• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.192-199
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• 1999

In order to make the reasonable irrigation planin the reclaimed paddy fields, the estimation of irrigation water requirements by soil textures and water management methods for the normal growth of crops is very important. This study was carried out to determine leaching water requirements before cultivating crops. For the purposes of this study, the physical and chemical properties of soil sampels used in the desalinication experiments were analyzed and change of salinity by supplying water and leaching water were investigated in the experimental field with lysimeters.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.254-258
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• 1998

Distribution and occurrence of weedy rice in Kyonggi region were surveyed in 1996. Weedy rice was observed in 1368 fields (54.9%) of total 2490 fields. Almost two thirds of paddy fields in northern mountainous region were contaminated by weedy rice and more severe contamination, three forths of paddy fields, was observed in suburban regions. In those regions, occurrence of weedy rice was greater than those in north-eastern inland and south-western plain regions. The occurrence of weedy rice was higher in water seeding cultivation (66.7%) than other cultivation methods. The number of weedy rice per 10a was 756.7 plants in direct seeding on dry paddy and 379.4 plants in water seeding. The occurrence of weedy rice was higher in fields planted by farmer's seeds than that of paddy fields cultivated by certified seeds, and the longer the farmer's seeds being used, the more weedy rice occurred in paddy field.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.2
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• pp.134-142
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• 1997

This study was performed to evaluate the drain runoff characteristics from one paddy field, and to provide the basic data required for the determination of flood discharge and unit drainage water for drainage improvement and farmland consolidation. For this purpose, under the assumption that drain discharge from paddy field was similar to outflow of reservoir, runoff model based on storage equation was applied to the experimental field, and simulated results were compared to the measured discharge at weir point. To estimate effective storage volume of paddy field with water depth, 4 regression formula were examined such as linear, exponential, power, and combined. From the observed runoff characteristics, it was shown to be 3.3~16.3${\ell}$/sec in weir discharge, 57.2~98% in runoff ratio, and relative error of simulated result was 3.0~39.4%, 8.5 ~56.0 % for peak flow and runoff ratio, respectively. Curve number by SCS method was calculated as mean value of 96.4 using measured rainfall and runoff data, it was considered relatively high because paddy field has generally flooding depth contrary to the upland watershed area.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.643-646
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• 2003

We investigated concentrations and loads of nutrients in the paddy plots with conventional and environmental paddy plots in Chungbuk. Different fertilizers for basa dressing were applied to two paddy plots. There were not significantly different concentrations between two experimental paddy plots because almost same amount of fertilizers were applied to two plots. For drainage water during rainy days mean T-N concentration was lower, but mean T-P concentration was almost identical compared with respective values in flooded water.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.4
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• pp.27-42
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• 2017

The global rise in atmospheric $CO_2$ concentration and its associated climate change have significant effects on agricultural productivity and hydrological cycle. For food security and agricultural water resources planning, it is critical to investigate the impact of climate change on changes in agricultural productivity and water consumption. APEX-Paddy model, which is the modified version of APEX (Agricultural Policy/Environmental eXtender) model for paddy ecosystem, was used to evaluate rice productivity and evapotranspiration based on climate change scenario. Two study areas (Gimjae, Icheon) were selected and the input dataset was obtained from the literature. RCP (Representitive Concentration Pathways) based climate change scenarios were provided by KMA (Korean Meteorological Administration). Rice yield data from 1997 to 2015 were used to validate APEX-Paddy model. The effects of climate change were evaluated at a 30-year interval, such as the 1990s (historical, 1976~2005), the 2025s (2011~2040), the 2055s (2041~2070), and the 2085s (2071~2100). Climate change scenarios showed that the overall evapotranspiration in the 2085s reduced from 10.5 % to 16.3 %. The evaporations were reduced from 15.6 % to 21.7 % due to shortend growth period, the transpirations were reduced from 0.0% to 24.2 % due to increased $CO_2$ concentration and shortend growth period. In case of rice yield, in the 2085s were reduced from 6.0% to 25.0 % compared with the ones in the 1990s. The findings of this study would play a significant role as the basics for evaluating the vulnerability of paddy rice productivity and water management plan against climate change.

