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Sangho Jeon(전상호),Min Hye Park(박민혜),Myung Sook Kim(김명숙),Tae-Gu Lee(이태구),Ha-il Jung(정하일),Jeong Gu Lee(이정구) 한국토양비료학회 2021 한국토양비료학회 학술발표회 초록집 Vol.2021 No.11
Soil organic matter (SOM) is an important indicator to assess soil fertility, health and quality. For proper managements of agricultural fields, a long-term monitoring of changes in SOM contents in field and estimation of national accumulation of SOM are required. In this study, SOM and agricultural field area of paddy and upland systems were investigated from 2013 to 2020 for all administrative provinces of South Korea. Total agricultural field area was decreased by 4.8% and 9.0% in 2016 and 2020 compared with 2013, respectively. In paddy field, SOM concentration was 23.5g kg<SUP>-1</SUP> in 2013, which was gradually increased by 2.2% in 2020. Despite that SOM concentration increased at a field scale, national SOM accumulation in paddy fields decreased due to reduced paddy area. In upland fields, SOM concentration was gradually increased by 6.5% from 2013 to 2020. Though SOM content increased, however, SOM accumulation in the total agricultural field at national scale was not affect due to less area than paddy field area. Therefore, total SOM accumulation was continuously decreased from 69.2 Tg in 2013 to 65.3 Tg in 2020 mainly due to decreasing paddy field area. This study showed that in spite of the SOM increase of both fields, national SOM accumulation is decreased with significantly decreasing total field area. In conclusion, to increase SOM accumulation, we have to apply additional organic matter or increase agricultural field area.
Pathogen Filtration in Irrigation Water
Sangho Jeon(전상호),Yeon-Kyu Sonn(손연규),Byung-Keun Hyun(현병근),Sun-Gang Yun(윤순강),Dong-Sung Lee(이동성),Wei Zhang 한국토양비료학회 2017 한국토양비료학회 학술발표회 초록집 Vol.2017 No.10
Phytophthora and Pythium are commonly known as water molds, and can cause enormous losses to many floriculture and vegetable crops worldwide, including seedling damping-off, stunting, crown, stem and root rot as well as environmental damage in natural ecosystems. It is challenging to control these pathogens because plants are infected and do not show symptoms until the disease is too advanced to respond to treatment. The pathogens can also easily develop resistance to effective fungicides. Recycled water irrigation system is getting popular in the United States and worldwide because there are benefits for both environmental and economic perspectives. However, this practical system can aggravate their transmission in the greenhouse. To deal with the problem, various physical and chemical disinfection methods have been proposed to control recirculation of contaminated nutrient solution in the greenhouse. These methods, however, have shown problems, such as high cost of installation or maintenance and environmental damage. In this regard, my first study investigated the transport and retention of Phytophthora. capsici zoospores in saturated columns packed with iron oxide coated sand (IOCS) or uncoated sand in Na<SUP>+</SUP> or Ca<SUP>2+</SUP> background solution at pH 7.2 or 4.4, in combination with XDLVO interaction energy calculations and microscopic visualizations. Significantly more encysted zoospores were retained in IOCS than in uncoated sand, and at pH 4.4 than at pH 7.2, which likely resulted from increased electrostatic attraction between zoospores and grain surface. At pH 7.2, up to 99% and 96% of the encysted zoospores were removed in IOCS and uncoated sand, respectively, due to a combination of strong surface attachment, pore straining, and adhesive interactions. Motile biflagellate zoospores were more readily transported than encysted zoospores, thus posing a greater dispersal and infection risk. The second and third studies were conducted in greenhouses to demonstrate a proof-of-concept of using fast-flow filtration to control Pythium and Phytophthora and Pythium diseases in greenhouse floriculture and vegetable crops. The second study showed that Pythium aphanidermatum could be effectively removed by the sand and AC filters during fast-flow filtration with low water pressure. The rapid sand filter had the best performance because no decrease in the poinsettia quality was observed when compared to the non-inoculated control plants. Because the AC filter can also remove the essential nutrients from the irrigation water, and cause the Fe deficiency in the poinsettias, it is less desirable to be used unless the nutrients can be supplied separately instead of through irrigation water. The third study found that the filter with iron oxide coated media [IOCM] could effectively protect the squash plants from Phytophthora capsici, but caused the nutrient deficiency in the squash. The sand filter could not prevent, but only slow the disease development in the squash. Again, it shows that the IOCM filter has the potential to be used in treating irrigation water in the greenhouse vegetable production, but the sufficient nutrients need to be provided. Overall, the results suggested that physical removal of pathogens using fast-flow filtration can overcome many limitations of fungicide application, and may be a promising alternative for disease management in the greenhouses.
