Modelling water pollution by leached soluble phosphorus, part 1: Calibration of the ANIMO model

The ANIMO model, linked to a multi-layer hydrological model, has been used for simulating soluble phosphorus (P) leaching, from fields with tile drainage, with an emphasis on leaching following spreading of organic manures. The model has been calibrated using data for oxalate extraction of P, iron and aluminium for soils at test sites, and validated using measured time-series data for leached P in outflows from tile drains on a dairy farm. The model has been shown to give good representation of soluble organic P leaching, which is at a high level for an extended period following manure spreading. However, although it simulates soluble inorganic P leaching, it is unable to represent colloidal inorganic P losses which are also at high levels (but particularly during the first few days) following spreading of organic manures. Hence soluble inorganic P losses simulated are much lower than measured inorganic P loss. Representation of inorganic P losses using ANIMO is less satisfactory than using another model which does include representation of colloidal P losses, as described in a previous study using the same time-series dataset for leached P.