Relation of some Soil Water-transmission Characteristics to some Soil Physical Properties in a Tropical Alfisol

Abstract

A study was conducted to determine soil physical properties of an Alfisol constituting the soil of a proposed tillage and irrigation water management field laboratory and to relate the physical properties to the water transmission characteristics. The soil was found to be mainly sandy loam on the surface with high infiltration rate and dense concretionary sub-surface layers with low hydraulic conductivity which restricted water movement of water down the profile and facilitated sub-surface lateral movement of water down the slope. Saturated hydraulic conductivity correlated negatively with bulk density (r = -0.239**), clay content (r = -0.290**), gravel content (r = -0.131*); but positively correlated with porosity (r= 0.235**) and sand content (r=0.256**) (r=correlation coefficient;**=significant at ≤ 5% level; * = significant at10% level). The available water content estimated as the water content between the 100cm and15000cm matric tensions was well predicted with a linear multiple regression equation from the bulk density and gravel, sand, silt, clay and organic carbon contents with a co-efficient of determination (R2) of 59.5%. The average 48-hour post infiltration water content in the top 30cm depth was lower than the estimate of water content at field capacity from laboratory-determined water retention at 100cm matric tension. This suggests that irrigation scheduling in the soil based on the laboratory estimate of available water content may overestimate the intervals between irrigation water applications. JARD Vol. 1 2001: pp. 9-22