• Korean Journal of Agricultural and Forest Meteorology
• /
• v.11 no.3
• /
• pp.100-110
• /
• 2009

'Hongro' is one of the important mid-season apple cultivars bred in Korea. The recent occurrence of water core in Hongro and the consequent problems motivated this study. The objectives of our study were to investigate the influence of air temperature during the growing period on water core occurrence in Hongro and to provide methods to mitigate its impact. Based on our field experiments for three years, the results indicated that the occurrence of water core disorder was due to the prolonged exposure to high temperature ($T_a$) of >$30^{\circ}C$ during the ripening period. The rates of occurrence of water core disorder were higher in the fruit whose weight was more than 300g or those located outside the tree canopy and thus exposed to stronger solar radiation. In terms of mitigating the water core occurrence, the application of spraying $CaCl_2$ four times from late July to August was effective. Furthermore, between 1 and 15 August when the rate of occurrence was high with $T_a$ (from 3:00 to 5:00 p.m.) >$30^{\circ}C$, the micro-water sprinkling for 30 minutes starting at 6:00 p.m. with a supplementary spray conducted two hours after the first application drastically reduced the water core occurrence.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.2
• /
• pp.198-203
• /
• 2012

Leguminous cover crops fix nitrogen from the atmosphere. The objective of this research was carried out to decrease fertilizer amount by cover crops-wheat mixtures cultivation. Field experiment was conducted at upland soil 2008 to 2009. Cover crops were used crimson clover and hairy vetch. Treatments consisted of three wheat-crimson clover (wheat 10 kg + crimson clover 1, 3, $5kg\;10a^{-1}$), wheat-hairy vetch mixture (wheat 10 kg + hairy vetch $2kg\;10a^{-1}$), and wheat - hairy vetch mixture - crimson clover (wheat 10 kg + hairy vetch 2 kg + crimson clover $3kg\;10a^{-1}$). These treatments were divided into no fertilizer and top dressing. The yield of wheat and crimson clover mixtures had no significantly differences compared to wheat only at top dressing plots. Also soil chemical and physical properties were a little bit improved such as OM, $NO_3$-N, and bulk density etc by wheat-crimson clover mixtures. Therefore, we suggested that crimson clover and wheat mixture could be used to reduction of fertilizers amount for environmental friendly wheat production.

• Korean journal of applied entomology
• /
• v.47 no.4
• /
• pp.395-400
• /
• 2008

Economic injury levels (EILs) and economic threshold (ET) were estimated for the two spider mite, Tetranychus urticae Koch (Acari, Tetranychidae) on greenhouse eggplants. T. urticae density increased until the mid-July and thereafter decreased in all plots where initial density of the mite were different each 0, 2, 5, 10 and 20 adults per plant was innoculated on June 7. Growth variables of were not different among experimental plots but fruit weights were lower in plots with higher initial mite density than in plots with lower initial mite density. Total number of fruits and the number of marketable fruits decreased in plots with higher initial mite density. The rates of yield loss increased with increasing initial mite density, resulting in 0, 3.9, 11.3, 14.5, 22.8% reduction in each of the above plots, respectively. The relationship between initial T. urticae densities and yield losses was well described by a linear regression, Y = 1.085X + 2.474, $R^2$ = 0.9659. Based on the relationship, the number of adults per plant which can cause 5% loss of yield was estimated to be approximately 1.8.

• Korean journal of applied entomology
• /
• v.53 no.2
• /
• pp.93-96
• /
• 2014

This study was conducted to determine the economic injury levels and control thresholds for the striped cabbage flea beetle, Phyllotreta striolata (Coleoptera: Chrysomelidae), on Chinese cabbage at two different planting times. The number of inoculated adults per 10 cabbages was 0, 2, 4, 8, and 16 at the early developmental stage of the cabbage5 days after planting) and 0, 10, 20, 30, and 40 at the middle developmental stage (30 days after planting). Damages to the leaves at the first inoculation were 2.5-21.1% and at the second inoculation were 1.8-26.3% after harvesting. The linear relationships between population density and yield reduction were as follows: Y = 1.3475X + 2.135 ($R^2$ = 0.8699) at the early developmental stage and Y = 0.703X - 1.78 ($R^2$ = 0.966) at the middle developmental stage. On the basis of these results, the economic injury levels caused 5% loss of yield; there were 2.1 adults per 10 Chinese cabbage at the early developmental stage and 9.6 adults per 10 Chinese cabbage at the middle developmental stage.

