Garden with Insight v1.0 Help: Plant next day functions: calculate aeration growth constraint

Having an aeration growth constraint on general growth is a little strange, because you would think that aeration stress (i.e., no air in the soil because it is full of water) would affect root growth more. Too little air in the soil affects the plant primarily by the fact that root respiration is hampered because the roots need oxygen to respire. Actually poor root respiration reduces the uptake of water and nutrients, and chemical changes in the soil can produce toxins that limit overall plant growth. So poor soil aeration has a wider effect on plant growth in general than just on root growth.

The aeration growth constraint depends on the soil water content in relation to the soil porosity in the top meter of soil, a critical aeration factor for the plant, and an S curve describing the effect of poor aeration on general plant growth. The amount of soil water in the top meter of soil is divided by the porosity in the top meter of soil to get an index of waterlogging. The critical aeration factor is the fraction of that waterlogging index at which the plant starts to experience reduced growth. Most plants have a critical aeration factor of about 0.85. Rice has a great tolerance for waterlogging and will tolerate a waterlogging index of 1.0 without ill effect.

calculation of general growth constraint
EPIC Constraints
Model contents