Sangho Jeon,강동희,Geun Woo Lee 한국물리학회 2013 Current Applied Physics Vol.13 No.8
We report on simultaneous measurements of the emittance, transmittance and reflectance of a porous alumina under same environment at 573 K, which has not been obtained. It is demonstrated that the correction of substrate radiation and multiple reflections is important for the accurate measurement of infrared (IR) optical properties of porous materials in a two-substrate method. We deduced the extinction, absorption and scattering coefficients of the alumina from the measured three quantities,based on the classical geometry model. The coefficients explain the difference of the IR optical properties between the alumina and the sapphire. The increasing reflectance of the alumina with thickness, unlike the sapphire, is attributed to the relatively high scattering coefficient at short wavelengths.
Sangho Jeon,Kyunghwa Han,Byungkeun Hyun,Yeonkyu Sonn,Woori Go,Byunghwan Seo 한국토양비료학회 2019 한국토양비료학회지 Vol.52 No.4
Lay flat sprinkler hoses are widely use in S. Korea due to its reasonable price and flexibility. However, it applies a lot of water for a short time in a field that potentially causing unbalanced irrigation. In addition, there have been not many studies on characteristics such as irrigation uniformity. In this regards, the purpose of this study was to provide fundamental data for the design and operation of lay flat sprinkler by evaluating the irrigation uniformity and the watering pattern according to the change of water pressure. The most important characteristics for the uniformity were a pattern, number, and diameter of the holes on the lay flat sprinkler hoses. The amount of irrigation was different up to 2.3 times under the same (or about same) water pressure. Statistical uniformity (CV) of the sprinkler hose A, B, C showed good to fair, good, and fair respectively. Emission uniformity (EU) of the sprinkler hose A, B, and C classified good, excellent to good, and fair individually. The results of this study would be useful for proper water management by providing fundamental data such as water pressure level, spacing, and water management when installing lay flat sprinkler hoses in crop cultivating sites.
Micro-sprinkler Irrigation Uniformity as Affected by Different Water Pressure and Outlet Intervals
Sangho Jeon,Seonah Hwang,Yeonkyu Sonn,Byungkeun Hyun,Woori Go,Sungang Yun,Kyunghwa Han 한국토양비료학회 2018 한국토양비료학회지 Vol.51 No.4
This study carried out to evaluate the water distribution uniformity of micro-sprinkler to improve water utilization efficiency. The water quantity and the water pressure were measured according to the spacing of micro-sprinkler and adjusting the applied water pressure. The results showed that the spacing of the micro-sprinklers a decisive influence on the distribution uniformity, but the change in hydraulic pressure did not have a significant effect. The water quantity was reduced by 22.7 ± 1.6 % when the water pressure dropped 100 kPa. Each micro-sprinkler has different spray pattern. The wetted radius was measured about 4 m. A peak was found within a meter radius from the center of the micro-sprinkler and gentle slope between 2 - 4 m. The appropriate spacing is 2 - 4 m depend on micro-sprinkler and purpose of the system. The results would be used in micro-sprinkler system guideline and design for best water distribution uniformity.
Jeon, Sangho,Park, Seung-Nam,Yoo, Yong Shim,Hwang, Jisoo,Park, Chul-Woung,Lee, Geun Woo Optical Society of America 2010 Optics letters Vol.35 No.23
<P>A two-substrate method is developed to simultaneously determine emissivity, transmittance, and reflectance of semitransparent materials with a single measurement under the same environment at elevated temperature. The three quantities can be obtained through the emissivities of substrates and the apparent emissivities resulting from the radiance of the sample heated by substrates. The two-substrate method is compared with the conventional method by measuring sapphire samples with various thicknesses, resulting in good agreements for all the samples. The present method will be useful to measure the temperature dependence of optical properties of porous ceramic materials.</P>