• ALGAE
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• v.32 no.4
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• pp.285-308
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• 2017

Cochlodinium polykrikoides red tides have caused great economic losses in the aquaculture industry in many countries. To investigate the roles of metazooplankton in red tide dynamics of C. polykrikoides in the South Sea of Korea, the abundance of metazooplankton was measured at 60 stations over 1- or 2-week intervals from May to November 2014. In addition, the grazing impacts of dominant metazooplankton on red tide species and their potential heterotrophic protistan grazers were estimated by combining field data on the abundance of red tide species, heterotrophic protist grazers, and dominant metazooplankton with data obtained from the literature concerning ingestion rates of the grazers on red tide species and heterotrophic protists. The mean abundance of total metazooplankton at each sampling time during the study was 297-1,119 individuals $m^{-3}$. The abundance of total metazooplankton was significantly positively correlated with that of phototrophic dinoflagellates (p < 0.01), but it was not significantly correlated with water temperature, salinity, and the abundance of diatoms, euglenophytes, cryptophytes, heterotrophic dinoflagellates, tintinnid ciliates, and naked ciliates (p > 0.1). Thus, dinoflagellate red tides may support high abundance of total metazooplankton. Copepods dominated metazooplankton assemblages at all sampling times except from Jul 11 to Aug 6 when cladocerans and hydrozoans dominated. The calculated maximum grazing coefficients attributable to calanoid copepods on C. polykrikoides and Prorocentrum spp. were 0.018 and $0.029d^{-1}$, respectively. Therefore, calanoid copepods may not control populations of C. polykrikoides or Prorocentrum spp. Furthermore, the maximum grazing coefficients attributable to calanoid copepods on the heterotrophic dinoflagellates Polykrikos spp. and Gyrodinium spp., which were grazers on C. polykrikoides and Prorocentrum spp., respectively, were 0.008 and $0.047d^{-1}$, respectively. Therefore, calanoid copepods may not reduce grazing impact by these heterotrophic dinoflagellate grazers on populations of the red tide dinoflagellates.

• Research in Plant Disease
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• v.14 no.2
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• pp.79-84
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• 2008

A wilt disease on lettuce was observed in 2006 and 2007 in commercial plastic house at main production areas of lettuce in Icheon, Yongin and Goyang of Gyeonggi Province. The disease was characterized by the wilting of lower leaves, accompanied by stunting symptoms of the whole plants. Old affected stems showed the black streak in the vascular system. The pathogen, Fusarium oxysporum f. sp. lactucae was isolated from stems and roots of diseased plants. Isolated pathogen also produced the microconidia and macroconidia with chlamydospores on carnation leaf agar medium. The pathogen easily invaded and made many chlamydospores on the roots of lettuce and also made dark streaking through the vascular in the lettuce stems. The density of Fusarium sp. in the severely diseased field soil was more higher populations than that in the healthy and less diseased field soil. The minimum population of pathogen would be above $10^3$cfu/g soil to induce the Fusarium wilt on lettuce in plastic house. The results of pathogenicity test showed 'Sunpung' and 'Mipungpochap' was high susceptible to Fusarium pathogen isolates while some cultivar 'Mihongjeokchukmyeon' and 'Jinjachukmyeon' showed moderate resistance. Disease development for some lettuce was related to treated temperature, so the symptom was more severe above $25^{\circ}C$. Selection of appropriate lettuce cultivar and planting time should be related for the successful control of Fusarium wilt.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.216-216
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• 2017

