NH_4-N$ concentration of urea and SCU plot was low but the change showed slightly through the incubation period. 3. Accumulation of $NH_4-N$ in the oxidative layer of the $NH_4Cl$ and $(NH_4)_2SO_4$ plot was higher than that of urea and SCU plot and $NH_4-N$ content was decreased with the incubation period. The change of $NH_4-N$ in the reductive layer showed the same pattern. 4. The changes of $NO_3-N$ in the stagnant water were different according to soil properties and nitrogen fertilizer. $NO_3-N$ concentration in stagnant water of urea and SCU plot was higher than in the $NH_4-Cl$ $(NH_4)_2SO_4$ plot and nearly disappeared after 30 to 40 days incubation. 5. The $NO_3-N$ concentration in the oxidative layer of soil was higher than reductive layer. The pattern of change was different in accordance with soil properties and nitrogen fertilizers. In general, nitrification in urea and SCU plot was more increased than $(NH_4)_2SO_4$ plot. In reductive layer, the concentration of $NO_3-N$ was very low until 30 days incubation and thereafter increased slightly. 6. Upon the concentration of $NH_4-N$ and $NO_3-N$ in stagnant water and soil, it was assumed that denitification of urea and SCU plot was higher than $NH_4Cl$ and $(NH_4)_2SO_4$ plot and denitrified nitrogen in incubation period was above 50%.