Dripper discharge rates and the hydraulic properties of the soil

The hydraulic properties of soils are needed in predicting runoff and erosion, irrigation design and general transport phenomena in the soil. Theoretical tools have been developed to estimate them from measurements of water distribution near a point source assuming stable homogeneous and isotropic soils. Soil wetting rate and its interaction with soil texture was not considered in these analyses even though reports indicated that a high wetting rate disintegrates soil's aggregates and is associated with deterioration of soil structure and reduction of the hydraulic conductivity (HC) and infiltration rates (IR) especially in clay soils. Objectives were to: (i) show how IR of a soil, wetted from a point source, are affected by the discharge rate of the dripper. (ii) identify the mechanisms responsible for this reduction and (iii) investigate the effect of emitter's discharge on the resultant HC of sand,loam and clay. We related the reduction of IR under high emitter discharge to the breakdown of soil aggregates by fast wetting and deterioration of the hydraulic properties of soils, (the pedological mechanism,). Results show that relative to the ideal stable soil the steady IR decreased with an increase in the discharge rate of the dripper. The resultant saturated HC (K₅) was, erroneously, negative for clay and loamy soils but not for sand. When determining hydraulic properties of soils with a point source, low discharges should produce better results especially in soils with medium to high clay content.