• The Korean Journal of Ecology
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• 제21권5_3호
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• pp.703-712
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• 1998

Physicochemical factors, microbial population size and the properties of the bacterial isolates were estimated to find out the nature of soil ecosystem of Mt. Nam. Samples were obtained from the surface layer of soils on which specific plant community is developed. Average content of moisture and organic matter of the soils were 21.6% and 17.3%, respectively. These values were similar to those of developing forest soils, but were slightly lower than those of climax ecosystem such as Piagol in Mt. Chiri. Chiri. Content of phosphate was higher than those of other forest soils. The population size of soil bacteria ranged from 27.4 to 195.8 ${\times}\;10^5$ CFU/g. duy soil, and the size is somewhat dependent on the moisture and oranic matter content of soils. A large number of bacteria were able to decompose macromolecules such as starch, elastin and gelatin. Bacterial species composition of each soil was comparatively simple. Pseudomonas, Agrobacterium, Flavobacterium and Xanthomonas which are Gram-negative short rods were widely distributed in the forest soils. The endospore forming Bacillus species were also the main constituents of the soil microflroa. Actinomycetes were widely distributed in the forest soils, but the distribution pattern varied in each site. Most of the actinomycetes were also able to decompose organic macromolecules. The rate of resistant actinomycete strains to antibiotics and heavy metals were lower than those from cultivated soils, but higher than those from well-preserved forest soils. Antibiosis pattern of the actinomycete isolates was similiar to the resistance pattern. This means the forest soils of Mt. nam was somewhat interferred by artificial behabiour.

• Geomechanics and Engineering
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• 제8권2호
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• pp.173-186
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• 2015

The rapid urbanization in Pakistan is creating a shortage of sustainable construction sites with good soil conditions. Attempts have been made to use rice husk ash (RHA) in concrete industry of Pakistan, however, limited literature is available on its potential to improve local soils. This paper presents an experimental study on engineering properties of low and high plastic cohesive soils blended with 0-20% RHA by dry weight of soil. The decrease in plasticity index and shrinkage ratio indicates a reduction in swell potential of RHA treated cohesive soils which is beneficial for problems related to placing pavements and footings on such soils. It is also observed that the increased formation of pozzolanic products within the pore spaces of soil from physicochemical changes transforms RHA treated soils to a compact mass which decreases both total settlement and rate of settlement. A notable increase in friction angle with increase in RHA up to 16% was also observed in direct shear tests. It is concluded that RHA treatment is a cost-effective and sustainable alternate to deal with problematic local cohesive soils in agro-based developing countries like Pakistan.

• The Plant Pathology Journal
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• 제38권6호
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• pp.692-699
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• 2022

Bacterial wilt caused by Ralstonia solanacearum is considered one of the most harmful diseases of pepper plants. Recently, research on plant disease control through the rhizosphere microbiome has been actively conducted. In this study, the relationship with disease occurrence between the neighboring plant confirmed by analyzing the physicochemical properties of the rhizosphere soil and changes in the microbial community. The results confirmed that the microbial community changes significantly depending on the organic matters, P₂O₅, and clay in the soil. Despite significant differences in microbial communities according to soil composition, Actinobacteriota at the phylum level was higher in healthy plant rhizosphere (mean of relative abundance, D: 8.05 ± 1.13; H: 10.06 ± 1.59). These results suggest that Actinobacteriota may be associated with bacterial wilt disease. In this study, we present basic information for constructing of healthy soil in the future by presenting the major microbial groups that can suppress bacterial wilt.

• Journal of Ecology and Environment
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• 제44권2호
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• pp.62-71
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• 2020

