• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.36-46
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• 2004

We evaluated the effect of limiting nutrients and N/P ratio on the growth of phytoplankton in a small eutrophic reservoir from November 2002 to December 2003. Nutrient limitation was investigated seasonally using nutrient enrichment bioassay (NEB). DIN/DTP and TN/TP ratio (by weight) of the reservoir during the study period ranged 17${\sim}$187 and 13${\sim}$60, respectively. Most of nitrogen in the reservoir account for $NO_3$-N, but sharp increase of ammonia was evident during the spring season. Seasonal variation of dissolved inorganic phosphorus concentration was relatively small. DTP ranged 26.5${\sim}$10.1 ${\mu}g\;P\;L^{-1}$, and the highest and lowest concentration was observed in August and December, respectively. Chlorophyll a concentration ranged 28.8${\sim}$109.7 ${\mu}g\;L^{-1}$, and its temporal variation was similar to that of cell density of phytoplankton. Dominant phytoplankton species were Bacillariphyceae (Melosira varians) and Chlorophyceae (Dictyosphaerium puchellum) in Spring (March${\sim}$April). Cyanophyceae, such as Osillatoria spp., Microcystis spp., Aphanizomenon sp. dominated from May to the freezing time. TN/TP ratio ranged from 46 to 13 (Avg. 27${\pm}$6) from June to December when cyanobacteria (Microcystis spp.) dominated. p limitation for algal growth measured in all NEB experiments (17cases), while N limitation occurred in 8 out of 17 cases. The growth rates of phytoplankton slightly increased with decreasing of DIN/DTP ratio. Evident increase was observed in the N/P ratio of > 30, and it was sustained with DTP increase until 50 ${\mu}g\;P\;L^{-1}$. Under the same N/P mass ratio with the different N concentrations (0.07, 0.7and 3.5 mg N $L^{-1}$), Microcystis spp. showed the highest growth rate in the N/P ratio of< 1 with nitrogen concentration of 3.5 mg N $L^{-1}$). The responses of phytoplankton growth to phosphate addition were clearly greater with increase of N concentration. These results indicate that the higher nitrogen concentration in the water likely induce the stronger P-limitation on the phytoplankton growth, while nitrogen deficiency is not likely the case of nutrient limitation.

• 한국해양학회지
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• v.23 no.4
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• pp.194-206
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• 1989

Seasonal variations of nutrients (ammonium, nitrite, nitrate, phosphate and silicate), primary productivity and ammonium regeneration rate of macrozooplankton were investigate to understand the relationship between nitrogen recycling and nitrogen requirement by phytoplankton from Feburuary 1986 to November 1987 in the Kyunggi Bay, shallow estuarine water of Yellow Sea. In general, nutrients increased during the winter and depleted during the spring and the early summer except temporally sharp increase after flood in September. Ammonium was prevalently generally found in high concentration throughout the study area and it occasionally raised N/P ratio in the range of 30 to 70 as in the freshwater environment. Daily net primary productivity ranged from 30.3 to 3580.0 mgC/$m^2$/d with an average of 883.9 mgC/$m^2$/d. Annual primary productivity was determined to be 320.0 gC/$m^2$/yr. Carbon assimilation number ranged from 2.9 to 19.4 mgC/mg chl-a/h which increased in the summer and decreased in the winter. Nitrogen requirement by phytoplankton ranged from 0.4 to 45.0 mg at-N/$m^2$/d and turnover time of inorganic nitrogen ranged from 2.4 in the late summer to 122.7 days in the winter. Nitrogen regeneration rate of mixed macrozooplankton determined by bottle incubation method ranged from 0.02 to 1.34 mg at-N $m^2$/d and it could contribute from 2.8 to 38.7% with an annual average of 14.9% of total nitrogen requirement by phytoplankton in this shallow estuarine environment.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.285-293
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• 2007

