• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.6
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• pp.43-54
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• 2018

The accurate estimation of reference crop evapotranspiration ($ET_o$) is essential in irrigation water management to assess the time-dependent status of crop water use and irrigation scheduling. The importance of $ET_o$ has resulted in many direct and indirect methods to approximate its value and include pan evaporation, meteorological-based estimations, lysimetry, soil moisture depletion, and soil water balance equations. Artificial neural networks (ANNs) have been intensively implemented for process-based hydrologic modeling due to their superior performance using nonlinear modeling, pattern recognition, and classification. This study adapted two well-known ANN algorithms, Backpropagation neural network (BPNN) and Generalized regression neural network (GRNN), to evaluate their capability to accurately predict $ET_o$ using daily meteorological data. All data were obtained from two automated weather stations (Chupungryeong and Jangsu) located in the Yeongdong-gun (2002-2017) and Jangsu-gun (1988-2017), respectively. Daily $ET_o$ was calculated using the Penman-Monteith equation as the benchmark method. These calculated values of $ET_o$ and corresponding meteorological data were separated into training, validation and test datasets. The performance of each ANN algorithm was evaluated against $ET_o$ calculated from the benchmark method and multiple linear regression (MLR) model. The overall results showed that the BPNN algorithm performed best followed by the MLR and GRNN in a statistical sense and this could contribute to provide valuable information to farmers, water managers and policy makers for effective agricultural water governance.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.1
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• pp.34-43
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• 1996

Determining the actual evapotranspiration(ETa) of a crop, and appropriate water management of the crop based on the ETa are very important For increasing the yield. The present study aimed at determining ETa and crop coefficient of sesame growing under different climatic conditions with the transparent thin polyethylene film mulch(0.03 mm thick) and without this mulch. Bottomless cylindrical lysimeters(105cm in diameter, 120cm in height, protruded 20 cm above the soil surface) were installed on the field of sandy loam "Bonyang series" soil with a moderate drainage. The determination of ETa was performed by measuring each component of a model equation, $ETa=(R+I)-\{Ro+(D1+D2)\}+C{\pm}{\Delta}S$. Sesame, cv. "Ansan" was sown in two rows with the spacing of $50{\times}15cm$ on May 10 in 1991 and 1992. The mulching covers 80% of the soil surface. Sesame consumed the water of 139.0 mm(1.53 mm/day) and 171.2 mm(1.59 mm/day) in ETa without the film mulch, but that of 132.6 mm(1.46 mm/day) and 199.8 mm(1.85 mm/day) with its mulching through both years of 1991 and 1992, respectively. The ETa's accounted for 52 and 69% of the potential evapotranspiration(ETp) in the mulched crop, and 54 and 59% of ETp in the non-mulched crop 1991 through 1992, respectively. Its ETa's were much more and their gap between the mulching and non-mulching treatment was larger in 1992 than in 1991 as a result of the better climatic condition of 1992.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.1
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• pp.93-101
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• 2008

The effects of $CO_2$ enrichment on growth of maize (Zea mays L.) were examined. Parameters analyzed include growth characteristics, yields, photosynthetic rates, evaporation rates and photosynthesis-related characteristics under elevated $CO_2$. The plants were grown in growth chambers with a 12-h photoperiod and a day/night temperature of $28/21^{\circ}C$ at the seedling stage and $30/23^{\circ}C$ from the silking stage. The plants were exposed to two elevated $CO_2$ of 500, 700ppm and ambient levels (350 ppm). Chalok 1 and GCB 70 germinated three days after seeding, and germination rates were faster in the elevated $CO_2$ than the control. Germination rates displayed significant differences among the $CO_2$ treatments. At the seedling stage, leaf area, top dry weight, and photosynthetic rates, and plant height indicated positive relationship with elevated $CO_2$ concentrations. At the $5{\sim}6$ leaf stage, $CO_2$ concentration also indicated positive relationship with plant height, leaf area, top dry weight, and photosynthetic rates. At the silking stage, increased plant height of Chalok 1 was noted in the $CO_2$ treatments compared to the control. No significant differences were noted for GCB 70, in which leaf area decreased but photosynthetic rates increased progressively with $CO_2$ concentration. Stomatal aperture was a little bigger in the elevated $CO_2$ than the control. $CO_2$ concentration was negatively related to stomatal conductance and transpiration rates, resulting in high water use efficiency.

