Garden with Insight v1.0 Help: Soil patch next day functions: in the first soil layer, calculate labile P loss in runoff and percolation

As with calculations for nitrate, calculations of labile mineral phosphorus lost in water flow are different for the top soil layer than for the other soil layers. Water running off the surface of the soil takes some labile P with it, and percolated water carries some labile P. Loss in lateral flow is not calculated for phosphorus, presumably because phosphorus is much less mobile than nitrate and tends to precipitate quickly out of solution.

Labile P losses in percolation and runoff are calculated together for the first soil layer. This equation is simpler than the water loss equations for nitrate. The concentration of labile P is calculated for water flowing through the soil using the amount of labile P in the layer and the weight of the soil layer. That concentration is simply multiplied by the amount of percolated water and by the amount of runoff water, and the resulting amounts of labile P are subtracted from the top soil layer.

calculation of nitrate loss in top soil layer, labile P loss in lower soil layers, runoff, percolation and lateral flow
EPIC Soluble P Loss in Surface Runoff (also includes percolation and lateral flow)
Model contents