Parameterization of the MACRO model to represent leaching of colloidally attached inorganic phosphorus following slurry spreading

Abstract. The dual porosity soil water and contaminant transport model MACRO was tested for its suitability to represent water flows and leaching of phosphorus (P) through field drains following spreading of slurry. These flows are characterized by very high loadings of P, including a high proportion in colloidally attached form, for about one week following winter spreading of slurry, followed by quite a rapid decline to the low background level. Use was made of the option in MACRO for representing colloid facilitated contaminant transport. The model simulates transport through macropores and soil matrix pores (micropores) of contaminant carrying colloids, as well as trapping of colloids by straining and filtration using an adaptation of standard filtration equations. Calibration involved selecting soil hydraulic parameters, colloid filtration coefficients and P sorption characteristics for two soils from measured and literature values. Both P in solution and P attached to colloids were represented in simulated outputs. Reasonable agreement was found between simulated and measured water and leached P flows. Work with the model suggests that macropore flow through the soil to field drains of colloidally transported P is an important component of water pollution associated with slurry spreading

[1]  M. B. McGechan,et al.  SW—Soil and Water: A Review of Field Scale Phosphorus Dynamics Models , 2002 .

[2]  M. McGechan,et al.  SW—Soil and Water: Sorption of Phosphorus by Soil, Part 1: Principles, Equations and Models , 2002 .

[3]  M. McGechan.  Modelling Through Soil Losses of Phosphorus to Surface Waters , 2001 .

[4]  Ole H. Jacobsen,et al.  Field Investigations and Modeling of Particle‐Facilitated Pesticide Transport in Macroporous Soil , 2000 .

[5]  Paul J. A. Withers,et al.  Relating soil phosphorus indices to potential phosphorus release to water. , 2000 .

[6]  B. Ulén,et al.  Modelling particle mobilization and leaching in macroporous soil , 1999 .

[7]  P. Hooda,et al.  Phosphorus Loss in Drainflow from Intensively Managed Grassland Soils , 1999 .

[8]  N. J. Jarvis,et al.  Evaluation of a dual-porosity model to predict field-scale solute transport in a macroporous soil , 1999 .

[9]  P. Hooda,et al.  A comparative study of nitrate leaching from intensively managed monoculture grass and grass–clover pastures , 1998, The Journal of Agricultural Science.

[10]  A. Heathwaite,et al.  Transfer of colloidal forms of phosphorus in subsurface hydrological pathways , 1998 .

[11]  J. T. Douglas,et al.  Parameter selection and testing the soil water model SOIL , 1997 .

[12]  A. Vinten,et al.  A comparative study of nitrate leaching from soils of differing textures under similar climatic and cropping conditions , 1994 .

[13]  A. Vinten,et al.  Measurement of nitrate leaching losses from arable plots under different nitrogen input regimes , 1991 .

[14]  N. Barrow.  A mechanistic model for describing the sorption and desorption of phosphate by soil , 1983 .

[15]  A. Sharpley.  Prediction of Water-Extractable Phosphorus Content of Soil Following a Phosphorus Addition , 1982 .