• Korean Journal of Medicinal Crop Science
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• v.26 no.6
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• pp.447-454
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• 2018

Background: The leaf temperature ($T_{LEAF}$) is one of the most important physical parameters governing water and carbon flux, including evapotranspiration, photosynthesis and respiration. Cnidium officinale is one of the important folk medicines for counteracting a variety of diseases, and is particularly used as a traditional medicinal crop in the treatment of female genital inflammatory diseases. In this study, we developed a model to estimate $T_{Leaf}$ of Cnidium officinale Makino based on black globe temperature ($T_{BGT}$). Methods and Results: This study was performed from April to July 2018 in field characterized by a valley and alluvial fan topography. Databases of $T_{LEAF}$ were curated by infrared thermometry, along with meteorological instruments, including a thermometer, a pyranometer, and an anemometer. Linear regression analysis and Student's t-test were performed to evaluate the performance of the model and significance of the parameters. The correlation coefficient between observed $T_{LEAF}$ and calculated $T_{BGT}$ obtained using an equation, developed to predict $T_{LEAF}$ based on $T_{BGT}$ was very high ($r^2=0.9500$, p < 0.0001). There was a positive relationship between $T_{BGT}$ and solar radiation ($r^2=0.8556$, p < 0.0001), but a negative relationship between $T_{BGT}$ and wind speed ($r^2=0.9707$, p < 0.0001). These results imply that heat exchange in leaves seems to be mainly controlled by solar radiation and wind speed. The correlation coefficient between actual and estimated $T_{BGT}$ was 0.9710 (p < 0.0001). Conclusions: The developed model can be used to accurately estimate the $T_{Leaf}$ of Cnidium officinale Makino and has the potential to become a practical alternative to assessing cold and heat stress.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.229-237
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• 2019

This study was conducted to estimate annual reference evapotranspiration (ET₀) for the agro-climatic zones for rice paddy fields in South Korea between 1980 and 2015. The daily ET₀ was estimated by applying the Penman-Monteith method to meteorological data from 61 weather stations provided by Korean Meteorological Administration (KMA). The average of annual ET₀ from 1980 to 2015 was 1334.1±33.89 mm. The ET₀ was the highest at the Southern Coastal Zone due to their higher air temperature and lower relative humidity. The ET₀ had significantly increased with 2.81 mm/yr for the whole zones over 36 years. However, the change rate of it was different among agro-climatic zones. The annual ET₀ highly increased in central zones and eastern coastal zones. In terms of correlation coefficient, the temporal change of the annual ET₀ was closely related to variations of four meteorological factors (i.e., mean, minimum temperatures, sunshine duration, and relative humidity). The results demonstrated that whole Korean agro-climatic zones have been undergoing a significant change in the annual ET₀ for the last 36 years. Understanding the spatial pattern and the long-term variation of the annual ET₀ associated with global warming would be useful to improve crop and water resource managements at each agro-climatic zone of South Korea.

• Korean Journal of Remote Sensing
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• v.36 no.6_1
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• pp.1465-1483
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• 2020

Evapotranspiration is a concept that includes the evaporation from soil and the transpiration from the plant leaf. It is an essential factor for monitoring water balance, drought, crop growth, and climate change. Actual evapotranspiration (AET) corresponds to the consumption of water from the land surface and the necessary amount of water for the land surface. Because the AET is derived from multiplying the crop coefficient by the reference evapotranspiration (ET0), an accurate calculation of the ET0 is required for the AET. To date, many efforts have been made for gridded ET0 to provide multiple products now. This study presents a comparison between the ET0 products such as FAO56-PM, LDAPS, PKNU-NMSC, and MODIS to find out which one is more suitable for the local-scale hydrological and agricultural applications in Korea, where the heterogeneity of the land surface is critical. In the experiment for the period between 2016 and 2019, the daily and 8-day products were compared with the in-situ observations by KMA. The analyses according to the station, year, month, and time-series showed that the PKNU-NMSC product with a successful optimization for Korea was superior to the others, yielding stable accuracy irrespective of space and time. Also, this paper showed the intrinsic characteristics of the FAO56-PM, LDAPS, and MODIS ET0 products that could be informative for other researchers.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.2
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• pp.37-46
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• 2014

