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# Field Capacity

Unlike natural soil conditions, the field capacity of a biozone dynamically changes with time due to the development of filamentous material of live bacterial biomass allowing the biozone layer to retain additional water. Therefore, temporal change in the biozone field capacity is related to the amount of biomass in the layer. This is shown by the equation:

              $$\theta\_f^t=\theta\_f^{t-1}+\Phi\*(\theta\_s^{t-1}-\theta\_f^{t-1})^{\xi}\frac{\[\frac{d(Bio)}{dt}]}{10\*\rho\_{bm}}$$                                                                 (6)

where $$\theta\_f^t$$ is field capacity at the end of the day (mm), $$\theta\_f^{t-1}$$ is field capacity at the beginning of the day (mm), $$\theta\_s^{t-1}$$ is saturated moisture content at the beginning of the day (mm), $$\rho\_{bm}$$ is the density of live bacterial biomass (\~1000 kg/m3$$\Box \Box \Box$$), Φ is field capacity coefficient 1 (unitless), and $$\xi$$  is field capacity coefficient 2 (unitless).


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