• Journal of Applied Biological Chemistry
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• 제48권4호
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• pp.187-192
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• 2005

Influence of herbicide oxadiazon on soil microbial activity and nitrogen dynamics was evaluated. Soil samples were treated with oxadiazon at field and tenfold field rates and incubated. Organic amendment was added as an additional substrate for soil microorganisms. Tenfold field rate oxadiazon stimulated substrate-induced respiration (SIR) and dehydrogenase activity (DHA) in amended soil as compared to unamended soil and control treatment. Soil urease activity was not affected by oxadiazon treatment. In both amended and unamended soils, treatment of the herbicide at higher rate had not significant influence on $NH_4$-N and $NO_3$-N concentrations. Higher dose of oxadiazon was degraded in both soils, but dissipation rate in amended soil was higher than unamended soil, with half-lives ($t_{1/2}$) of 23.1 and 138.6 days, respectively. Recommended field rate did not affect microbial activity and nitrogen dynamics in soil ecosystem. Results showed influence of oxadiazon on cycling processes of nitrogen in soil was not significant however its effect on microbial activity was a tendency depending on addition of organic amendment to soil.

• 한국유기농업학회지
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• 제25권4호
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• pp.805-819
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• 2017

The study was carried out to develop a mathematical model for evaluating the effect of organic fertilizers in organic rice production systems. A function to simulate the nitrogen mineralization process in the paddy soil has been developed and integrated into ORYZA2000 crop growth model. Inorganic nitrogen in the soil was estimated by single exponential models, given temperature and C:N ratio of organic amendments. Data collected from the two-year field experiment were used to evaluate the performance of the model. The revised version of ORYZA2000 provided reasonable estimates of key variables for nitrogen dynamics and crop growth in the organic rice production systems. Coefficient of determination between the measured value and simulated value were 0.6613, 0.8938, and 0.8092, respectively for soil inorganic nitrogen, total dry matter production, and rice yield. This means that the model could be used to quantify nitrogen supplying capacity of organic fertilizers relative to chemical fertilizer. Nitrogen dynamics and rice growth simulated by the model would be useful information to make decision for organic fertilization in organic rice production systems.

• Journal of the korean society of oceanography
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• 제39권4호
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• pp.222-233
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• 2004

Using nitrogen as the limiting nutrient, the default version of a microplankton-detritus model linked chlorophyll concentration to the autotroph nitrogen. However, phosphorus dynamics were added to simulate the results of a microcosm experiment. Using standard parameter values with a single value of microheterotroph fraction in the microplankton taken from the observed range, the best simulation successfully captured the main features of the time-courses of chlorophyll and particulate organic carbon, nitrogen and phosphorus, with root-mean-square error equivalent to 29% of particulate concentration. A standard version of microbiological model assumes complete internal cycling of nutrient elements; adding a term for ammonium and phosphate excretion by microheterotrophs did not significantly improve predictions. Relaxing the requirement for constant microheterotroph fraction resulted in an autotroph-heterotroph model AH, with dynamics resembling those of a Lotka-Volterra predator-prey system. AH fitted the microcosm data worse than did MP, justifying the suppression of Lotka-Volterra dynamics in MP. The paper concludes with a discussion of possible reasons for the success of the simple bulk dynamics of MP in simulating microplankton behaviour.

• 환경생물
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• 제24권2호
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• pp.186-194
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• 2006

Nitrogen dynamics of Seagrass Zostera marina were investigated in both Dongdae Bay and Ojiri from March to August, 2004. All seagrass samples were separated into four fractions such as leaves (new and adult), sheath and rhizome in order to understand temporal variations of nitrogen content in different fractions of Zostera marina. There are temporal variations of shoot production rates and total nitrogen contents in their different fractions at both study areas. Leaf production were almost 4 to 5 fold higher in summer than in winter. The irradiance is the primary factor controlling the leaf production of Zostera marina in both sites although water temperature also influence its productivity. Nitrogen contents of leaves were overall low in summer than in winter, but nitrogen content of rhizome increased during the summer season. In addition, nitrogen contents of new leaves were mostly higher than adult leaves in spite of lower nitrogen content of new and adult leaves in high productivity period. This result suggests that Zostera marina seems to have significant translocation ability of nitrogen in a shoot. The nitrogen content of leaf tissue may reflect nutritional nitrogen availability.

