• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1537-1543
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• 2008

We tested Trichoderma harzianum as a biocontrol agent for Rhizoctonia solani AG2-1, using six natural antifungal materials to improve its efficacy. Among the six materials tested, peony (Paeonia suffruticosa) root bark (PRB) showed the strongest antifungal activity against R. solani AG2-1, and was not antagonistic to T. harzianum. Scanning electron microscopy showed that treatment with PRB extract resulted in shortened and deformed R. so/ani AG2-1 hyphal cells. The control of radish damping-off caused by R. so/ani AG2-1 was greatly increased by combined treatments of T. harzianum and PRB, as compared with either of the two treatments alone, with the control effect increased from 42.3-51.5% to 71.4-87.6%. The antifungal compound in PRB, which was isolated in chloroform and identified as paeonol by mass spectrometry, $^1H$ NMR, and $^{13}C$ NMR analyses, inhibited the growth of R. so/ani AG2-1 but not that of T. harzianum. Thus, PRB powder or extract may be used as a safe additive to T. harzianum to improve the control of the soil borne diseases caused by R. so/ani AG2-1.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.4
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• pp.80-96
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• 1992

This study was carried out in order to determin optimum irrigation requirements and water management practices for normal growth of dry field crops in reclaimed tidelands, and apply m planning of the irrigation projects. Desalinization experiments were performed by water management practices in the experimental field with high salt concentration, and growth experiments were conducted by irrigation point treatments using tomato and beet with relatively high salt tolerance. The results obtained from this study were summarized as follows : 1. Leaching or rinsing-leaching method was found to be effective in desalinizing the reclaimed tideland with rather high permeability. In this case, the water requirement for desalinizing the root zone layer of 40cm in depth, was estimated to be 1,200mm in depth. 2.The gypsum treatment in the desalinization of reclaimed tidelands, was ineffective in water requirements ; however, it could produce the desired effect in the facility of desalinization and the shortening of desalinization period with the sustaining permeability, in case of the desalinization by leaching method. 3.The optimum irrigation point which maintains the salt concentration within salt tolerance and maximizes the crop yield in reclaimed tidelands of silt loam soil, was found to be pF 1.6 in tomato and pF 1.8 in beet. The interval of irrigation date within 2 days was proved to he effective in both cases. 4.The optimum irrigation requirement and the water reguirement for the prevention of salt rise during the growing period after transplanting, were estimated to be 602mm(6.7mm/day) and 232mm for tomato, respectively. 5.The optimum irrigation requirement and the water requirement for the prevention of salt rise during the growing period after transplanting, were estimated to be 261mm(3.7mm/day) and 66mm for beet, respectively.

• The Korean Journal of Ecology
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• v.15 no.2
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• pp.137-145
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• 1992

When exposed to 1, 700 ml of 0.089, 0.445 or 0.890 mM/l cadmius solution, dock (rumex crispus L)plants from heavily polluted chungrangchon site absorbed 0.0404, 0.2244 or 0.4929 mM of cadmium per g dw during the first 4 hours, which were 5.0~30.8 times faster uptake rate than those of water hyacinth (eichhornia crassipes Solm. - laub). Zinc, with which cadmium generally occurs together, did not affect the uptake rate in the concentration range of 0.0306 ~0.0918 mM/l. rumex cripus from chungrangchon site and from less polluted shingalchon site, when exposed to 1, 700 ml of 0.089 mM/l solution for 3 days, removed 68.4% and 63.2%, repectively, of the cadmium initially present in the solution. And when exposed to cadmium solution of the same concentration for the second time after cadmium-free hydroponic culture for three days, these plants removed 76.1% and 66.8% of cadmium, respectively. These removal rates were not significantly different between collection sites or between exposures, but were about 2 times greater for the first exposure, and 2~5 times greater for the second exposure, than those of water hyacinth. these results incate that rumex cripus can absorb, and thus remove, large amount of cadmium ion in wastewater, and so can be used in wastewater treatment, e.g. soil trench method. since there was large difference among the plants in the ability to absorb cadmium, it should be possible to select for strain with greater ability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.207-217
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• 1992

In this study, isolated and cultured nitrogen fixed microbes were seeded in the three-phase fluidized bed in which gas, solid and liquid were contacted directly. Input velocity was varied from 8.12 cm/hr to 16.32 cm/hr. And upflow gas pressure was fixed to 80 psi. Return ratios were from 0.2 to 0.6 with the each experimental condition. According to these condition, movement of media, growth of biofilm and removal efficiency were measured. As the results, in case of briquette ash, biofilm was developed to $170{\mu}m$ when velocity was 8.12 cm/hr and return ratio was 0.6. In this condition, COD removal efficiency was 97% and $NH_4$-N removal efficiency was 83%. At the same condition, biofilm thickness of glass bead was $17.59{\mu}m$ and its COD and $NH_4$-N removal efficiency was 83% and 72%. Nitrogen fixed microbes have following characters: it formed dark-brownish sludge, excellent adhesive force, easy solid-liquid separation and low oxygen uptake ratio, but sensitive to DO concentration. Not only it endured shock loading, but required short time to steady state.

