• Title/Summary/Keyword: Soil condition

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Modeling the effects of excess water on soybean growth in converted paddy field in Japan 1. Predicting groundwater level and soil moisture condition - The case of Biwa lake reclamation area

  • Kato, Chihiro;Nakano, Satoshi;Endo, Akira;Sasaki, Choichi;Shiraiwa, Tatsuhiko
    • Proceedings of the Korean Society of Crop Science Conference
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    • 2017.06a
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    • pp.315-315
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    • 2017
  • In Japan, more than 80 % of soybean growing area is converted fields and excess water is one of the major problems in soybean production. For example, recent study (Yoshifuji et al., 2016) suggested that in the fields of shallow groundwater level (GWL) (< 1m depth), rising GWL even in a short period (e.g. 1 day) causes inhibition of soybean growth. Thus it becomes more and more important to predict GWL and soil moisture in detail. In addition to conventional surface drainage and underdrain, FOEAS (Farm Oriented Enhancing Aquatic System), which is expected to control GWL in fields adequately, has been developed recently. In this study we attempted to predict GWL and soil moisture condition at the converted field with FOEAS in Biwa lake reclamation area, Shiga prefecture, near the center of the main island of Japan. Two dimensional HYDRUS model (Simuinek et al., 1999) based on common Richards' equation, was used for the calculation of soil water movement. The calculation domain was considered to be 10 and 5 meter in horizontal and vertical direction, respectively, with two layers, i.e. 20cm-thick of plowed layer and underlying subsoil layer. The center of main underdrain (10 cm in diameter) was assumed to be 5 meter from the both ends of the domain and 10-60cm depth from the surface in accordance with the field experiment. The hydraulic parameters of the soil was estimated with the digital soil map in "Soil information web viewer" and Agricultural soil-profile physical properties database, Japan (SolphyJ) (Kato and Nishimura, 2016). Hourly rainfall depth and daily potential evapo-transpiration rate data were given as the upper boundary condition (B.C.). For the bottom B.C., constant upward flux, which meant the inflow flux to the field from outside, was given. Seepage face condition was employed for the surrounding of the underdrain. Initial condition was employed as GWL=60cm. Then we compared the simulated and observed results of volumetric water content at depth of 15cm and GWL. While the model described the variation of GWL well, it tended to overestimate the soil moisture through the growing period. Judging from the field condition, and observed data of soil moisture and GWL, consideration of soil structure (e.g. cracks and clods) in determination of soil hydraulic parameters at the plowed layer may improve the simulation results of soil moisture.

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Prediction of Soil Deformation with Nonlinear-Anisotropic Model (비선형 이방성 모델을 이용한 흙의 변형 거동 예측)

  • 윤충구;정영훈;정충기
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.03a
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    • pp.41-48
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    • 2002
  • The fact that nonlinearity and anisotropy of soil should be considered for the proper estimation of soil deformation has been recongnized for a long time. In this study, a new stiffness model which can reflect both nonlinearity and anisotropy is proposed. Nonlinearity is simulated by Ramberg-Osgood model and anisotropy is modeled with the cross-anisotropic elasticity. Analysis results with the developed model compared with those from analyses using linear isotropic model, linear anisotropic model, and nonlinear isotropic model. In the triaxial compression like condition, the effects of nonlinearity on the vertical strain are significant, but soil anisotropy does not affect the vertical strain. In 1-dimensional deformation condition, however, both nonlinearity and anisotropy of soil influence the final magnitude of the vertical strain. Also the increase of poisson's ratio magnifies the effect of anisotropy on the vertical strain in this condition.