Understanding vegetation structure and the relationship with environmental factors has been crucial for restoration and conservation of riparian zones. In this study, we conducted field survey in a riparian zone of Namhan River in South Korea both before and after flooding in order to understand temporal and spatial variations of riparian vegetation. There were significant temporal and spatial variations in species composition, and distribution patterns of vegetation were different along a gradient of elevation above the water level. At low elevation, Zizania latifolia was dominant throughout the field survey periods, and Bidens frondosa began to grow late and dominated both in post-flooding 1 and 2. Prior to flooding, Scirpus radicans and Polygonum thunbergii were widely distributed at middle elevation, while Artemisia vulgaris, Phragmites australis, and Miscanthus sacchariflorus were dominant at high elevation. After flooding, P. thunbergii was dominant at middle elevation with most other species decreasing, and more invasive or pioneer plants, including Artemisia princeps, H. scandens, and Sicyos angulatus, were observed at high elevation. Species composition and distribution patterns were homogeneous at low elevation, whereas dynamic variations of vegetation were observed both temporally and spatially at higher elevations. Elevation and distance from the water front were the most principal factors governing vegetation structure. Furthermore, soil physicochemical properties were also found to determine species composition and distribution patterns. These results indicate that vegetation structure in the riparian zones is formed by the combined effects of hydrological regime and soil physicochemical properties, inherent characteristics of species, and interspecific competition. Understanding of temporal and spatial variations of riparian vegetation may provide useful insights into ecological restoration and conservation of the vegetation within the riparian zones.

• Journal of Ecology and Environment
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• 제43권2호
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• pp.129-160
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• 2019

Background: Characterizing and describing soils and land use and make a suggestion for sustainable utilization of land resources in the Ethiopian Rift valley flat plain areas of Lake Chamo Sub-Basin (CSB) are essential. Objectives: To (1) characterize soils of experimental area according to World Reference Base Legend and assess the nature and extent of salinity problems; (2) characterize land use systems and their role in soil properties; and (3) identify best land use practices used for both environmental management and improve agricultural productivity. Methods: Twelve randomly collected soil samples were prepared from the above land uses into 120 composites and analyzed. Results: Organic carbon (OC) and total nitrogen (TN) were varied along different land uses and depleted from the surface soils. The soil units include Chernozems (41.67%), Kastanozems (25%), Solonchaks (16.67%), and Cambisols (16.67%). The identified land uses are annual crops (AA), perennial crops (PA), and natural forest (NF). Generally, organic carbon, total nitrogen, percentage base saturation (PBS), exchangeable (potassium, calcium, and magnesium), available phosphorus (P₂O₅), manganese, copper, and iron contents were decreased in cultivated soils. Soil salinity problem was observed in annuals. Annuals have less nutrient content compared to perennials in irrigated agriculture while it is greater in annuals under rainfed. Clay, total nitrogen, available phosphorus, and available potassium (K₂O) contents were correlated positively and highly significantly with organic carbon and electrical conductivity. Conclusion: Management practices that improve soil quality should be integrated with leguminous crops when the land is used for annual crops production.

• 한국토양비료학회지
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• 제47권6호
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• pp.418-424
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• 2014

The Agricultural Land Remodeling Project was launched for agricultural fields with potential risk of flooding which were placed in low-lying area as a part of agricultural sectors of the National 4 River Project. It induced of the reclaimed agricultural fields on a national scale. The arable lands reestablished by reclamation have caused several big problems such as destruction of soil physicochemical properties, and thus the techniques to solve disadvantages were urgently required. In this study, we collected experimental samples from top soils in three agricultural areas, one from conventional agricultural fields (Hwasun, Jeollanam-do) and the others from reclaimed (remodelled) agricultural fields (Naju, Jeollanam-do and Gumi, Gyeongsangbuk-do), The soil chemistry data were analyzed using statistic tools such as semi-variance and kriging, and differences between natural and reconstructed soils were examined. The score, R (Ao) which indicates a dependence distance between each chemical element, was as follows; 21.8~43.5 (Conventional, Hwasoon), 4.4~70.6 (Remodelled, Naju) and 5.3~43.6 (Remodelled, Gumi). These results suggested that chemical properties of the reclaimed agricultural fields had a huge variation. Moreover, the result of kiriging maps also represented a ununiform pattern in the reclaimed lands. As a result of this study, it is strongly required to build up the soil type-specific management techniques for the reclaimed agricultural lands.

