Journal of the Japanese Society of Soil Physics
Online ISSN : 2435-2497
Print ISSN : 0387-6012
Volume 89
Showing 1-7 articles out of 7 articles from the selected issue
  • [in Japanese]
    2002 Volume 89 Pages 1-
    Published: 2002
    Released: October 19, 2021
    JOURNAL FREE ACCESS
    Download PDF (323K)
  • Velu Rasiah, Tahei Yamamoto
    2002 Volume 89 Pages 3-13
    Published: 2002
    Released: October 19, 2021
    JOURNAL FREE ACCESS
    Physical and mechanical stresses induced changes in clay dispersion is a major sustainability and environmental issue, particularly in large-scale intensive agricultural production systems. However, the dispersed clay may re-stabilize when the stresses are reduced or minimized/ removed. The objectives of this study are to (i) quantify the maximum potentially dispersible (DCmax) and stabilizable clay (SCmax) in soils with textural differences when the stresses were introduced and reduced, respectively, and (ii) identify the role of inherent soil variable(s) on DCmax and SCmax- Dispersible clay measurements were conducted at monthly intervals for 3 years on seven soil types under different cropping treatments. The cropping treatments used in this study were conventionally tilled continuous corn (CTCC) and forages, which were established in 1989 on plot that were previously under CTCC for more than 10 years. The CTCC represents stress imposed and the forages the stress reduced system. The DCmax in the stress imposed system across soils ranged from 3.2 to 16.6 % compared to 6.4 to 33.8 %, the total clay (TC) content. The DCmax increased with increasing TC and decreasing soil organic matter (SOM) content. The SCmax in the stress reduced system across soils ranged from 1.2 to 4.5 % and it increased with increasing TC and SOM. Eleven to 37 % of the DCmax was re-stabilized during the 3-year period under forages, i.e. stress reduced system. The amount of SOM in the soil at the time of switchover from CTCC played a significant role in the re-stabilization of dispersed clay, particularly in soils with similar TC. The results show the stabilization of dispersed clay under reduced stresses depended on DCmax and SOM.
    Download PDF (616K)
  • Yukiyoshi Iwata, Hajime Narioka
    2002 Volume 89 Pages 15-24
    Published: 2002
    Released: October 20, 2021
    JOURNAL FREE ACCESS
    Since macropores significantly influence the movement of water and air in the soil, it seems that the structure of macropores should determine the processes of drainage. A study was conducted to investigate the structure of macropores and the associated drainage process. The drainage characteristics of volcanic ash and paddy field soils were investigated, and the following results were obtained. (i) The structure of entry pores depended on the direction of sampling. We constructed a model of entry pore structure, and found that this phenomenon is thought to reflect the shape of drainage macropores, especially the joints of tubular pores that have different diameters. (ii) The results of drainage experiments using a 100 cm3 cylindrical sampler were thought to have been greatly affected by the inner wall of the sampler. Nevertheless, it could be said that wall-affected results show soil drainage characteristics better than non-wall-affected results. We constructed a model of drainable macropores structure to explain this phenomenon. The shapes of pF-distribution curves were different depending on the direction of sampling when soil was sampled using a 100 cm3 cylindrical sampler. This could be explained by assuming that large tubular pores in the network of macropores were in a vertical direction and smaller tubular pores were in a horizontal direction.
    Download PDF (3386K)
  • Kouji Kameyama, [in Japanese], Tomoyasu Ishida, Hidemasa Kato
    2002 Volume 89 Pages 25-33
    Published: 2002
    Released: October 20, 2021
    JOURNAL FREE ACCESS
    The prediction method of ion concentration in the effluent during pH 3 sulfuric acid solution permeation into the air-dried volcanic ash soil column was examined in this study. The method for prediction was composed of chemical reactions between acid solution and soil, and mixing cell model. The chemical reactions were composed of aluminum dissolution, cation exchange between dissolved aluminum and basic cations, bicarbonate formation, sulfate ion adsorption, charge valance and mass balance of sulfate ion and basic cations. Cation exchange between dissolved aluminum ion and soil bases were lumped together with the mineral weathering as acid buffering effect. Mixing cell size depends on dispersivity and that value was determined by the breakthrough curve during KC1 and pH 3 sulfuric acid solution permeation. Characteristics of the variable charge on volcanic ash soil were considered in the simulation model by applying the anion adsorption equation (Wada,1981)in which adsorbed amount of sulfate ion depends on pH and sulfate ion concentration. The simulation results agreed well with the measured values of pH, aluminum ion concentration and cumulative release of basic cations in the effluent. These represent the most serious effects of the acid deposition on the soil. Therefore, parameters used in this simulation model are useful for predicting the main effect of the acid deposition on the Kanto loam subsoil. However, it could not estimate basic cations concentration of the effluent with good accuracy. This discrepancy may reflect the assumptions that cation exchange treated as aluminum-divalent basic cation exchange, the equilibrium constant was assumed and exchange between hydrogen ion and cation was not included. Therefore, it is necessary to describe the cation exchange in more detail.
    Download PDF (1179K)
  • Chaiyanam Dissataporn, Kane Yacouba, Machito Mihara, Rokuro Yasutomi
    2002 Volume 89 Pages 35-42
    Published: 2002
    Released: October 20, 2021
    JOURNAL FREE ACCESS
    Saline affected soil is in the northeast of Thailand, especially in the Khon Kaen Province. The relation between the salinity accumulation in brackish groundwater and the groundwater level from ground surface represents the progress state of soil salinization. The practice for suitable land use against the salinization can be established when the main conditions of salinization hazards are known. Based on this concept, the electric conductivity (EC) of groundwater and its level were measured with piezometers for three years in an experimental field at Khon Kaen Province. The field data showed that the groundwater level much affected by salinity was less than one and half meters from ground surface in the investigated area, and it was confirmed that the saline soil was mainly caused by the capillary rise of brackish water and by the accumulation of salt occurred at the soil surface. Salt accumulation process was investigated by the change in groundwater level. The reducing effect of salinization caused by capillary water rise became remarkable when the groundwater level was lowered until ground surface soil was out of the dominant capillary water zone. This indicates the reduction of groundwater level was very effective in reducing salinization. Allowing for field experimental results, a classification map for environmental land use in saline affected area was proposed.
    Download PDF (923K)
  • Chaiyanam Dissataporn, Hajime Narioka, Pramot Yamclee, Somsri Arunin
    2002 Volume 89 Pages 43-53
    Published: 2002
    Released: October 20, 2021
    JOURNAL FREE ACCESS
    The electromagnetic induction terrain conductivity meter, “EITCM”,has been used for the salinity assessment in salt-affected soils in northeastern Thailand. This paper briefly discusses the applicability of the electromagnetic method for delineating the salt distribution within the landscape and determining the salt content in soil at the depth up to 30 m. This information together with hydrological data and present landuse is useful for the base of the salinity management in northeastern Thailand. A case study presented the results of the use of the electromagnetic terrain conductivity meter in some major salt-affected soils of Nakhonratchasima province. The results of the investigation revealed that the source of salt in the process of soil salinization underlies the salt-affected soils. High-elevated areas play an important role for the water supply in the process of soil salinization. Variations of the reading might be due to the salt content, moisture content and soil type. Accuracy of the reading must be carefully considered when the survey for soil profiles is carried out in the areas where high clay content and low moisture content.
    Download PDF (3831K)
  • [in Japanese]
    2002 Volume 89 Pages 61
    Published: 2002
    Released: October 20, 2021
    JOURNAL FREE ACCESS
    Download PDF (352K)
feedback
Top