Garden with Insight v1.0 Help: Soil patch next day functions: for the top soil layer, calculate nitrate lost in runoff, lateral flow, and percolation

Calculations of nitrate lost in water flow are different for the top soil layer than for the other soil layers. First, water running off the surface of the soil takes some nitrate with it. Note that nitrate in rainfall and snowmelt was already added to the soil without considering runoff, so we must adjust that here. For the top soil layer, which is always 10 mm deep, nitrate lost in lateral flow and runoff can be lumped together because the two water flows are virtually indistinguishable at the soil surface.

All of the nitrate losses here use a common equation, which depends on the amount of nitrate in the layer, the volume of water flowing through the layer, and the porosity of the layer (higher porosity = more ease of flow). For nitrate lost in runoff and lateral flow from the surface layer, the water volume is runoff plus lateral flow from the top layer. For nitrate lost in percolation rom the top soil layer, percolated water is the important water volume.

calculation of nitrate lost from lower soil layers, rainfall, snowmelt, runoff, lateral flow and percolation
EPIC Nitrogen Loss Through Leaching, Surface Runoff, and Lateral Subsurface Flow
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