• Weed & Turfgrass Science
• /
• v.5 no.3
• /
• pp.165-169
• /
• 2016

To establish the soil management system for the efficient sod production, survey on the growth of zoysiagrass by different soil managements was conducted in repeated cultivation field with regard to soil physical properties. Soils were subjected to four types of management methods, which include (1) rolling (2) topdressing (3) topdressing + rolling (4) topdressing + tillage + rolling. The topdressing + tillage + rolling treatment significantly ameliorated soil physical properties such as bulk density, porosity and solid phase as compared to rolling and topdressing + rolling treatments, and was not significantly different from the topdressing treatment. Further growth and density of zoysiagrass except for the root dry weight in topdressing + tillage + rolling treatment were significantly higher than that only in rolling treatment. Topdressing + tillage + rolling treatment significantly increased the number of shoot as compared to the other treatments. Therefore, combined topdressing and tillage soil management practice should be conducted for the production of zoysiagrass in repeated cultivation field.

• Weed & Turfgrass Science
• /
• v.5 no.4
• /
• pp.260-267
• /
• 2016

Amino acids in the plant were intermediate metabolites which produced by uptake and assimilation of nitrogen and these extracts which gained by bio-chemical digestion from protein of plant or animal were a source of functional fertilizer. This study was conducted to evaluate effects of keratin amino acid fertilizer (KAF) gained from animal hair or hoof on changes of turfgrass quality and growth by investigating turf color index, chlorophyll index, shoot number, clipping yield, and nutrient content in the turfgrass tissue. Treatments were designed as follows; non-fertilizer (NF), compound fertilizer (CF), keratin amino acid fertilizer treatments [CF + KAF $0.26ml\;m^{-2}$ (CKF), CF + KAF $0.52ml\;m^{-2}$ (2CKF)], and only keratin amino acid fertilizer treatment (KF). Shoot number, clipping yield, and nitrogen uptake of KF were higher than those of CF. As compared with CF, soil chemical properties, turf color index, chlorophyll index and clipping yield of keratin amino acid fertilizer were not significant, but shoot number and uptake of N and K were increased significantly. These results show that the application of keratin amino acid fertilizer increased shoot number and growth by increased uptake of nitrogen and potassium.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.52-52
• /
• 2018

목초지에서 비점오염원 유출특성은 가축밀도(stocking rate)와 방목형태(grazing management practice)에 기인하여 다르게 나타난다. 전통적인 방목형태는 한 대상지역에서 높은 가축밀도의 연속적인 방목(continuous grazing)을 취하는 것인데, 이 경우 토양압밀에 따른 강우의 침투량 감소, 가축의 배설물 축적 등으로 비점오염 유출량이 증가할 수 있으며, 식물의 재성장기간 부족으로 지속적인 방목지 운영이 어려울 수 있다. 순환방목(rotational grazing)은 이러한 연속적 방목 형태의 부정적인 영향을 개선하고자 대안으로 제시되었다. 방법은 구역을 나누고 초본식물의 생육상태를 고려하여 일정기간이 지나면 다른 구역으로 이동 시키며 방목하는 형태이다. 기존의 연구들은 단위 면적당 적정 가축밀도, 필드규모에서 방목형태에 따른 비점오염 유출특성에 초점을 두고 있으며, 결과들은 가축밀도의 영향보다는 방목형태에 의한 수문, 수질 영향이 더 크다고 지적하고 있다. 이에 본 연구에서는 이러한 가축밀도(Heavy vs Light) 및 방목형태(Continuous vs Rotational)가 유역의 비점오염 유출특성에 미치는 영향을 정량적으로 평가하고자, 미국 북텍사스 지역에 위치한 Clear Creek 유역을 대상으로 4개의 방목시나리오(heavy continuous[HC], light continuous[LC], multi-paddock[MP], no grazing)를 구성하고 Soil and Water Assessment Tool(SWAT) 모형에 적용하였다. SWAT 모형은 대상유역 내 4개의 방목지에서 측정한 토양수분 및 식물 바이오매스 자료, 유역 출구점에서 관측된 장기간의 수문 수질 자료를 이용하여 검증되었다. 연구결과는 순환방목(MP) 시나리오가 수질보호 및 토양침식 방지, 식생의 영양염류 흡수능력이 커지는 것과 같이 생태계서비스 기능의 개선 측면에서 최적의 방목형태(best grazing management)인 것으로 나타났으며, 이러한 결과는 가축밀도 보다는 방목형태에 기인한 것으로 필드와 유역스케일에서 동일한 결과를 보여주었다. 그러나 유역 내 목초지의 차지비율에 따라 순환방목 채택에 따른 비점오염 유출량의 감소효과는 다르게 나타나게 된다.