Water for crop growth were supplied by irrigation in protected cultivation and these are accumulated in the soil and utilized for crop evapotranspiration. The study for analyzing soil moisture characteristics is necessary for adequate irrigation water and soil water management in protected cultivation. Soil moisture content, irrigation water quantity and meteorological data were monitored to analyze soil moisture increment and extraction characteristics in terms of soil layers and cucumber crop growth stages. In first cropping period, the total amount of irrigation water was 5.07 mm/day, soil moisture increment was 4.82 mm/day and soil moisture extraction was 5.56 mm/day. In second cropping period, the total amount of irrigation water was 4.82 mm/day, soil moisture increment was 4.65 mm/day and soil moisture extraction was 4.73 mm/day. Soil moisture extraction rate from 0 to 75 cm is 90.3 % in first cropping period and 79.1 % in second cropping period. The majority irrigation water were consumed in root zone, however, about 15 % of soil moisture were losses by infiltration in lower soil layer. Soil moisture extraction and extraction pattern of cucumber crop calculated in this study can be utilized as a basic data for irrigation water management in protected cultivation.

• Horticulture, Environment, and Biotechnology : HEB
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• v.59 no.6
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• pp.815-826
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• 2018

The intense drought affecting olive production in Northern Chile underscores the need to research non-traditional irrigation strategies to obtain the best crop performance. Accordingly, this study aimed to obtain preliminary data to guide future research on this topic. Different water replenishment levels on crop evapotranspiration ($ET_c$ ; 13.5, 27.0, 40.5, and 54%) were established in a young orchard, cv. Arbequina, from the end of fruit drop (EFD) to full bloom in the next season. We evaluated the influence of plant water status (${\Psi}_{stem}$ ) and crop load, considered as function of fruit number divided by trunk cross-sectional area, on reproductive and productive variables using multiple linear regressions. Our results show that crop load and ${\Psi}_{stem}$ measured from EFD to harvest affected yield components. Nevertheless, ${\Psi}_{stem}$ had the strongest influence on fruit size, pulp development, oil accumulation, and yield. Oil content and yield were reduced by 54% and 50% for each MPa, respectively, from ${\Psi}_{stem\;EFD-H}$ -1.8 MPa, an effect that intensified as crop load increased. During the period of flower development (September-November), the number of flowers per inflorescence and percentage of perfect flowers were reduced when ${\Psi}_{stem}$ was less than -2.0 MPa. These preliminary results showed that bud differentiation, inflorescence and flower formation are highly sensitive to water deficit.

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.3
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• pp.107-116
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• 2020

In this data paper, we share the dataset obtained during 2019 from the test-bed to develop soil moisture estimation technology for upland fields, which was built in Seosan and Taean, South Korea on May 3. T his dataset includes various eco-hydro-meteorological variables such as soil moisture, evapotranspiration, precipitation, radiation, temperature, humidity, and vegetation indices from the test-bed nearby the Automated Agricultural Observing System (AAOS) in Seosan operated by the Korea Meteorological Administration. T here are three remarkable points of the dataset: (1) It can be utilized to develop and evaluate spatial scaling technology of soil moisture because the areal measurement with wide spatial representativeness using a COSMIC-ray neutron sensor as well as the point measurement using frequency/time domain reflectometry (FDR/TDR) sensors were conducted simultaneously, (2) it can be used to enhance understanding of how soil moisture and crop growth interact with each other because crop growth was also monitored using the Smart Surface Sensing System (4S), and (3) it is possible to evaluate the surface water balance by measuring evapotranspiration using an eddy covariance system.

• The Plant Pathology Journal
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• v.32 no.6
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• pp.508-518
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• 2016

Early blight of tomato caused by Alternaria solani, is responsible for severe yield losses in tomato. The conidia survive on soil surface and old dry lower leaves of the plant and spread when suitable climatic conditions are available. Macroclimatic study reveals that highest inoculum concentration of Alternaria spores appeared in May 2012 to 2013 and lowest concentration during January 2012 to 2013. High night temperature positively correlated and significantly (P < 0.01) involved in conidial spore dispersal and low relative humidity (RH) displayed significant (P < 0.05) but negative correlation with conidial dispersal. The objective of the study was to modify microclimatic conditions of tomato crop canopy which may hamper conidial dispersal and reduce disease severity. We evaluated effect of marigold intercropping and plastic mulching singly and in consortia on A. solani conidial density, tomato leaf damage and microclimatic parameters as compar to tomato alone (T). Tomato-marigold intercropping-plastic mulching treatment (T + M + P) showed 35-39% reduction in disease intensity as compared to tomato alone. When intercropped with tomato, marigold served as barrier to conidial movement and plastic mulching prevented evapotranspiration and reduced the canopy RH that resulted in less germination of A. solani spores. Marigold intercropping and plastic mulching served successfully as physical barrier against conidial dissemination to diminish significantly the tomato foliar damage produced by A. solani.