Physical properties of the main soil series of northeast Thailand
1996
Vidhaya Trelo-ges (Khon Kaen Univ., Khon Kaen (Thailand). Faculty of Agriculture. Dept. of Soil Science)
Most important soil series in the Northeast are Korat and Roi-et soil series which cover 20 and 17 percent of the whole area, respectively. The study was done to a depth of 100 cm of soil. Soil texture were analyzed by sediment analysis for fine particles and sieve analysis for coarse particles. After analysis, the textural name given to Korat soil is sandy loam and Roi-et soil is loam. The soil water characteristic curves were determined by the hanging column method for the samples with soils of high water content, and by the pressure plate method for those soils with low water content. From the curves, the water content at field capacity of Korat soil was about 0.12, for Roi-et soil the value was 0.18 at the soil surface and about 0.30 at deeper than 75 cm. The water content at permanent wilting point of Korat soil was 0.05 and of Roi-et soil was 0.06 at the soil surface and 0.16 at a depth of greater than 75 cm. Bulk density values, measured from soil cores of 100 cubic m, were about 1.47 and 1.55 g/cubic m for Korat and Roi-et series, respectively. Porosity values, measured by using cored samples of 100 cubic m which were weighed at saturation and weighed again after oven drying, were 0.25 for Korat soil and 0.36 for Roi-et soil. The Falling head method was used to obtain the values of hydraulic conductivity of both soils. The average K-value for Korat soil was 103 cm/day but for Roi-et soil the values varied from 29 cm/day at soil surface to 0.9 cm/day at a depth lower than 75 cm. By using the double ring method, the constant infiltration rate of Korat and Roi-et soils were 78 and 6 mm/hr, respectively. The hydraulic conductivity and infiltration rate values of Roi-et soil were much lower than those of Korat soil. This means that water loss by percolation is greater in Korat soil than Roi-et soil.
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