• Korean journal of applied entomology
• /
• v.47 no.4
• /
• pp.473-478
• /
• 2008

Root-lesion nematode (Pratylenchus vulnus) and pin nematode (Paratylenchus sp.) were detected with high population density at the spray chrysanthemum greenhouse in Gumi, Gyeongbuk. The average density of P. vulnus and Paratylenchus sp. was 667 and 716 nematodes per 100 g soil and P. vulnus density were distributed 87% to the depth of $0{\sim}30$ cm in greenhouse. When spray chrysanthemum cv Chopin, was transplanted in September 2004 in greenhouse, P. vulnus were 854 nematodes/100 g soil in planting and increased 14,985 nematodes/100 g soils and 1g root after 10 weeks in harvest. Shoot weight and shoot height of spray chrysanthemum decreased 24.8% and 8.0% compared with non-infested P. vulnus after 10 weeks in greenhouse.

• Journal of Life Science
• /
• v.14 no.3
• /
• pp.490-495
• /
• 2004

Phosphate-solubilizing activities of the two strains (Burkholderia sp. DA23 and Klebsiella sp. DA7l-1) against tri-calcium phosphate and hydroxyapatite were quantitatively determined. Two strains were found to solubilize two types of insoluble phosphate different amounts of amino acid solutions in liquid culture. MPS ability of the strains was increased with concentration of amino acid addition. The optimal solubilization condition of insoluble phosphate in sucrose minimal medium were 0.1% amino acid solution, respectively. The efficiency of amino acid addition was no difference between the two types of insoluble phosphate, tri-calcium phosphate and hydroxyapatite.

• Ocean and Polar Research
• /
• v.24 no.4
• /
• pp.345-357
• /
• 2002

Ecological characteristics on habitats and morphological features of the seagrass Zostera caulescens Miki in Korea were examined. The biogeographical distribution of Z. caulescens was confirmed in the south coast of the Korea. Zostera caulescens usually inhabits at the inner bay, where is sheltered from wave action and 3.0 to 6.5 m deep. The sediment in habitats is composed of very fine muddy sand or sandy mud. In morphology, Z. caulescens is easily distinguished from other species of the genus by the formation of vegetative canopy on the top of reproductive stems. The number of longitudinal ribs in testa was 24 revealed by scanning electron microscope (SEM) while the number of ribs in Z. marina has been often reported to be 16-20. Purplish anthocyanin spots were displayed on the surface when the testa was removed. We found that the size and shape of leaf epidermal cells in Z. caulescens were very different from those of Z. marina when the leaf cuticles were removed by maceration which could be useful characters for identifying Zostera species. The leaf of Z. caulescens displays two different casts of color when the fresh plant is closely observed. The margins of leaves appear brighter than the center of leaves due to the thickening by the development of paralleled venation in the middle of leaves. The comparison of two populations of Z. caulescens in Korea showed that they were considerably different in their shoot density and biomass. The shoot density and biomass at Gabae population was $367.3 m^{-2}\;and\;725.7g$ dry wt $m^P{-2}$ respectively, while those at Jukrim population were $112.5m^{-2}\;and\;392.0g\;dry\;wt\;m^{-2}$, respectively.