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An analysis of runoff characteristic by using soil moisture in Sulma basin (설마천 연구지역에서의 토양수분량을 활용한 유출 발생 특성분석)

  • Kim, Kiyoung;Lee, Yongjun;Jung, Sungwon;Lee, Yeongil
    • Journal of Korea Water Resources Association
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    • v.52 no.9
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    • pp.615-626
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    • 2019
  • Soil moisture and runoff have very close relationship. Especially the water retention capacity and drainage characteristics of the soil are determined by various factors of the soil. In this study, a total of 40 rainfall events were identified from the entire rainfall events of Sulma basin in 2016 and 2017. For each selected events, the constant-K method was used to separate direct runoff and baseflow from total flow and calculate the runoff coefficient which shows positive exponential curve with Antecedent Soil Moisture (ASM). In addition to that, the threshold of soil moisture was determined at the point where the runoff coefficient starts increasing dramatically. The threshold of soil moisture shows great correlation with runoff and depth to water table. It was founded that not only ASM but also various factors, such as Initial Soil Moisture (ISM), storage capacity of soil and precipitation, affect the results of runoff response. Furthermore, wet condition and dry condition are separated by ASM threshold and the start and peak response are analyzed. And the results show that the response under wet condition occurred more quickly than that of dry condition. In most events occurred in dry condition, factors reached peak in order of soil moisture, depth to water table and runoff. However, in wet condition, they reached peak in order of depth to water table, runoff and soil moisture. These results will help identify the interaction among factors which affect the runoff, and it will help establish the relationship between various soil conditions and runoff.

Effect on the Growth Condition of Chionanthus retusa, Roadside Tree in Cheongyechon (청계천 이팝나무 가로수 생육환경이 성장에 미치는 영향)

  • Yoon, Sowon
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.11 no.3
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    • pp.129-138
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    • 2008
  • This study was carried out to examine the growth condition of Chionanthus retusa, roadside tree in Cheongyechon (CGC) and to investigate the relationship soil characteristics and tree vitality and chlorophyll contents of it. Growth condition of tree (condition of flower, leaves and branch, % of flowering, height, diameter at breast height, width, vitality and chlorophyll contents) and physiochemical relation item (pH, organic matter, K, Mg, Na, Ca, P) were investigated. The result are as follows : 1. The growth condition of flower, leaves and branch in the left side of CGC is better than the right side since the quantity of sunshine of left side of CGC is much more than the right side. 2. The average pH was alkaline. P and organic contents were much lower than the standards. 3. Tree vitality and chlorophyll contents were bad where were high user density and high buildings, such as 1, 2 area near Jong-gak and jongro 3 ga. Among the physiochemical factors of soil which affect tree vitality, K and P were found to be the main factors. Therefore, in order to improve the growth environment of roadside tree in CGC, it is needed to do periodical soil fertilizing and improve physical characteristics of soil such as, permeability and porosity by soil conditioner.

Responses of Lactuca Sativa (Lettuce) to Fertilization Rates at Various Soil Moisture Conditions at Protected Cultivation

  • Jung, Kang-Ho;Sonn, Yeon-Kyu;Han, Kyoung-Hwa;Zhang, Yong-Seon
    • Korean Journal of Soil Science and Fertilizer
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    • v.48 no.1
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    • pp.50-56
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    • 2015
  • This research was performed to test the hypothesis that the optimal fertilization rate for lettuce is various with soil moisture conditions. The experiment was conducted under a rainfall-intercepted facility in Suwon, South Korea from 2002 to 2003. Soil was irrigated at 30, 50, or 80 kPa of soil moisture tension at 15 cm soil depth in 2002 spring and fall and 20, 30, 50, or 80 kPa in 2003 spring. Fertilization was performed with four levels in spring for both years: none, 0.5, 1.0, and 1.5 times of the recommended N, P, and K fertilization rate. The irrigation amount increased with decreased irrigation starting point as soil moisture tension. The maximum yield was found at the lowest soil moisture tension in spring while irrigation at 50 kPa resulted in the greatest yield in fall. The yield responses of lettuce to fertilization rates were various with soil moisture condition. In spring, maximum yield was found at 1.0 or 1.5 times of the recommended fertilization rate at 20, 30, and 50 kPa irrigation while 0.5 or 1.0 times of fertilization rate resulted in the maximum yield in fall. Especially for 80 kPa irrigation in 2003 spring, yield was decreased by fertilization. It suggested that the optimum fertilization rate for lettuce is affected by soil moisture condition and that lower fertilization rate should be suggested when soil is managed in drier condition.

