Sediment and Phosphorus Transport in Irrigation Furrows

Abstract

Sediment and phosphorus (P) in agricultural runoff can impair water quality in streams, lakes, and rivers. We studied the factors affecting P transfer and transport in irrigated furrows in six freshly tilled fallow fields, 110 to 180 m long with 0.007 to 0.012 m m ' slopes without the interference of raindrops or sheet flow that occur during natural or simulated rain. The soil on all fields was Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids). Flow rate, sediment concentration, and P concentrations were moni-tored at four, equally spaced locations in each furrow. Flow rate de-creased with distance down the furrow as water infiltrated. Sediment concentration varied with distance and time with no set pattern. Total P concentrations related directly to sediment concentrations (r2 = 0.75) because typically>90 % of the transported P was particulate P, emphasizing the need to control erosion to reduce P loss. Dissolve