• 한국유기농업학회지
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• 제8권2호
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• pp.97-110
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• 2000

An organic agriculture should be managed by mixed farming in farm unit as a closed recycling system. Due to restricted purchased of fertilizers from outside, organic farmer has to deal with limited amount of nutrient source in farm unit. Especially the supply of the essential nutrient, nitrogen, mostly depends on legumes fixing nitrogen optimizing the site-adapted crop rotation. Dynamics of humus and metabolic plant carbon and active soil carbon compartment in active and passive humuspool by rotation system was explained, and dynamics of potentially mineralizable nitrogen in organic nitrogen and biomass was discussed. It was also discussed comparison of ammonia emission, potential greenhouse effect, primary energy input, acidification potential, CO2 emission between organic and conventional farming, the nitrate-nitrogen dynamic in the soil profile by organic, integrated and conventional farming system. In conclusion, it was suggested for Korean Organic Agriculture that the importance of legumes and green manures in rotation system for increase/maintenance of soil ferfility, and was pointed out the need of investment for environment impact of Korean organic farming implement.

• Journal of Microbiology and Biotechnology
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• 제26권5호
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• pp.900-908
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• 2016

The effects of algal inoculation on chemical oxygen demand (COD) and total nitrogen (TN) removal, and indigenous bacterial dynamics were investigated in municipal wastewater. Experiments were conducted with municipal wastewater inoculated with either Chlorella vulgaris AG10032, Selenastrum gracile UTEX 325, or Scenedesmus quadricauda AG 10308. C. vulgaris and S. gracile as fast growing algae in municipal wastewater, performed high COD and TN removal in contrast to Sc. quadricauda. The indigenous bacterial dynamics revealed by 16S rRNA gene amplification showed different bacterial shifts in response to different algal inoculations. The dominant bacterial genera of either algal case were characterized as heterotrophic nitrifying bacteria. Our results suggest that selection of indigenous bacteria that symbiotically interact with algal species is important for better performance of wastewater treatment.

• 한국작물학회:학술대회논문집
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• 한국작물학회 1999년도 춘계 학술대회지
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• pp.82-83
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• 1999

• Journal of Ecology and Environment
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• 제30권3호
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• pp.209-223
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• 2007

Twenty-four wetlands located in Higashi-Hiroshima City in West Japan were selected for this study in order to investigate both the relationship between aquatic plant composition and environmental conditions; and the relationship between changing land use patterns in the catchments and the concentration of different forms of nitrogen in the wetlands. The dominant and subdominant species which comprised the principal vegetation were determined based on a vegetation census conducted in each wetland during the growing season from June to August, 2006. The seasonal variations of water quality factors (pH, electrical conductivity, turbidity, dissolved oxygen, total dissolved solid, and temperature) and different forms of nitrogen such as nitrite, nitrate, ammonium, total nitrogen, dissolved organic nitrogen and dissolved inorganic nitrogen concentrations were analyzed as important indicators of water quality for the surface water of the wetlands. The surveyed wetlands were classified into three types (non-disturbed wetlands, moderately-disturbed wetlands and highly-disturbed wetlands), based on the degree of human disturbance to their catchment areas. An analysis of variance indicated that there was a significant difference among the wetland groups in the annual mean values of electrical conductivity, total dissolved solids, total nitrogen, nitrite, dissolved inorganic nitrogen and dissolved organic nitrogen. Classification of the wetlands into three groups has revealed a pattern of changes in the composition of plant species in the wetlands and a pattern of changes in nitrogen concentrations. A majority of the non-disturbed wetlands were characterized by Brasenia schrebi and Trapa bispinosa as dominant; with Potamogeton fryeri and Iris pesudacorus as sub-dominant species. For most of the moderately-disturbed wetlands, Brasenia schrebi were shown to be a dominant species; Elocheriss kuriguwai and Phragmites australis were observed as sub-dominant species. For a majority of the highly-disturbed wetlands, Typha latifolia and T. angustifolia were observed as dominant species, and Nymphea tetragona as the sub-dominant species in the study area. An analysis of land use and water quality factors indicated that forest area played a considerable role in reducing the concentration of nutrients, and can act as a sink for surface/subsurface nutrient inputs flowing into wetland water, anchor the soil, and lower erosion rates into wetlands.