• Journal of Plant Biotechnology
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• v.31 no.1
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• pp.67-72
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• 2004

An efficient protocol has been developed for rapid mass propagation of sweetpotato from shoot-tips derived embryogenic callus. Optimal embryogenic callus was induced from shoot apical meristem explants on Murashige and Skoog (MS) medium supplemented with 1mg/L 2,4-D. The addition of casein hydrolysate in the media increased the embryogenesis efficiency of sweetpotato. Somatic embryos were easily induced from the embryogenic callus on MS basal medium containing 300-500mg/L casein hydrolysate without phytohormon. Treatment of casein hydrolysate (100∼300mg/L) with 1mg/L 2,4-D also improved the secondary embryonic efficiency from somatic embryos below 2mm in length. Plant regeneration was achieved via somatic embryogenesis and direct organogenesis. Regenerated planlets with well developed shoots and roots on MS basal medium were successfully transferred to soil.

• Korean Journal Plant Pathology
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• v.2 no.2
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• pp.114-120
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• 1986

Significant reduction in disease severity of bacterial wilt (Pseudomonas solanacearum) on the susceptible tobacco cultivar BY 4 was observed until mid-July in a naturally infested field when bacterial suspensions of avirulent isolate were applied to tobacco root zones at one day before and fourty days after transplanting into the field. However, rapid increase in disease severity after mid-July resulted in the same severity $(70\%)$ as on cultivar BY 4 without the application of the avirulent bacterial suspension at the end of the season. Yield increase in cultivar BY 4 was $35\%$ due to the treatment, resulting in $10\%$ price increase. The suppression me chanism did not appear to be dependent upon the inhibition of the virulent bacterial multiplication by the avirulent bacteria in tobacco rhizosphere soil because of no significant difference in the density of the patho genic bacteria between treated and untreated plant root zones. However. penetration of the virulent bacteria into the root systems and their multiplication in tobacco stem were inhibited remarkably by preinoculation with avirulent one, suggesting that those are related to the suppression of disease incidence.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.2
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• pp.59-65
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• 2000

The vertical distribution of pore water pressure in the highly saturated sand layer under the oscillating water pressure is studied theoretically and experimentally. By the experiments it is shown that the water pressure acting on the sand surface propagates into the sand layer with the damping in amplitude and the lag in phase, and that the liquefaction, the state that the effective stress becomes zero, occurs under certain conditions. These experimental results are explained fairly well by the same theoretical treatment as for the ground water problems in the elastic aquifer. The main characteristics of liquefaction clarified by the analysis are as follows: 1) The depth of the liquified layer increases with the increase of the amplitude and the frequency of the oscillating water pressure. 2) The increase of the volume of the water and the air in the layer increases the liquified depth. Especially the very small amount of the air affects the liquefaction significantly. 3) The liquified depth decrease rapidly with the increase of the compressibility coefficient of the sand. 4) In the range beyond a certain value of the permeability coefficient the liquified depth decrease with the increase of the coefficient.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.1
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• pp.16-20
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• 2005

Consolidation of dredged fill has become important task for site treatment. The variation of stratum thickness during consolidation processing needs to be taken into consideration since hydraulic fill would go through a much larger scale strain than land soil when it is subject to a load. In this study, the consolidation period considering the variation of stratum thickness was analyzed and compared the results with those of existing consolidation studies which did not consider the variation of stratum thickness. According to the results of the study, the consolidation period of the ground with a larger strain was calculated more close to observed value in case of Mikasa theory which takes the variation of stratum thickness into consideration.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.3
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• pp.147-151
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• 2003

Normal seed tubers and plug seedlings raised from stem cutting and mini-tubers ($10\pm3$ g) were planted or transplanted on August 20,2001 in bare soil or under transparent and black polyethylene film mulches to evaluate the effects of mulch material and seedling type on the growth and tuber yield of fall-grown potato (Solanum tuberosum L. cv. Dejima) in Jeju region. Total tuber number per plant was 4.6 regardless of mulch treatment, and direct planting seed potatoes resulted in the greatest tubers (5.14)/plant and followed by transplanting seedlings raised from cutting and mini-tubers (4.15 and 5.15 tubers/plant). Transparent and black polyethylene film mulches increased total tuber yield by 16 and 8%, respectively, and average tuber weight by 14 and 12%, respectively, compared with no mulch (21.16 t/ha and 72.2 g/tuber). Transplanting plug seedlings raised from cutting resulted in the greatest tuber yield, followed by transplanting plug seedlings raised from mini-tubers and direct planting seed potatoes.

• Microbiology and Biotechnology Letters
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• v.17 no.5
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• pp.440-446
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• 1989

Penicillium sp. CB-20 was selected for its strong polygalacturonase activity among various strains of molds found in soil. It was found that the production of polygalacturonase reached to maximum when on the wheat bran medium containing pectin as carbon source, the strain was cultured for 60 hours at 3$0^{\circ}C$. The enzyme was purified to 29.21 food by ammonium sulfate treatment, Sephadex G-25, G-15, G-150 gel filtration, DEAE-cellulose and DEAE-Sephadex A-50 ion-exchange chromatography. Yield of the enzyme purification was 2.31 %. When the purified enzyme was applied to sodium dodecyl sulfate polyacrylamide gel electrophoresis, the molecular weight was estimated 21, 000. The amino acid composition indicated relatively high contents of gultamic acid, glycine and histidine.