• KCID journal
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• v.7 no.1
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• pp.36-46
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• 2000

An automatic inlet and a semi automatic inlet were developed for the optimal supply of irrigation water in the paddy field. The automatic inlet checks the water level in the paddy field and operates automatically by combination of two floats. In case of t

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.5
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• pp.95-105
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• 2021

Drought is a disaster that causes prolonged and wide scale damage. Recently, the severity and frequency of drought occurrences, and drought damage have been increased significantly due to climate change. As a result, a quantitative study of drought factors is needed to better understand and prevent future droughts. In the case of agricultural drought, several existing studies examine the economic damage caused by droughts and their causes, but these studies are not well suited to estimating crop-oriented agricultural drought damage and the factors that absolutely affect agricultural drought. This study determines which factors most affect agricultural drought. It examines meteorological factors and those related to agricultural water supplied by irrigation facilities. Rice paddy production per unit area is lower than the average from the last two years where agricultural drought occurred. We compare the relative frequency of agricultural drought impacts with irrigation facilities, effective reservoir storage, the number of water supply facilities, and the meteorological drought index such as Standardized Precipitation Index (SPI). To identify factors that affect agricultural drought, we correlate rice paddy production anomalies with irrigation water supply for the past two years. There was a high positive correlation between rice paddy production and irrigation water usage, and there was a low or moderate negative correlation between rice paddy production anomalies compared to the average of the past two years and SPI. As a result, agricultural water supply by irrigation facilities was judged to be more influential than meteorological factors in rice paddy production. This study is expected to help local governments establish policies related to agricultural drought response.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.445-450
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• 2001

The objective of this study is to develop the GLEAMS-PADDY model for nutrients loading simulation from paddy-field areas. This model is developed by modifying the GLEAMS model. The model is composed of hydrology, sediment and chemical parts. The model was evaluatd using field data. The model estimates water balance and nutrients concentrations reasonably well. The model can be applied to find BMP's in the paddy areas.

• Korean Journal of Environmental Agriculture
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• v.19 no.5
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• pp.433-441
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• 2000

A feasibility study was performed to examine the agronomic application of treated sewage on paddy rice culture by field experiment for two consecutive years. The domestic sewage was treated by the constructed wetland system which was in subsurface flow type and consisted of sand and macrophyte. The effluent of the wetland system was used for irrigation water. The effluent was diluted to maintain the total nitrogen concentration below $26mg{\cdot}L^{-1}$ in the first year and used without dilution in the second year experiment. Growth components and yields were compared against the CONTROL plot where conventional method was applied. And also, soil characteristics of the plots before and after reclaimed sewage irrigation were analyzed. Generally, addition of the treated sewage to the irrigation water showed no adverse effects on paddy rice culture, and even enhancement was noticed in both growth and yield. Irrigation of treated sewage after concentration adjusted with conventional fertilization showed the better result, and the yield exceeded that of CONTROL case where clean water was irrigated. Soil characteristics changed after irrigation, and significant EC increasing was observed for the reclaimed sewage irrigation plots. From this study, it appears that reuse of treated sewage, as supplemental irrigation water could be a feasible and practical alternative. For full-scale application, further study is recommended on the specific guideline of major water quality components in treated sewage for irrigation and public health.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.651-656
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• 1999

This study was carried out to investigate the paddy soil and water quality in Boryung freshwater reservoir watershed during the non-cropping season. Soil pH of the Boryung freshwater reservoir watershed were 5.39∼5.78. Total-N and P contents were high by the accumulation of chemical fertilizer partly. Heavy metal content of paddy soils were natural background level. Water pH of the Boryung freshwater reservoir watershed ranged from 6.82 to 8.64. Total-N content affected by a livestock wastes and sewage water were the higher than that of others and total-P content showed below 0.1mg/L. Nitrate nitrogen contents was very high according to the influence a livestock waste and sewage water partly. Heavy metal contents of wateers were natural background level.