A Consideration on Effect of Sample Area on Measured Statistical Distributions of Soil Physical Properties in Plow-sole of a Paddy Field from a Viewpoint of Soil Pore Structure

Abstract

The effect of the sample area on the statistical distributions of soil physical properties obtained from the plow-sole in a paddy field was examined from a viewpoint of the soil pore structure. Soil samoles were collected with three samplers of different area (6.9, 19.6, 41.2cm²) from the plow-sole in a paddy field and five physical properties such as bulk density were measured in the laboratory experiments. The effect of the sample area on the distribution sof volumetric water content, bulk density, gravimetric water content and volume percenrage of water drained from saturation to the suction greater than 4.9kpa was relatively small and it was statistically equivalent to the fact that the effect of the sample area on the distributions of specific water capacity in suctions greater than 4.9kpa was relatively small. Therefore the area of about 7cm² was sufficient to estimate the distributions of these properties. In addition, the effect of the sample area on the distributions of saturated hydraulic conductivity and volume percentage of water drained from saturation to the suction less than 4.9kpa was relatively large and it was closely related to the fact that the effect of the sample area on the distributions of specific water capacity in suctions less than 4.9kpa was relatively large. Hence, at least the area of 41.2cm² wasneeded to estimate the distributions of these properties.