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Phosphorus Runoff from Two Water Sources on a Calcareous Soil

Aase, J.K., Bjorneberg, D.L., Westermann, D.T.
Journal of environmental quality 2001 v.30 no.4 pp. 1315
water pollution, phosphorus, losses from soil, calcareous soils, silt loam soils, irrigated soils, sprinkler irrigation, soil analysis, runoff, Idaho
Phosphorus (P) in irrigation runoff may enrich offsite water bodies and streams and be influenced by irrigation water quality and antecedent soil surface conditions. Runoff, soil loss, and P fractions in runoff using reverse osmosis (RO) water or mixed RO and well water (RO/Tap) were studied in a laboratory sprinkler study to evaluate water source effects on P transport. A top- or subsoil Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid), either amended or not amended with manure and/or with cheese whey, with Olsen P from 20 to 141 mg kg and lime from 108 to 243 g kg, was placed in 1.5 × 1.2 × 0.2-m-deep containers with 2.4% slope and irrigated three times from a 3-m height for 15 min, applying 20 mm of water. The first irrigation was on a dry loose surface, the second on a wet surface, and the third on a dry crusted surface. Surface (ca. 2 cm) soil samples, prior to the first irrigation, were analyzed for Olsen P, water-soluble P (P), and iron-oxide impregnated paper–extractable P (FeO-P) analyses. Following each irrigation we determined runoff, sediment, dissolved reactive phosphorus (DRP) in a 0.45-μm filtered sample, and FeO-P and total P in unfiltered samples. Soil surface conditions had no effect on P runoff relationships. Water source had no significant effect on the relationship between DRP or FeO-P runoff and soil test P, except for DRP in RO runoff versus water-soluble soil P (= 0.90). Total P in RO runoff versus soil P were not related; but weakly correlated for RO/Tap (< 0.50). Water source and soil surface conditions had little or no effect on P runoff from this calcareous soil.