INFLOW RATES AND INTERRUPTED FLOW EFFECTS ON CONCENTRATED FLOW EROSION AND INTAKE RATE IN TWO SOILS

Abstract

Surface irrigation is the most widely used irrigation practice worldwide, but its water use efficiency is low. Interrupted supply of water to furrows may reduce intake rate (IR) upstream and improve irrigation efficiency in many soils, but has an insignificant effect in others. Similarly, intermittent supply of water in furrow irrigation reduces furrow erosion in many soils but not in others. It is hypothesized that the response of soils to interrupted flow is affected by soil texture and structural stability combined with the rate of furrow wetting as determined by inflow rates. The objective of this study was to investigate the effects of inflow rate at the wetting stage of the soils and type of flow (continuous and interrupted flow) on IR and soil loss in concentrated flow. Two soils (a silt loam, Calcic Haploxeralf, and clay, Typic Haploxerert) were packed in miniflumes and were exposed to three inflow rates of concentrated (rill) flow. Cumulative intake in the clay was higher than that in the silt loam because of more stable aggregates in the clay. Increase in inflow rates had no effect on cumulative intake in both soils exposed to continuous flow because even the low inflow rate was high enough to cause aggregate disintegration similar to that in the high inflow rates. Interrupted flow reduced IR in the clay and had a small effect in the silt loam because of more soil surface compaction in the clay during the flow interruption. Soil erosion in continuous flow increased by 320% with the increase in inflow rates (and flow shear force) in the clay and only by 30% in the silt loam. Interrupted flow reduced erosion in both soils with the effect being more pronounced in the clay. Flow interruption reduced soil loss because it increased the cohesion forces between surface soil particles and the bulk soil underneath. These results suggested that flow interruption in furrow irrigation could be considered as an effective management tool for the control of water intake and erosion in furrow irrigation.