• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1194-1196
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• 2003

Variations in soil physical and chemical properties can affect agricultural productivity and the environmental implications of crop production. These variations are present and may be important at regional, field, and sub-field (precision agriculture) scales. Because traditional measurements are time-consuming and expensive, reflectance-based estimates of soil properties such as texture, organic matter content, water content, and nutrient status are attractive. Soil properties have been related to reflectance measured with laboratory, in-field, airborne, and satellite sensors. Both multispectral and hyperspectral instruments have been used, with both natural and artificial illumination. Varying levels of accuracy have been obtained, with the best results (r > 0.95) using hyperspectral reflectance data to estimate soil organic matter and water content.

• KSBB Journal
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• v.18 no.4
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• pp.249-254
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• 2003

Experiments were carried out to select an industrial nitrogen source and optimize erythritol production by Candida magnoliae in fed-batch culture. Among the industrial nitrogen sources tested, light steep water (LSW) was found to be the best nitrogen source for producing erythritol, based on erythritol yield and raw material price. The maximum erythritol concentration obtained a 131.6 g/L, with a 52.6％ yield and 0.52 g/L-hr productivity from a 250 g/L glucose and 43.3 mL/L LSW in batch culture. Two-stage fed-batch culture was chosen to improve the volumetric productivity and the yield of erythritol. High cell density culture in cell growth stage was achieved by batch type culture containing 100 g/L glucose and 500 mL/L LSW. The cell concentration was 71.0 g/L after 23 hours of culture. Erythritol productivity was decreased by increasing glucose concentration in the production stage. But 37.3％ of the maximum erythritol yield was obtained with 185.5 g/L of erythritol and 1.66 g/L-hr of productivity when 820 g of glucose powder was directly added to a concentration of 450 g/L glucose in production stage.

• Fisheries and Aquatic Sciences
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• v.24 no.7
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• pp.260-275
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• 2021

Aquaponics is a cultivation system that combines aquaculture and agricultural hydroponics. This study investigated the productivity of leafy vegetables cultivated in the hybrid biofloc technology-aquaponics (HBFT-AP) using Japanese eel fed two kinds of diets (Mash, commercial powdered feed and extruded pellet [EP]) and hydroponics (HP).The mash was fed to the fish in a type of a dough mixed with water for 6 weeks (Exp1) and switched to the EP containing 2.7% monobasic potassium phosphate (MKP) for subsequent 6 weeks (Exp2). Leafy vegetables of 8 cultivar were employed in the experiment and water quality [dissolved oxygen (DO, mg/L), pH, water temperature (℃), electrical conductivity (EC; ㎲/cm), turbidity (NTU), TAN (NH₃ + NH₄⁺) (mg /L), NO₂-N (mg/L), NO₃-N (mg/L) and PO₄-P (mg/L)] was measured 6 times a week. Leafy vegetable productivity (HBFT-AP vs HP) was compared in respective experiment, which was similar or somewhat higher in HBFT-AP. During the 12-week feeding trial, concentrations of nitrite (NO₂-N) and phosphorus (PO₄-P) were kept low in variability while total ammonia nitrogen (TAN) and NO₃-N levels increased with time in HBFT-AP. At the end of two feeding trials, values of weight gain (WG, %), feed efficiency (FE, %), specific growth rate (SGR, %) and protein efficiency ratio (PER) were higher in Exp2 than in Exp1. As well, higher values in hematocrit (PCV, %), plasma K (mEq/L) and inorganic phosphorus (mg/dL) were found (p < 0.05) in Exp2 where fish were fed the EP (EP: 38.60%, 2.80 mEq/L and 7.04 g/dL; Mash: 33.20%, 1.95 mEq/L and 5.50 g/dL). Leafy vegetables in HBFT-AP using Japanese eel fed the EP with MKP 2.7% had a productivity similar (4 kinds of cultivar) or somewhat higher (4 kinds of cultivar) compared to those in HP. Also, Japanese eel fed the EP showed higher values of Pi (m/dL) and K (mEq/L) in plasma compared to those fed commercial powder diet.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2019.08a
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• pp.150-150
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• 2019