The study was to determine zonal characteristics of nutrients and chlorophyll and evaluate their trophic relations in Daechung Reservoir. For this study, we compared longterm water quality data among three zones along with trophic state using 1993 to 2002 dataset, obtained from the Ministry of Environment, Korea. Total phosphorous (TP), Secchi depth (SD) and chlorophyll (CHL) showed typical longitudinal declines from the riverine to lacustrine zone, but total nitrogen (TN) was not evident. Largest seasonal variations in TP and CHL occurred during the summer monsoon from July to August. In the reservoir, ambient TN averaged 1.67 mg $L^{-1}$ and ratios of TN : TP averaged 88.04, indicating that nitrogen is not likely limited but phosphorus limitation was evident. Trophic State Index (TSI), based on CHL, TP, and SD, varied depending on the zones and seasons. Mean TSI (TP) in the riverine zone was 62 during the monsoon, indicating a hypertrophic condition, whereas the mean was 40 in the lacustrine, indicating a nearly oligotrophic. Values of TSI (CHL) showed maximum in the transition zone during the monsoon. The deviation analysis of TSI showed that about 65% of TSI (CHL)-TSI (TP) and TSI (CHL)-TSI (SD) values were less than zero and the lowest values were -42, indicating an effect of inorganic turbidity on algal growth in the reservoir. Correlation analysis of CHL vs. SD shewed greater correlation coefficient (p<0.001, r=-0.47) in the transition than other two zones (p<0.001, $r{\leq}-0.40$). Correlation analysis of TP vs. CHL was greatest in the lacustrine and TP was minimum in the lacustrine zone, indicating a lowest yield of algal biomass in the lacustrine. Overall data suggests that zonal response of chlorophyll yield at a given nutrient unit is clearly differed among the longitudinal gradients, so the management strategy such as cross sectional modelling should be provided in each zone.

• Korean Journal of Ecology and Environment
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• v.36 no.1 s.102
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• pp.38-47
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• 2003

The water quality of the Pyeongtaek Reservoir and its main streams has been eval uated far water pollution state in March, June, September and December,2000. The following are the findings: $NH_4$ accounts for the majority of TN in the inflow streams. In the reservoir, TN and $NH_4$ are the more present in the winter season and less in the summer season, with $1.6{\sim}2.4$ times of $NO_3$ and $5.3{\sim}11.4$ times of $NO_2$ found in December and June compared with other seasons. The concentration of each component is different between streams: $NH_4$ among inorganic nitrogen has the highest concentration in the upstream, and $NO_3$ is more prevalent in the downstream. SRP accounts for $25{\sim}69%$ of TP in the stream. Unlike N component, P component in the reservoir rapidly decreases from upstream toward downstream, except in the summer. Average SRSi slightly increases in the fall, i.e., immediately after rainfall. In the streams, the average concentration of chlorophyll-a ranges from 9 to $33{\mu}g/l$, and is relatively high in the downstream. In contrast, in the reservoir, it is the highest in the upstream where $NH_4$ and SRP are frequently found. In particular, diatom and cryptomonad algae are bloomed in March, and blue-green algae in September; their maximum values are $108{\mu}g/l$ and $130{\mu}g/l$, respectively. Considering the concentration of N and P nutrients, pollution loads can affect the Pyeongtaek Reservoir in the downstream in this order: Ansong Stream

• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.605-619
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• 2019

The objective of this study was to analyze eutrophication characteristics, empirical model analysis, and variation of water quality according to monsoon intensity in Hapcheon Reservoir for 16 years from 2002 to 2017. Long-term annual water quality analysis showed that Hapcheon Reservoir was in a meso-nutrition to eutrophic condition, and the eutrophic state intensified after the summer monsoon. Annual rainfall volume (high vs. low rainfall) and the seasonal intensity in each year were the key factors that regulate the long-term water quality variation provided that there is no significant change of the point- and non-point source in the watershed. Dry years and wet years showed significant differences in the concentrations of TP, TN, BOD, and conductivity, indicating that precipitation had the most direct influence on nutrients and organic matter dynamics. Nutrient indicators (TP, TN), organic pollution indicators (BOD, COD), total suspended solids, and chlorophyll-a (Chl-a), which was an estimator of primary productivity, had significant positive relations (p<0.05) with precipitation. The Chl-a concentration, which is an indicator of green algae, was highly correlated with TP, TN, and BOD, which differed from other lakes that showed the lower Chl-a concentration when nutrients increased excessively. Empirical model analysis of log-transformed TN, TP, and Chl-a indicated that the Chl-a concentration was linearly regulated by phosphorus concentration, but not by nitrogen concentration. Spatial regression analysis of the riverine, transition, and lacustrine zones of $log_{10}TN$, $log_{10}TP$, and $log_{10}CHL$ showed that TN and Chl-a had significant relations (p<0.005) while TN and Chl-a had p > 0.05, indicating that phosphorus had a key role in the algal growth. Moreover, the higher correlation of both $log_{10}TP$ and $log_{10}TN$ to $log_{10}CHL$ in the riverine zone than the lacustrine zone indicated that there was little impact of inorganic suspended solids on the light limitation in the riverine zone.

