Phosphorus (P) in runoff from furrow irrigated fields can impair water quality in streams, lakes
and rivers. We conducted a series of whole field studies to identify the factors affecting P transfer
and transport during furrow irrigation. Six irrigations were conducted on freshly tilled, fallow
fields that varied from 110 to 180-m long, with 0.007 to 0.012 m m-1 slopes. The soil on all fields
was Portneuf silt loam (coarse-silty, mixed superactive, mesic Durinodic Xeric Haplocalcids).
Flow rate, sediment concentration and phosphorus concentrations were monitored at four,
equally spaced locations in each furrow. Flow rate decreased with distance down the furrow as
water infiltrated. Sediment concentration varied with distance and time with no set pattern. Total
P concentrations were directly related to sediment concentrations (r2=0.75) because typically
>90% of the P was associated with particulates. Dissolved reactive P (DRP) concentrations
decreased with time at a specific furrow site but tended to increase with distance down the
furrow. DRP concentration correlated better with sediment concentration than extractable furrow
soil P concentration. However, DRP concentration was not appreciably affected by changes in
suspended sediment concentration later in the irrigation (>2 h). Combining sediment detachment-deposition with P desorption-sorption dynamics and sediment transport in the furrow will be
important to predict total P and DRP losses from tilled fields where erosion occurs.
See more of Phosphorus Chemistry in Soils: II. P Fluxes in Soil and Water Systems
See more of S11 Soils & Environmental Quality
See more of The ASA-CSSA-SSSA International Annual Meetings (November 6-10, 2005)