# Humus Mineralization

Phosphorus in the humus fraction is partitioned between the active and stable organic pools using the ratio of humus active organic N to stable organic N. The amount of phosphorus in the active and stable organic pools is calculated:

     $$orgP\_{act,ly}=orgP\_{hum,ly}\*\frac{orgN\_{act,ly}}{orgN\_{act,ly}+orgN\_{sta,ly}}$$                  3:2.2.3

     $$orgP\_{sta,ly}=orgP\_{hum,ly}\*\frac{orgN\_{sta,ly}}{orgN\_{act,ly}+orgN\_{sta,ly}}$$                  3:2.2.4

where $$orgP\_{act,ly}$$ is the amount of phosphorus in the active organic pool (kg P/ha), $$orgP\_{sta,ly}$$ is the amount of phosphorus in the stable organic pool (kg P/ha), $$orgP\_{hum,ly}$$ is the concentration of humic organic phosphorus in the layer (kg P/ha), $$orgN\_{act,ly}$$ is the amount of nitrogen in the active organic pool (kg N/ha), and $$orgN\_{sta,ly}$$ is the amount of nitrogen in the stable organic pool (kg N/ha).

Mineralization from the humus active organic P pool is calculated:

$$P\_{mina,ly}=1.4\*\beta\_{min}*(\gamma\_{tmp,ly}*\gamma\_{sw,ly})^{1/2}\*orgP\_{act,ly}$$         3:2.2.5

where $$P\_{mina,ly}$$ is the phosphorus mineralized from the humus active organic $$P$$ pool (kg P/ha), $$\beta\_{min}$$ is the rate coefficient for mineralization of the humus active organic nutrients, $$\gamma\_{tmp,ly}$$ is the nutrient cycling temperature factor for layer $$ly$$, $$\gamma\_{sw,ly}$$ is the nutrient cycling water factor for layer $$ly$$, and $$orgP\_{act,ly}$$ is the amount of phosphorus in the active organic pool (kg P/ha).

Phosphorus mineralized from the humus active organic pool is added to the solution P pool in the layer.