• Journal of agriculture & life science
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• v.53 no.1
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• pp.13-21
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• 2019

This study was carried out to acquire basic data for a long-term hydroponic culture through investigating water and inorganic ion uptake characteristics at different EC level of nutrient solution of three tomato varieties. Three different tomato varieties, the European type(cv. Daphnis), the Asian type(cv. Super Doterang) and cherry type(cv. Minichal), were used for the investigation. Also, the deep flow technique(DFT) was applied. The three different electrical conductivity(EC) level(1.0, 2.0, 3.0, and 4.0 dS·m-1) of hydroponic nutrient solution were used as variable. At a high EC level of nutrient solution, the leaf area and fresh weight decreased in the early stage, and its growth(plant height, leaf number, leaf area, fresh-weight) was poor with salt stress. Result showed that the higher the EC level of the nutrient solution, the lesser was water uptake. The water uptake was not significantly different from varieties in the first survey, but In the second survey, the 'Daphnis' did not show a significant decrease in water uptake in the EC level higher than 2.0 dS·m-1., on the other hand, 'Super Doterang' presented very low water uptake. At a low EC level, N, P, and K, were absorbed more than the concentration of the irrigation water, while Ca, Mg, S uptake were low. At a high EC level, almost ions absorbed less than 50% of the initial concentration of irrigation water. Thus, imbalance among ions was severe at low EC level compared to high EC level. 'Daphnis' was a variety that effectively utilize nutrients under nutrient stress, showing high absorption at low concentration condition and low absorption at high concentration condition. However, 'Daphnis' suffered most seriously by absorbing nutrients excessively.

• Journal of Korean Society of Forest Science
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• v.53 no.1
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• pp.27-36
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• 1981

Foliar nutrient concentrations of N, P, K, Ca, Mg, total sugar, starch, ether extracts were determined for three Pinus spp., that is, P. rigida, P. taeda, P. rigida${\times}$taeda, divided by tree age (16~19-year old, 6-year old), leaf age (current, over-winter, one-year old), planting location(Kyonggi-Do, Chungnam-Do, Junbuk-Do). Foliar compositions of inorganic nutrients were generally put in order of N(0.764~1.502%)>K((0.130~0.491%) $$\geq_-$$Ca(0.165~0.442%)>Mg(0.054~0.121%)${\fallingdotseq}$P(0.041~0.129%) in all the species. The concentrations of total sugar and ether extracts respectively ranged from 5 to 15% of the needles in dry weight base. The concentrations of N, P and K were similarly high in the over-winter needles (sampled in February), but those of Ca were generally high in one-year old needles. As a whole, inorganic nutrient levels in the needles showed different patterns with species, three age, leaf age and location. There were generally positive correlations between nitrogen and phosphorus in foliar concentrations. Foliar concentrations of total sugar showed the ranking of P. rigida > P. rigida${\times}$taeda > P. taeda and the lowest levels in February. Starch in the needles were contained about 10% of total sugar, and the variations of starch level were not regular with the studied factors. Ether extracts contents increased more of less with leaf age but changed irregularly with the other factors.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.436-446
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• 2020

In this study, we verified the effects of organic amendment application based on soil testing in potato cultivation. The application rate of organic amendments was determined based on the inorganicization rate of nitrogen, phosphoric acid, and potassium in the organic amendments. There was no significant difference in the length, stalk number, stalk diameter, and leaf color of potato plants under organic amendment application compared with those under chemical fertilization. The quantity of potato tubers and yield of marketable tubers under organic amendment application were higher than those under chemical fertilization. The top fresh weight and top-to-root ratio were the highest under organic amendment application, followed by those under chemical fertilization and the control. The inorganic nitrogen content in the leaves and stems of potato plants was the highest under chemical fertilization. There was no difference in the phosphoric acid content between the potatoes under chemical fertilization and those under organic amendment application. The potassium content in potatoes was higher under chemical fertilization than that under organic amendment application. While the change trend of inorganic nitrogen content in the roots was similar to that in the leaves and stems, the potatoes under organic amendment application, with the highest yield, showed the highest dry weight. The tuber weight showed a positive correlation with plant length, stalk number, and stalk diameter. The higher the weight of the tuber, the higher the weight of the marketable tuber, and the higher the top fresh weight, the higher the yield. Therefore, to increase yield, it is necessary to supply nutrients to improve the top fresh weight to the optimal level. There was no difference in the utilization efficiency of nitrogen and potassium between the potatoes under chemical fertilization and those under organic amendment application. The utilization efficiency of phosphoric acid was increased by 0.1% in potatoes under organic amendment application compared with that under other treatments. Regarding soil chemistry after harvest, the soils under organic amendment application showed a higher electrical conductivity and higher nitrogen and phosphoric acid content than those under other treatments. Therefore, the organic amendment method used in this study can be an alternative to chemical fertilization. It is also advantageous for the cultivation of subsequent crops in potato fields.