A hysteresis model for soil-water characteristic curve based on dynamic contact angle theory

  • Liu, Yan;Li, Xu
    • Geomechanics and Engineering
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    • v.28 no.2
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    • pp.107-116
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    • 2022
  • The steady state of unsaturated soil takes a long time to achieve. The soil seepage behaviours and hydraulic properties depend highly on the wetting/drying rate. It is observed that the soil-water characteristic curve (SWCC) is dependent on the wetting/drying rate, which is known as the dynamic effect. The dynamic effect apparently influences the scanning curves and will substantially affect the seepage behavior. However, the previous models commonly ignore the dynamic effect and cannot quantitatively describe the hysteresis scanning loops under dynamic conditions. In this study, a dynamic hysteresis model for SWCC is proposed considering the dynamic change of contact angle and the moving of the contact line. The drying contact angle under dynamic condition is smaller than that under static condition, while the wetting contact angle under dynamic condition is larger than that under static condition. The dynamic contact angle is expressed as a function of the saturation rate according to the Laplace equation. The model is given by a differential equation, in which the slope of the scanning curve is related to the slope of the boundary curve by means of contact angle. Empirical models can simulate the boundary curves. Given the two boundary curves, the scanning curve can be well predicted. In this model, only two parameters are introduced to describe the dynamic effect. They can be easily obtained from the experiment, which facilitates the calibration of the model. The proposed model is verified by the experimental data recorded in the literature and is proved to be more convenient and effective.

Predicting Surface Runoff and Soil Erosion from an Unpaved Forest Road Using Rainfall Simulation (인공강우실험에 의한 임도노면의 지표유출량 및 토양유실량 평가)

  • Eu, Song;Li, Qiwen;Lee, Eun Jai;Im, Sangjun
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.18 no.3
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    • pp.13-22
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    • 2015
  • Unpaved forest roads are common accessways in mountain areas being used for forestry purposes. The presence of forest roads produces large volumes of surface runoff and sediment yield due to changes in soil properties and hillslope profile. Rainfall simulation experiments were conducted to estimate the impacts of above-ground vegetation and antecedent soil water condition on hydrology and sediment processes. A total of 9 small plots($1m{\times}0.5m$) were installed to represent different road surface conditions: no-vegetation(3 plots), vegetated surface(3 plots), and cleared vegetation surface(3 plots). Experiments were carried out on dry, wet, and very wet soil moisture conditions for each plot. Above ground parts of vegetation on road surface influenced significantly on surface runoff. Runoff from no-vegetation roads(39.24L) was greater than that from vegetated(25.05L), while cleared-vegetation condition is similar to no-vegetation roads(39.72L). Runoff rate responded in a similar way to runoff volume. Soil erosion was also controlled by land cover, but the magnitude is little than that of surface runoff. Even though slight differences among antecedent soil moisture conditions were found on both runoff and soil erosion, runoff rate and soil losses were increased in very wet condition, followed by wet condition. The experiments suggest that vegetation cover on forest road surface seems most effective way to reduce surface runoff and soil erosion during storm periods.

Nitrogen Fertilizer Management for Improving Rice Quality under Different Salinity Conditions in Tidal Reclaimed Area (미질향상을 위한 간척지 토양 염농도별 적정 질소시비량)