• 한국수산과학회지
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• 제37권1호
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• pp.24-32
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• 2004

A mathematical model is used to investigate nitrogen dynamics in the intensive aquaculture ponds in the western coast of Korea. Parameters associated with water quality, sediments and growing of shrimp (Fenneropenaeus chinensis) are measured to calibrate the model for feeding ponds A and B and storage ponds. The model describes the fate of nitrogen including loadings of ammonia from feeds, phytoplankton assimilation, nitrification, sedimentation, volatilization and discharge. The model obtains good agreements with the measured values of TAN $(NH_4,\;NH_3),\;NO(NO_2,\;NO_3)$ and Chl (chlorophyll a). Impacts of water exchange on TAN and Chl are investigated, showing that the range of 0.01-0.2 (/day) cannot effectively reduce TAN but reduces Chl. Nitrogen in the ponds A is removed by sedimentation $66\%,$ volatilization $8\%,$ discharge of particulate and dissolved $8\%.$ The pond B shows $56\%\;and\;26\%$ of sedimentation and volatilization, respectively, to yield $10\%.$ decrease and 8c/o increase compared to those in the pond A. While the pond A has larger area (1.02:0.66 ha) and same stocking density (0.025 md./L) at the beginning of culture, the pond B obtains higher stocking density (0.0065:0.0091 md./L), longer feeding period (103:121 day) and resultant higher shrimp production (1.15:2.13 t/ha/cycle) at harvest. This is possibly due to the hydraulic characteristics driven by paddlewheels. At low ratio of the low speed area and the pond area, the rate of sedimentation is high, while the rate of gas exchange is low. Thus, the measurement and model analysis suggest that water quality and shrimp production are positively correlated with the hydraulic characteristics in the shrimp ponds.

• Animal Bioscience
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• 제35권2호
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• pp.260-271
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• 2022

Objective: We aimed to investigate the effect of the differing amino acid (AA) release dynamics of two protein sources on the growth performance, nitrogen deposition, plasma biochemical parameters, and muscle synthesis and degradation of piglets when included in their diets at normal and low concentrations. Methods: Forty-eight piglets (Duroc×Landrace×Large White) with initial body weight of 7.45±0.58 kg were assigned to six groups and fed one of 6 diets. The 6 dietary treatments were arranged by 3×2 factorial with 3 protein sources and 2 dietary protein levels. They are NCAS (a normal protein content with casein), NBlend (a normal protein content with blend of casein and corn gluten meal), NCGM (a normal protein content with corn gluten meal), LCAS (a low protein content with casein), LBlend (a low protein content with blend of casein and corn gluten meal), LCGM (a low protein content with corn gluten meal). The release dynamics of AA in these diets were determined by in vitro digestion. The digestibility, utilization and biological value of nitrogen in piglets were determined by micro Kjeldahl method. Plasma insulin was measured by enzyme-linked immunosorbent assay kits. The protein expression of mediators of muscle synthesis and degradation was determined by western blotting. Results: Although the consumption of a low-protein diet supplemented with crystalline AA was associated with greater nitrogen digestion and utilization (p<0.05), the final body weight, growth performance, nitrogen deposition, and phosphorylation of ribosomal protein S6 kinase 1 and eIF4E binding protein 1 in the muscle of pigs in the low-protein diet-fed groups were lower than those of the normal-protein diet-fed groups (p<0.05) because of the absence of non-essential AA. Because of the more balanced release of AA, the casein (CAS) and Blend-fed groups showed superior growth performance, final body weight and nitrogen deposition, and lower expression of muscle ring finger 1 and muscle atrophy F-box than the CGM-fed groups (p<0.05). Conclusion: We conclude that the balanced release of AA from CAS containing diets and mixed diets could reduce muscle degradation, favor nitrogen retention, % intake and improve growth performance in pigs consuming either a normal- or low-protein diet.