Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 16, 2001
Publication Date: N/A
Interpretive Summary: Water runoff and soil erosion can take place from overhead sprinkler irrigation systems as well as from furrow irrigation practices. If phosphorus (P) in runoff water, or that carried with eroded soil, reaches lakes and streams it may cause lessening of dissolved oxygen in the waters, favoring algal and other plant growth over that of animal life. Phosphorus in runoff may be influenced by irrigation water quality and on whether the soil surface is wet or dry, loose or crusted. To evaluate water quality effects on P in runoff we used reverse osmosis water (similar to rain water) and a mix of reverse osmosis and well water (similar to river irrigation water) in a laboratory sprinkler study. We used a calcareous soil in our tests and to provide a wide range of P in the soil some of the soil had either been amended or not amended with manure and/or with cheese whey. We placed samples of each soil treatment in large steel boxes (4 x 5 feet) and irrigated three times on each sample. First irrigation was on a dry loose surface; second, on a wet surface; and third, on a dry crusted surface. Following each irrigation we determined runoff, sediment, and P in the runoff. We conclude that, on the calcareous soil we used, water with similar chemical constituents to that of the soil, and water that quickly dissolves chemical constituents found in calcareous soils, give equal results when studying P runoff relationships as pertaining to potential contamination of lakes and streams. In the same vein, soil surface conditions had little or no effect on amount of P in runoff from this calcareous soil. Rather, P coming off the soil depended on amount of soil eroded and amount of P in the parent soil.
Technical Abstract: Phosphorus (P) in runoff from overhead sprinkler irrigation systems as well as from furrow irrigation practices may enrich offsite water bodies & streams & may be influenced by irrigation water quality & soil surface conditions. Runoff, soil loss, & P in runoff using reverse osmosis (RO) water & a mix of RO & well water (RO/Tap) was studied in a laboratory sprinkler study to evaluate water source effects on P transport. A top- or subsoil Portneuf silt loam (Durinodic Xeric Haplocalcid), either amended or not amended with manure &/or with cheese whey, with Olsen-P from 20 to 141 mg/kg & lime from 108 to 243 g/kg were placed in 1.5 x 1.2 x 0.2 m deep containers with 2.4% slope & irrigated three times from 3-m height for 15 min, applying 20 mm water. First irrigation was on dry loose surface; second, on wet surface; & third, on dry crusted surface. We took surface soil samples prior to first irrigation for Olsen-P, water soluble P, & FeO-P analyses. Following each irrigation we determined runoff, sediment, dissolved reactive P (DRP) in filtered samples, & FeO-P & total-P in unfiltered samples. Soil surface conditions had no effect on P runoff relationships. Regression coefficients were generally greater for RO/Tap water, but type of water had no significant effect on relationship between DRP or FeO-P runoff & soil test P, except for DRP in RO runoff vs. water soluble soil P (r squared = 0.90). There was no correlation between total-P in RO runoff & soil P; for total-P in RO/Tap runoff versus soil test P, r squared was <0.50. Water source & soil surface conditions had minimal effect on P runoff from this calcareous soil. The best predictor of P in runoff depended on combination of soil P fraction & P fraction in runoff.