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.