Primed seeds germinate faster and uniformly, since these have already started imbibition and metabolism requiring to complete germination. Several factors such as solution composition, osmotic potential, and treatment duration affect seed priming response. Water potentials of priming solution and germination response of primed seed were investigated to clarify the effects different inorganic salt types and the duration. Pepper seeds were primed in osmotic solutions that were osmotic potential ranged -1.54 to -0.45 MPa in an aerated solution of polyethylene glycol 8000 (PEG; 17%, 22%, 27%), and inorganic salt solution of $KNO_3$, $K_2SO_4$, and $Na_2SO_4$ (100, 200, 300mM) in aerated condition. The seeds were treated at $20^{\circ}C$ for 4, 6 day (D) and stepwise duration combined concentration of 100mM (2 or 4 days) and 300mM(2 or 4days). After soaking treatment, seeds were washed with distilled water and then were dried to approximately 6% moisture content in dry chamber at $25^{\circ}C$. The germination of seed was characterized by ISAT rules at $20^{\circ}C/30^{\circ}C$ and $15^{\circ}C$. Total germination percentage (GP), mean germination time (MGT), germination uniformity (GU), germination rate (GR), and health seedling percent (HS) were calculated on the germinated seed in a 14-day period. Seed water potential (${\psi}$) was correlated with water potential of priming solution ($r^2=0.84$). The effect of seed priming on germination varies with inorganic salt and organic agents (PEG). Germination percentage (GP, 77 and 73%), GR (21.3 and $19.4 %{\cdot}day^{-1}$), and HS (58 and 52 %) was greatest and lowest MGT (4.2 and 4.8 day) when they were primed in 100mM $K_2SO_4$ (${\psi}=-0.45MPa$), and 100mM $KNO_3$ (${\psi}=-0.52MPa$) for 6 days compared to untreated control (67% GP, $19.7%{\cdot}day^{-1}\;GR$, 18% HS, and 10.8 day MGT) in $15^{\circ}C$ chamber. Water potential less then -1.2MPa of osmotic solution resulted lower GP, GR and HS and in $K_2SO_4$ and $KNO_3$. However, stepwise treatment of water potential that changed solution as 100mM for 4 D + 300mM for 2 D or 300mM for 4 D + 100mM for 2 D) were not better than single concentration alone in germination characteristics.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.316-316
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• 2017

The objective of this study is to estimate quantitatively soil salinity and soil loss at upland soils in agriculture land region in Saemangeum reclaimed land on the south Korea coasts. Soil loss and soil salinity are the most critical problem at reclaimed tidal saline soil in Korea. The several thematic maps of research area such as land cover map, topographic and soil maps, together with tabular precipitation data used for soil erosion and soil salinity calculation. Meteorological data were measured directly as air temperature, wind speed, solar radiation, and precipitation. The experiment was conducted 2% sloped lysimeter ($5.0m{\times}20.0m$) with 14 treatments and it were separated by low salinity division (LSD) and high salinity division (HSD) install. The cation content in ground water increased during time course, but in the case of land surface water the content was variable, and $K^+$ was lower than that of $Na^+$ and $Mg^{2+}$. At the LSD under rainproof condition, the salinity was directly proportional to soil water content, but at the HSD the tendency was no reversed. In condition of rainproof, the amount of soil salinity was higher at the HSD than at the LSD. Positive correlation was obtained between the soil water content and available phosphorous content at the rainfall division, but there was no significance at the surface soil of the rainproof division. Sodium adsorption ratio and anion contents in soil were repressed in the order of vinyl-mulching > non-mulching > bare field. According to the result of analyzing soil loss, soil loss occurred in a vinyl-mulching, a non-mulching and a bare field in size order, and also approximately 11.2 ton/ha soil loss happened on the reclaimed land area. The average soil loss amount by the unit area takes place in a non-mulching and bare field a lot. Our results indicate that soluble salt control and soil erosion are critical at reclaimed tidal saline soil and the results can provide some useful information for deciding management plans to reduce soil loss and salt damage for stable crop production and diverse utilization or cultivation could be one of the management options to alleviate salt damage at reclaimed tidal saline soil in Korea.