• Korean Journal of Ecology and Environment
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• v.52 no.2
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• pp.81-93
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• 2019

Phytoplankton is one of the important primary producers providing organic matter through photosynthesis in aquatic environments. In order to determine a temporal and spatial variation in primary productivity after weir construction in the Nakdong River, we investigated carbon uptake rates using in-situ $^{13}C$ labeling experiments and identified algal communities contributing to primary productivity using HPLC-CHEMTAX analysis from October to December, 2017. The primary productivity gradually decreased from fall to early winter season ($249{\sim}933mgC\;m^{-2}d^{-1}$ in October, $64{\sim}536mgC\;m^{-2}d^{-1}$ in November and $60{\sim}274mgC\;m^{-2}d^{-1}$ in December, respectively). This is attributed to the temporally declining light intensity and the decreasing biomass and physiological activity of phytoplankton in winter. The contribution of diatoms to the phytoplankton community in the Nakdong River was approximately 63% at all the sampling sites and seasons, while the contribution of cryptophytes increased from 9% in October to 32% in November and December. The temporal changes in the primary productivity and the dominant phytoplankton species in the mid and downstream weirs of the Nakdong River was investigated for the first time, after construction of the weirs, and major environmental factors controlling the temporal variation in primary productivity and phytoplankton communities were identified in this study. We suggest that seasonal field investigations will provide further information on the major environmental factors which affect the annual variation of primary productivity and phytoplankton communities.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.3
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• pp.369-385
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• 1996

The eco-hydrodynamic model was used to estimate the primary productivity of the oyster culture grounds in Kamak Bay. It is composed of the three-dimensional hydrodynamic model for the simulation of water flow and ecosystem model for the simulation of phytoplankton. The ecosystem model was applied to simulate phytoplankton biomass during culturing period in condition of no oyster culture grounds. The field surveys were conducted from May, 1994 to March, 1995 in Kamak bay. The results showed the concentration of chlorophyll $\alpha$ to be $1.00\~23.28\;{\mu}g/l$ in the surface layer, $1.27\~29.97\;{\mu}g/l$ in the middle layer and $1.23\~23.08\;{\mu}g/l$ the bottom layer. In monthly variations of chlorophyll $\alpha$ concentration, very high concentration were found in July, 1994 and very low concentrations in December, 1994. As the results of three-dimensional hydrodynamic simulation, the computed tidal currents ave mainly toward the inner part of bay through Yeosu Harbor and the southern mouth of a bay during the flood tide. The computed residual currents were dominated southward in Yeosu Harbor and eastward in the mouth of bay and also showed strong clockwise water circulation at the mouth of bay. The pattern between the simulated and observed tidal ellipses at three stations was very similar. The mean relative errors of all levels between the simulated and observed phytoplankton biomass at 14 stations in Kamak Bay were $13.81\%,\;9.31\%\;and\;17.84\%$, respectively. The results of phytoplankton biomass simulation showed that the biomass increased from June to September and rapidly decreased to December and then slowly increased to March. Primary productivity was estimated in the range of $0.99\~10.20gC/m^2/d$ with the average value of $4.43gC/m^2/d$ in condition of no oyster culture grounds. Primary productivity was rapidly increased from lune to August and rapidly decreased to December and then slowly increased from January to March in Kamak Bay.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.3
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• pp.164-170
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• 2005

To investigate the aquatic environmental factors and processes controlling primary production in the Seomjin River estuary, chlorophyll a, nutrients, pH, SS, DO, temperature, salinity and primary productivity were measured in February, April, August and October, 2001. Primary productivity values ranged between 50.7 and 14,120.3 mg C $m^{-3} day^{-1}$ during the sampling period. In contrast to other estuaries, light condition did not seem to be the important limiting factor far primary production due to high water-column transparency during most of the time. The autumn bloom occurred in regions where salinity values ranged between 10 and 20 psu. This phenomenon appeared to develop every year and deserves further investigation. The behavior of nutrients, which is one of the major factors controlling the primary productivity, appeared to be governed by salinity regimes. The main source of nitrogenous nutrients seemed to be the freshwater runoff from the Seomjin River. However, that of phosphorus seemed to be from the industrial wastewater in Gwangyang area. The primary pro-duction of phytoplankton in the study area varied with space and time, showing a close correlation with water column transparency, and exhibited higher values compared to those of adjacent coastal regions in Gwangyang Bay.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.126-126
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• 2022

