Soil test phosphorus changes and phosphorus runoff losses in incubated soils treated with livestock manures and synthetic fertilizer

Abstract

Kumaragamage, D., Flaten, D., Akinremi, O. O., Sawka, C. and Zvomuya, F. 2011. Soil test phosphorus changes and phosphorus runoff losses in incubated soils treated with livestock manures and synthetic fertilizer. Can. J. Soil Sci. 91: 375–384. Source of phosphorus (P) and soil properties influence changes in soil test P (STP) concentrations and P runoff losses in manured and fertilized soils. We compared STP changes and P runoff losses in two soils, a clay loam and a sand, that were either unamended (control), or amended with liquid swine manure (LSM), solid cattle manure (SCM), or monoammonium phosphate (MAP) and incubated for 6 wk. Soil subsamples after incubation were analyzed for STP using Olsen (OP), Modified Kelowna (KP), Mehlich 3 (M3P) and water extraction (WEP) methods. We collected runoff from incubated soils for 60 min under a rainfall simulator, and analyzed for dissolved reactive P (DRP). Magnitude of STP increase in amended soils was greater in sand (19–48%) than in clay loam (7–37%). Increases in STP and DRP runoff concentrations in amended soils generally followed the order; MAP>LSM>SCM. Olsen P, KP and M3P were more accurate than WEP for predicting runoff DRP concentrations and loads, accounting for 43–49% of the variation in P concentrations for the first 30 min of runoff. Olsen P, the currently used STP method for environmental P regulation in Manitoba is sufficiently robust to predict runoff P losses from manure and fertilizer amended soils.