• Journal of Korean Society of societal Security
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• v.2 no.4
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• pp.43-48
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• 2009

During the past few years, Korea has experienced extraordinary floods, which have caused many damages of lives and properties. Flooding caused by typhoon is the most common disastrous phenomenon of nature among all catastrophes. As the average temperature of the earth has been increasing by global warming, the possibility of typhoon is also increased by abnormal climate changes. Along with the river improvement as a part of flood control, the time of concentration has been decreased, so the pick discharge has been increased. Moreover, with the land development activities, the area of storage has been diminishing, and the damages from inundation have been continuously increasing. There were a lot of damages to farmland in 1960's, industrial and public facilities in 1970's, and a lot of sufferings from the windstorm in 1980's. In 1990's, however, the amount of damages was increased substantially. So, there is need to decrease the number of the victims and loss of properties by applying preventive measures against natural calamities. This study has employed a simulation system to calculate the depth and amounts of inundation areas to forecast and prevent from flood damage by using rainfall-runoff model. In this study, a case study method is adopted to show inundation by using rainfall-runoff model, HEC-GeoRAS and Arcview. It is hoped that, this study would be conducive to professionals and organizations working in the field of disaster management.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.595-604
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• 2006

The growth characteristics of Commercially Developed Nitrifying Bacteria (CDNB) were studied in laboratoryscale. CDNB, a pure, artificially isolated bacterium, was cultivated to produce Cultivated Nitrifying Bacterium Group (CNBG). The average ammonia removal rate of CDNB was 0.0234g $NH_4^+-N/g$ MLSS/hr. CNBG was produced in the batch reactor and Specific Nitrification Rate (SNR) was determined at 0.0107g $NH_4^+-N/g$ MLSS/hr. The SNR of CNBG was lower than the SNR of CDNB because the diverse and multi-cultured microbial growth took place during cultivation. The effect of the temperatures and the mixing ratios of sewage and culture solution on the SNR of CNBG was studied. The SNR of CNBG, 0.0107g $NH_4^+-N/g$ MLSS/hr at $27^{\circ}C$, decreased to 0.0048g $NH_4^+-N/g$ MLSS/hr at $15^{\circ}C$, and temperature coefficient (${\Theta}$) was calculated to be 1.07. With the varied sewage mixing ratios, the SNR of CNBG remained unchanged. Activated sludge reactors maintaining an MLSS of 2,000mg/L at HRT of 4 h were operated under conditions in which dosage of Concentrated CNBG Solution (CCNBGS, 10,000mg MLSS/L) and application method of CNBG were varied. The reactor with 20mL of CCNBGS took shorter time to oxidize $NH_4^+-N$ reaching 1mg/L than the reactor with 5mL of CCNBGS showing that higher dosages were associated with greater mass removal of $NH_4^+-N$. However, the total removal was not great. In terms of different methods of CNBG application, reactor seeded with 20mL of CCNBGS took 3days to reach 1mg/L of effluent ammonia concentration while reactor dosed with 20% (v/v) CNBG implanted media took 2days. Both the control reactor and the reactor dosed with 20% (v/v) media only did not reach 1mg $NH_4^+-N/L$ after operating 18days. The reactor with CNBG implanted media had the highest $NH_4^+-N$ removal rate because of maintaining high concentration of Nitrifying Oxidizing Bacteria (NOM), and is regarded as an appropriate method for the activated sludge process.

• Journal of Food Hygiene and Safety
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• v.26 no.4
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• pp.342-348
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• 2011

The quality properties of peeled ginger (PG) were investigated during CA storage at different $CO_2$ concentrations. $O_2$ concentration was kept constant at 5% while $CO_2$ of 6%, 14%, 22% and 30% were used. It was found that the weight loss rate tended to decrease with an increase of $CO_2$. In the case of fixed $10^{\circ}C$ storage, the L-value and a-value of the exterior color in treatment increased more than that of control with respect to time, while the b-value of the exterior color and the cutting plane color showed no significant difference. In the exterior color, the results of PG-$25^{\circ}C$ showed similar with PG-$10^{\circ}C$ except b-value of the exterior color which showed not a little change. The cutting plane color did not showed significantly difference in the PG samples between $25^{\circ}C$ and $10^{\circ}C$. Hardness of the PG during storage was found to decrease most severely at 6% of $CO_2$ concentration regardless of storage temperature. The growth of microorganisms during storage of the PG tended to be restrained as $CO_2$ concentration increased. However, microorganisms, when maintained at $25^{\circ}C$ storage, multiplied rapidly to $10^8$ CFU/g within 4 days regardless of concentration.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.4
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• pp.615-620
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• 2013

