This study was conducted on a Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric haplocalcids) with approximately 1% slope.  Inflow water rates were set at 28 Lpm in each furrow in September 1998 and April 1999.  The water source was from the Snake River with pH=8.2, EC=0.5 dS/m, and SAR=0.7.  Small trapezoidal, long-throated flumes were installed 18.3-m down-slope to measure runoff and to faciliate sampling to estimate sediment and P losses at 5, 15, 45, 75, 135 and 255 min after runoff began.  Sediment load was estimated by the 1-L Imhoff cone technique.  Ortho-P was determined on a filtered (0.45 um) sample, while Fe-O (iron oxide strip) and total-P (persulfate digestion) were determined on an unfiltered sample.  Soil samples (0-3 cm) were taken from the furrow bottom immediately before each irrigation for Olsen-P, FeO-P and water soluble-P determination. Olsen-P was also determined on a 0-30 cm spring soil sample from each plot. Runoff data were integrated over time to calculate cumulative and average effect for a furrow during an irrigation and subjected to statistical regression analysis.