2012 ©
             Publication
Journal Publication
Research Title Spatial variability of Electrical Conductivity of salt-affected soils in Northeast Thailand 
Date of Distribution 12 June 2014 
Conference
     Title of the Conference The 20th World Congress of Soil Science 
     Organiser Korean Society of Soil Science and Fertilizer, Rural Development Administration(RDA), International Union of Soil Sciences (IUSS) 
     Conference Place international convention center jeju  
     Province/State South Korea 
     Conference Date 8 June 2014 
     To 13 June 2014 
Proceeding Paper
     Volume
     Issue
     Page O57-5 
     Editors/edition/publisher  
     Abstract The problem of soil salinity represents a major challenge to agriculture and environment in Northeast Thailand. Careful assessment of the status and spatial variation of salt-affected soils is required to implement appropriate control measures and to secure sustainable land uses. Currently, mapping classes of these soils is based on the percentage of salt crusts formed on the soil surface. Scant information is available on the spatial correlation and, in turn, the spatial variability of the electrical conductivity (EC). The objective of this study was to describe the spatial variability of soil electrical conductivity of the saturation extract (ECe) in areas of different degrees (classes) of salt-affected soils using geostatistics which is an essential tool for this purpose. Attention was on areas of very severely salt-affected soils (class 1), severely salt-affected soils (class 2), and moderately salt-affected soils (class 3). For each class, two study sites were chosen, totally six sites were taken into consideration. Soil samples were collected according to the stratified systematic unaligned sampling method in the dry season of 2012. In each site, a representative area of 50x50 m2 was selected. This area was divided into 100 equivalent grids of 5x5 m2. Within each grid, one sample were randomly collected at 0-30 cm depth. Thus, a total of 600 soil samples (100 samples x 6 sites) were analyzed for the ECe. For the dataset obtained from each study site, geostatistics was applied to elucidate the spatial correlation of ECe. The semivariogram was created for this purpose. The Ordinary Least Square (OLS) method was applied to fit the semivariogram model. The best-fit model (i.e., spherical or exponential) was determined based on the coefficient of determination (R2). Corresponding parameters including nugget, range, and sill values obtained from this model were used to describe the spatial correlation. To generate the relevant spatial variability map, these three parameters were employed in the kriging interpolation. The results showed that the salinity levels as indicated by the ECe values were very strongly saline (ECe 56.70- 433 dS m-1), normal to very strongly saline (ECe 0.16- 49.00 dS m-1), and normal to slightly saline (ECe 0.11- 5.26 dS m-1) for areas of very severely salt-affected soils (class 1), severely salt-affected soils (class 2), and moderately salt-affected soils (class 3), respectively. For every study site, the semivariogram model fitted well with the semivariogram samples (R2 0.73-0.98). When using the semivariograms to describe the spatial correlation of the ECe, it was found that the variation was generally high. It varied between classes and within the same class. The range values were 190 and 8 m, 34 and 61, and 170 and 16 m. for both study sites of classes 1, 2, and 3, respectively. The shorter the range, the higher the variation. The nugget effect varied between study sites indicating the uncertainty of the occurrence of the spatial sources of variation. Based on the salinity maps generated using the kriging interpolation, the areas of class 1 were entirely very strongly saline soils (EC > 16 dS.m-1). For the areas of class 2, very high variation in salinity levels was found ranging from normal (EC < 2 dS.m-1) to very strongly saline soils. In the areas of class 3, the soils varied slightly from normal to very slightly saline (EC > 2-4 dS.m-1). The information on spatial variation of ECe is very important for soil management especially in the areas of class 2, because these areas includes a large variety of salinity levels, ranging from normal to very strongly saline. In areas of classes 1 and 3, this information is less important because in the class 1 areas the soils, even though highly varied, were entirely very strongly saline. No arable crops can be grown on these areas. On the other hand, in the areas of class 3, the soils were generally normal to very slightly saline. There is very slightly effect on crop growth especially in the growing (rainy) season.  
Author
537030026-1 Miss PORNTIP PHONTUSANG [Main Author]
Agriculture Doctoral Degree

Peer Review Status มีผู้ประเมินอิสระ 
Level of Conference นานาชาติ 
Type of Proceeding Abstract 
Type of Presentation Oral 
Part of thesis true 
Presentation awarding false 
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