Furrow Irrigation Water‐Quality Effects on Soil Loss and Infiltration

Abstract

Irrigation-induced erosion is a serious problem in the western USA where irrigation water quality can vary seasonally and geographically. We hypothesized that source-water electrical conductivity (EC) and sodium adsorption ratio (SAR = Na/[(Ca + Mg)/2]° 5, where concentrations are in millimoles of charge per liter) affect infiltration and sediment losses from irrigated furrows, and warrant specific consideration in irrigation-induced erosion models. On a fallow Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid), tail-water sediment loss was measured from trafficked and nontrafficked furrows irrigated with waters of differing quality. Treatments were the four combinations of low or high EC (0.6 and 2 dS m ') and low or high SAR (0.7 and 12 [mmol, L l]"). Slope is 1%. Twelve irrigations were monitored. Each furrow received two irrigations. Main effects for water quality, traffic, and first vs. second irrigations were significant for total soil loss, mean sediment concentration, total outflow, net infiltration, and advance time. Average tail-water soil losses were 2.5 Mg ha -' from low EC/low SAR furrows, 4.5 Mg ha-' from low EC/ high SAR furrows, 3.0 Mg ha' from high EC/high SAR furrows; and 1.8 Mg ha-' from high EC/low SAR furrows. Elevating water EC decreased sediment concentration from 6.2 to 4.6 g L -', but increasing SAR increased sediment concentration from 6.2 to 8.7 g L-'. Net infiltration decreased 14% in high SAR compared with low SAR treatments. Soil loss increased 68% for second irrigations, and net infiltration fell 23% in trafficked furrows, but water-quality effects were the same. Water quality significantly influenced infiltration and erosion processes in irrigated furrows on Portneuf soils. O F THE ESTIMATED 250 MILLION HA irrigated worldwide, at least 60% is surface irrigated. Soil erosion from irrigation, especially furrow irrigation, contributes to nonpoint-source pollution (Hajek et al., 1990) and is a serious threat to crop productivity in many regions (Carter, 1993).Agricultural research has focused primarily on rainfallinduced soil erosion, with comparatively little attention to furrow-irrigation-induced erosion. A common assumption has been that erosion in rills is mechanistically equivalent to that in irrigated furrows. While shear produced by concentrated flow causes soil detachment and entrainment in both, there are several important differences: (i) rill phenomenon often includes an additional force, raindrop impact, which detaches and transports adjacent soil particles to the rill stream; (ii) a furrow stream initially advances over dry soil, resulting in rapid wetting and destabilization of dry, low-cohesion soil aggregates and increased furrow erosion losses (Kemper et al., 1985), whereas rill soils are prewetted by precipitation; (iii) downstream flow rates decrease in furrows as water infiltrates, but increase in rain-fed rills owing mainly to tributary inflow, hence, furrow flow rates and potential erosion losses are greater in the upper reaches of a...

Phosphorus Runoff from Two Water Sources on a Calcareous Soil

“…2 dS m -1 ) and low SAR are preferable in irrigation water to prevent soil dispersion, reduce soil erosion, and increase infiltration because of strengthened soil bonds and heightened retention of soil aggregates (Lentz et al, 1996). There was a trace of Na + (0.6 mg L-1 ) in the RO water and no evidence of Ca" and Mg ++ , and therefore a low EC (0.02 dS m-1 ) and an undefined SAR.…”

“…Water quality available for runoff studies varies depending on source and may differ from rain water quality (Lentz et al, 1996). Therefore, a postulate is that water from various sources may influence runoff and P losses.…”

Wastewater and Magnetized Wastewater Effects on Soil Erosion in Furrow Irrigation

“…LENTZ et al (1996) determined that main effects for water quality, traffic, and first vs. second irrigations were significant for total soil loss, mean sediment concentration, total outflow, net infiltration and advance time. Average tail-water soil losses was also most for low EC/high SAR of water treatments and net infiltration decreased 14% in high SAR compared with low SAR treatments too.…”

Irrigation-Induced Erosion

“…Similarly, interactions of soil properties with water are largely limited to physical phenomena via slope, slope length, surface roughness, cover, etc. ; however, laboratory simulations and rain simulator studies (Levy et al, 1994;Shainberg et al, i 994;Kim and Miller, 1996;Flanagan et al, 1997aFlanagan et al, , 1997b as well as furrow irrigation studies (Lentz et al, , 1996 have demonstrated that EC and SAR significantly influence the erosive potential of a given shower or stream of water. Soil chemistry effects, to the extent that they exist in rainfed conditions, are indirectly integrated in rain-induced soil erosion models by affecting soil aggregation and dispersion on wetting.…”