Climate change has continued to impact meteorological factors like rainfall in many countries including Nigeria. Thus, altering the rainfall patterns which subsequently affect the crop yield. Maize is an important cereal grown in northern Nigeria, along with sorghum, rice, and millet. Due to the challenge of water scarcity during the dry season, it has become critical to design appropriate strategies for planning, developing, and management of the limited available water resources to increase the maize yield. This study, therefore, determines the quantity of water required to produce maize from planting to harvesting and the impact of drought on maize during different growth stages in the region. Rainfall data from six rain gauge stations for a period of 36 years (1979-2014) was considered for the analysis. The standardized precipitation and evapotranspiration index (SPEI) is used to evaluate the severity of drought. Using the CROPWAT model, the evapotranspiration was calculated using the Penman-Monteith method, while the crop water requirements (CWRs) and irrigation scheduling for the maize crop was also determined. Irrigation was considered for 100% of critical soil moisture loss. At different phases of maize crop growth, the model predicted daily and monthly crop water requirements. The crop water requirement was found to be 319.0 mm and the irrigation requirement was 15.5 mm. The CROPWAT 8.0 model adequately estimated the yield reduction caused by water stress and climatic impacts, which makes this model appropriate for determining the crop water requirements, irrigation planning, and management.

• ALGAE
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• v.23 no.3
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• pp.241-250
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• 2008

Since seagrasses in the coastal and estuarine ecosystems achieve high levels of production, they require high inorganic carbon and nutrient incorporation. Thus, seagrasses may play a significant role in carbon and nutrient cycling in the coastal and estuarine ecosystems. To examine growth dynamics of Zostera marina L. environmental factors such as underwater irradiance, water temperature, and salinity, and biological parameters such as shoot density, biomass, shoot morphology, and leaf productivity were measured in two bay systems (Jindong Bay and Gamak Bay) on the southern coast of Korea. While underwater irradiance did not show distinct seasonal trend, water temperature at both sites exhibited clear seasonal trend throughout the experimental period. Shoot density increased dramatically during winter due to the increased seedlings through germination of seeds in Jindong Bay and due to the increased lateral shoots in Gamak Bay. Eelgrass biomass increased during winter and decreased during summer. Maximum biomass in Jindong Bay and Gamak Bay was 250.2 and 232.3 g dry weight m–a2, respectively. Carbon incorporation into the eelgrass leaf tissues was estimated from productivity and leaf tissues carbon content. The calculated annual carbon incorporations at the Jindong Bay and Gamak Bay sites were 163 and 295 g C m–`2 y–`1, respectively. This high carbon incorporation into seagrass tissues suggests that seagrass habitats play an important role as a carbon absorber in the coastal and estuarine ecosystems.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.411-417
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• 1999

This study was performed to figure out an optimum water environment and to obtain the fundamental data related with saving labor and water consumption for the chinese cabbage being grown in greenhouse . The productivity of cabbage cultivated in boty pots and floor were compared to each other in the aspects of height and weight depending on the soil saturation levels. Obtained results are as follows. ; In case of pot cultivation , the height as well as weight of cabbage in 80% soil saturation level(P80) were measured to be larger than those in the other 2 soil saturation leves (P100 and P60). The weight of floor cultivated cabbages were relatively larger than that of pot cultivated ones. In accordance with saturation ration, the general trend of water consumption rate was maximum in P80 and was decreased in the order of P80 , P100 and P60. And the average indoor temperature as well as the plant growth rate were found to be closely related with water consumption rate.