To extend the shelf-life of salted Chinese cabbages, electrolyzed water (EW) was used to wash raw Chinese cabbages before the salting process (to control microbial growth), and different storage temperatures evaluated (0, 4, and $10^{\circ}C$). A tap water washing group (TW) was used for comparison. The initial total bacterial population was 5.36 log CFU/g in the TW treatment and 3.50 log CFU/g in the EW treatment. The EW treatment decreased bacterial numbers by approximately 2 log CFU/g compared to the TW treatment and kept this initial population number for 32 days at $0^{\circ}C$. The salinity had no difference during storage. In general, several factors (pH, reducing sugars, hardness, and transmittance) decreased over time, and decreased slowly with EW treatment and $0^{\circ}C$ storage. Overall, the salted Chinese cabbages with EW treatment showed lower bacterial populations compared to TW treatment, and when stored at $0^{\circ}C$, delayed decreases in quality.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.6
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• pp.811-815
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• 2006

The objective of this study was to evaluate the effect of electric fan installation for milk production improvement of dairy cattle in Thailand. The study was conducted using 2 small-holder dairy farms in Chiang Mai province, during April to August 2004. Electric fans were installed in front of each row of cows. Each of the two rows of cows in the barn was defined as an experimental unit, thus each farm had two experimental units. The fans were operated alternately in 7-day intervals between rows of cows within each farm during the day or between 8.00 am to 8.00 pm. Non-operation periods were used as control. Milk yields were recorded. Data on environmental temperature and humidity were obtained from Chiang Mai Meteorological Center. Result from statistically analysis of milk record suggested an interaction between lactation period and fan installation. Therefore, this interaction term of lactation period and fan installation (PERIOD_FAN) was added as a variable to the regression model. Due to the repeated data collection of milk yield from the same cow (alternate week), milk yield was analyzed by repeated measure analysis (Mixed model). Least square means were calculated for all levels and used to compare between each pair-wise values. The final data were collected from the total of 18 cows with 2,072 data. Overall means and SEM of milk yields and days in milk separated into farm were $14.7{\pm}0.06kg/day$ and $176.3{\pm}2.2days$, and $15.2{\pm}0.22kg/day$ and $202.5{\pm}3.7$ days for farm A and farm B, respectively. For multivariable analysis, only PERIOD_FAN and humidity were significantly associated with milk yield. Only the first period of lactation showed that the amount of milk yields during fan installation was higher than that of non-fan installation (p<0.05). Cows with fan installation produced approximately 1.2 kg/cow more milk than cows without fan installation during this period. In conclusion, the use of electric fan operated during the day time increased milk production of cows during the first period of lactation.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.4
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• pp.86-92
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• 2000

This study was conducted to determine the optimal mixing ratio of the paper mill sludge(PMS) and pig manure(PM). Since the former contains lots of total carbon and low nitrogen, it was used as carbon source. Also, dried paper mill sludge(DPMS) was added to the mixture to control the water content. The treatments was composed of four as follows, PMS-100(PM 0%+PMS 80%+DPMS 20%), PMS-85(15+65+20), PMS-70(30+50+20), and PMS-55(45+35+20). The mixtures were composted under aerobic condition in $1.25m^3$ static piles. The piles were aerated for 15 minutes per day and turned over the mixture once a week at the early stage of composting. To estimate the maturity of composts, the changes of physico-chemical properties such as temperature, pH, C/N ratio and color were monitored every week. The 25-30 and 55-60% as optimal condition of C/N ratio and moisture content were respectively recommended for effective composting by the evaluation of the changes of phsico-chemical properties for materials taken from compost files during the composting period. When the 30 and 45% of PM were mixed with PMS, the maturity time at least demanded to the stable state were shortened and the qualify of the final product was improved in a view of nutritional components.