Garden with Insight v1.0 Help: Phosphorus - Mineralization

The P mineralization model developed by Jones et al. (1984) is similar in structure to the N mineralization model. Mineralization from the fresh organic P pool is estimated for each soil layer with the equation [Equation 206] where RMP is the mineralization rate of fresh organic P in layer l in kg/ha and FOP is the fresh organic P in crop residue in kg/ha.

Equation 206

RMP = DCR * FOP
Code:
same
Variables:
RMP = FreshPMineralizationForLayer_kgPha
DCR = decayRateConst
FOP = organicPFresh_kgPha

Mineralization of organic P associated with humus is estimated for each soil layer by using the equation [Equation 207] where HMP is the humus P mineralization rate in kg/ha and OP is the organic P content of soil layer l in kg/ha. The ratio of ON(a) to ON is used to in equation 207 to calculate the active portion of the OP pool. (It is the same proportion as in the N pool, I guess.) This eliminates the need for maintaining two OP pools corresponding to the ON(a) and ON(s) pools.

Equation 207

HMP = (CMN * ON(a) * OP * sqrt(SWF * TF(n)) * sqr(BD)) / (ON * sqr(BDP))
Code:
same except for multiplier of 1.4
HMP = 1.4 * HMN * OP / ON
HMN = CMN * ON(a) * sqrt(SWF * TF(n)) * sqr(BD) / sqr(BDP)
so HMP = 1.4 * (CMN * ON(a) * OP * sqrt(SWF * TF(n)) * sqr(BD)) / (ON * sqr(BDP))
note that this must be done after n mineralization
Variables:
HMP = HumusPMineralizationForLayer_kgPha
HMN = activeHumusNMineralization_kgPha
ON = organicNTotalHumus_kgPha
OP = organicPHumus_kgPha

To maintain the P balance at the end of a day, humus mineralization is subtracted from the organic P pool, residue mineralization is subtracted from the FOP pool, 20% of RMP is added to the OP pool, and 80% of RMP is added to the labile (fresh) P pool.