• Korean Journal of Soil Science and Fertilizer
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• v.16 no.2
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• pp.131-155
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• 1983

Though it has been widely known the nitrogen effects are influenced by soils, varieties, and mineral nutrients in the rice culture, few analyses in relation to the factors increasing nitrogen effect have been studied in Korea. The effects of potassium and silica on the factors increasing nitrogen effects in paddy soils were investigated in accordance with soil improvement practices and nitrogen application methods for the cultivated varieties. The results obtained are as follows. 1. For 413 paddy fields, the yield from soils without nitrogen application ranged from 200 to 850kg/10a and that from nitrogen application did 350 to 1,051kg/10a. The yield increament by nitrogen application varied 50 to 650kg/10a depending on soils. 2. Soil chemical characteristics for high yield were different between with nitrogen and without nitrogen application. In the without nitrogen application, however, contents of organic matter, phosphorous, potassium and calcium of high yield soils were lower than those of low yield, while the available silica content was higher in the former. 3. The yield increased with nitrogen application up to 22.4kg/10a and thereafter it decreased. These phenomena were supposed to be not be decrease of nitrogen uptake but by lowered silica uptake. 4. Clay soil incorporation, deep plough, and inorganic constituents control such as Ca, Mg, and $Sio_2$ were effective as soil improvement praitices. It was appeared that increases of silica content and Ca/Mg ratio were important to increase nitrogen effects. 5. For the correlation between yield and yield components, it was high between yield and panicle in low nitrogen level and so was it between grain yield and ripening rate in high nitrogen. 6. In the urea and super granule urea application plot, recovery rate of nitrogen by plant and soil was high and yield was remarkable high. 7. Regardless of fertilizer types such as ammonium sulfate and urea, the residual nitrogen was about 4kg/10a in both plots of 5.8 and 11.6kg/10a. N applied. 8. The potassium application to soil enhanced the nitrogen efficiency. It was more effective in low potassium soil. 9. Optimum pH value for gel formation in the 4% sodium silicate solution was approximately 6.6. 10. It was suggested that silica could affect to rice plant growth as the inorganic and organic chemical components.

• Korean Journal of Environmental Biology
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• v.17 no.4
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• pp.529-541
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• 1999

In order to elucidate characteristics of water quality, investigation of monthly dynamics of environmental factors and algal populations at major four stations of the mid and lower part in Taechong Reservoir was performed from June 1998 to June 1999. Water temperature, DO and pH were ranged 5.3~27.7$^{\circ}C$, 6.2~13.8 mgO$_2$/1 and 6.4~9.5, respectively. Those were varying as the season changes. Among inorganic nitrogen nutrients, NH$_4$was ranged from 5.5% to 7.2% of NO$_3$and NO$_3$was almost same through the seasons except summer in which it was low. SRP and SRSi were increased in summer when the blue-green algae became dominant. Those were decreased as the cell density of diatom increased when the water temperature dropped. Therefore SRSi was considered to be another important nutrient factor contributing to the increment of biomass of freshwater algae as well as SRP. Average chi-$\alpha$ concentration ranged from s to 12 $\mu$g/1 and in the lower part or the reservoir, the lowest was found. Moreover, there were remarkable increment in summer when TN/TP ratio were decreasing from relationships between TN/TP ratio and chi-$\alpha$ concentration. Annual mean ratio of TN/TP ratio was relatively high as the value was 110, which was relatively high, and it showed that P is the dominant factor in the algal growth. The dynamics of phytoplankton were simply dominated by a few species seasonally. In summer, blue -green algae such as Anabaena, Microcystis and Oscillatoria were dominant and algal bloom of blue -green began from early summer, sustained to late autumn. The average standing crops of A. spiroides v. crassa, M. aeruginosa and O. limosa were ranged 0.3~2.0$\times$10$^4$cells/ml, 6.4$\times$10$^2$~1.0$\times$10$^4$cells/ml and 4.6$\times$10$^3$~1.6$\times$10$^4$cells/ml, respectively. In winter, diatom Stephanodiscus was considered to be an important species whose average standing crops of Stephunodiscus was 4.9$\times$10$^2$cells/ml from November to April of the next year and the highest was 1.3$\times$10$^3$cells/ml in January.