  • 최원영;이규성;고종철;박홍규;김상수;김보경;김정곤
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.49 no.3
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    • pp.194-198
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    • 2004
  • This study was conducted to identify the appropriate nitrogen fertilizer application rate for improving rice quality in tidal reclaimed area, at the Gyehwado substation of the Honam Agricultural Research Institute during 2002-2(103. The experimental fields contained 0.1% (low salinity) and 0.3-0.4% (medium salinity) Nacl in soil solution. Plant height at panicle formation stage was tall ay heavy nitrogen level and the effect of heavy nitrogen was higher in low than in high soil salinity condition. Heading date was not affected by applied nitrogen levels from 8 to 16 kg/10a in low soil salinity condition but it was one day later in 24 kg/10a nitrogen level when compared with the standard nitrogen level,20 kg/10a. In middle soil salinity condition, the heading date was one day earlier in 8 to 16 kg/10a and similar in 24 kg/10a, when compared with 20 kg/10a nitrogen level. And also it was four days later in middle than in low soil salinity condition. In low soil salinity condition, grain number $\textrm{m}^2$ increased but ripened grain ratio decreased as the nitrogen application increased and finally, milled rice yield was not different among heavy nitrogen application levels compared with 12 kg/10a. Head rice ratio was high and protein content was low in 12 kg/10a or lower nitrogen level. In middle soil salinity condition, grain number $\textrm{m}^2$ increased and ripened grain ratio was not affected as the nitrogen application increased. And finally, milled rice yield increased with increasing nitrogen application levels, Head rice ratio was high and protein content was not affected by nitrogen application levels. Therefore, on the basis of milled rice yield and rice grain quality inreclaimed land, the appropriate nitrogen application level would be 12 kg/10a in low soil salinity condition and 20 kg/10a in middle soil salinity condition.

Study on the Natural Frequency of Wind Turbine Tower Based on Soil Pile interaction to Evaluate Resonant Avoidance Frequency (지반조건 상호작용을 고려한 풍력발전타워의 공진회피 진동수 산정을 위한 고유진동수 해석 연구)

  • Kim, Pyoung-Hwa;Kang, Sung-Yong;Lee, Yun-Woo;Kang, Young-jong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.4
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    • pp.734-742
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    • 2016
  • Global warming and the depletion of fossil fuels have been caused by decades of reckless development. Wind energy is one form of renewable energy and is considered a future energy source. The wind tower is designed with a fundamental frequency in the soft-stiff design between the 1P and 3P range to avoid resonance. Usually, to perform natural frequency analysis of a wind tower, the boundary condition is set to the Fixed-End, and soil-pile interaction is not considered. In this study, consideration of the effect of soil-pile interaction on the wind tower was included and the difference in the natural frequency was studied. The fixed boundary condition was not affected by the soil condition and depth of the pile and the coupled spring boundary condition was unaffected by the depth of pile but affected by the depth of the pile, and the Winkler spring boundary condition is affected by both the soil condition and the depth of the pile. Therefore, the coupled spring boundary condition should be used in shallow depth soil conditions because the soil condition does not take the shallow depth soil into consideration.

Evaluation of the Impact of Land Surface Condition Changes on Soil Moisture Field Evolution (지표면 조건의 변화에 따른 토양수분의 변화 평가)

  • Yu, Cheol-Sang
    • Journal of Korea Water Resources Association
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    • v.31 no.6
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    • pp.795-806
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    • 1998
  • Soil moisture is affected by regional climate, soil characteristics and land surface condition, etc,. Especially, the changes in land surface condition is more than other factors, which is mainly due to rapid urbanization and industrialization. This study is to evaluate how the change of land surface condition impacts on soil moisture field evolution using a simple model of soil moisture dynamics. For the quantification of soil moisture field, the first half of the paper is spared for the statistical characterization based on the first- and second-order statistics of Washita '92 and Monsoon '90 data. The second half is for evaluating the impact of land cover changes through simulation study using a model for soil moisture dynamics. The model parameters, the loss rate and the diffusion coefficient, have been estimated using the observed data statistics, where the changes of surface conditions are considered into the model by applying various parameter sets with different second-order statistics. This study is concentrated on evaluating the impact due to the changes of land surface condition variability. It is because we could easily quantify the impact of the changes of its areal mean based on the linear reservoir concept. As a result of the study, we found; (1)as the variability of land surface condition, increases, the soil moisture field dries up more easily, (2)as the variabilit y of the soil moisture field is the highest at the beginning of rainfall and decreases as time goes on to show the variability of land surface condition, (3)the diffusion effect due to surface runoff or water flow through the top soil layer is limited to a period of surface runoff and its overall impact is small compared to that of the loss rate field.

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