• Weed & Turfgrass Science
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• 제3권2호
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• pp.143-149
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• 2014

본 연구는 아메리카동애등에분변토(soldier fly casts; SFC)의 단점을 개량하기 위해 코코피트(cocopeat; Coco)와 혼합된 토양개량제의 골프장 토양개량제로서의 사용가능성을 평가하기 위해 모래와 혼합비율 별 물리화학성을 조사하였다. 토양개량제는 SFC, Coco, 25% SFC+75% Coco(Mix1), 50% SFC+50% Coco (Mix2) 및 75% SFC+25% Coco (Mix3)이었고, 각각 3%, 5%, 7% 및 10% 씩 혼합되어 모래상토를 조성하였다. SFC, Mix1, Mix2 및 Mix3는 토양 pH와 EC에서 고도의 상관성(P<0.01)을 나타내어 토양개량제의 혼합에 의해 모래상토의 토양화학성에 영향을 주었다. SFC, Coco, Mix1, Mix2 및 Mix3은 모세관공극, 비모세관공극 및 공극이 USGA기준에 적합하였고, 혼합비율이 증가할수록 모세관공극과 총공극이 증가하였으며(P<0.05), Mix1과 Mix3의 비모세관공극은 모세관공극과 수리전도도에서 부의 상관성을 보였다(P<0.01). Mix1, Mix2 및 Mix3에서 SFC는 상토의 모세관공극의 변화에 영향을 주었고, Coco는 모세관공극과 총공극의 변화에 영향을 주었다. 이들 결과를 종합할 때, SFC와 Coco가 혼합된 토양개량제(Mix1~3)는 SFC보다 모래상토의 모세관 공극과 수리전도도를 개선하여 SFC의 단점을 보완한 것으로 평가되었다.

• 한국환경과학회지
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• 제23권6호
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• pp.995-1001
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• 2014

When relations improve between North and South Korea, there will be demand for North Korean edible plants because of the low labor cost and similar environmental conditions. However, there is no reliable information about trace elements, metals, and metalloids in edible plants from North Korea. Selenium (Se) and germanium (Ge) have positive effects on basic human health and are therapeutical in diverse illnesses. Metal and metalloid (Cd, Pb) poisoning, on the other hand, can cause many health problems. Plants collected from North Korea had higher selenium content than those from South Korea. Although none of the collected species exceeded the permissible levels of cadmium and lead, their content in plants was significantly higher in North Korea than in South Korea. The high metal contents in plants collected from North Korea may be associated with the soil physicochemical properties as well as the accumulated amounts of elements in the soil.

• 환경위생공학
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• 제11권3호
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• pp.69-77
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• 1996

The result of isolated and selected to the strain having the emulsifying activity from soil's strain the strain was identified as Candida genus. The strain was investigated with culture condition at pH culture temperature, flow rate of air, strring rate etc., and physicochemical properties of the biosurfactant were examined. The optimum composition of medium for a strain cultivation were obtained as follow : glucose ; 100g/L, yeast extract ; 10g/L, urea ; 1.0g/L, KH$_{2}$PO$_{4}$ ; 50mg/L, MgSO$_{4}$ ; 500mg/L, and the op condition of cultivation was as follow : pH ; 3.0, temperatlue ; 24$\circ $C, strring rate ; 40rpm. The maximum yield of biosurfactant was obtained by pH ; 3.0-3.5, and temperature ; 25$\circ $C. The degree of emulsification of syntesized biosurfactant was increased clearly by increasing concentration of biosurfactant and it's stability was maintained for a long time. The surface tension of biosurfactant was varied with pH, especially it was showed that the surface tension was high at acidic pH.

• 환경영향평가
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• 제21권1호
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• pp.81-91
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• 2012

In this study, it is grasped the status of nutrients through an investigation of release characteristics and physicochemical properties of sediments on reservoir. And then the effect of sediments is evaluated on the water quality in reservoir. In the results of physicochemical analysis, the pollution level of midstream is the highest, which shows the traits that the water is more deeper and takes place a deposition consistently. Then, the pollution level of upstream is higher than downstream's because inflow has influence on the upstream directly. The downstream is located near tidal gate so that the soil particles can be moved easily and are difficult to be deposited due to the distribution of seawater by control of tidal gate. Therefore, the downstream is showed the lowest pollution level than the others. Also, the concentration of SOD(Sediment Oxygen Demand) in the upstream which is influenced on the effect of inflow is highest than the others. When it analyzes under anaerobic and aerobic condition to understand the release characteristic of sediment, it shows that the release rate is low or negative under the aerobic condition. Whereas the release rate is usually positive under the unaerobic condition relatively. According to these results, it is necessary to maintain the proper environmental factors of water body for decreasing the release rate of sediment. Because the release rate is changeable under the different condition of water body. Therefore, proper strategies are required for increasing the self-purification of water as well as keeping the aerobic condition of sediment and managing a sediment layer directly to control the inner-pollution by the sediment of reservoir.