Logistic growth approach

In this approach the growth is proportional to the potential uptake of nitrogen. The uptake of carbon in annual plants starts and ends at day numbers specified by the parameters Up Start and Up End. Note that if the growth starts late one year, for example if an autumn crop is simulated or if the crop is grown on the southern hemisphere, the Up Start and Up End values should still be given as the calendar day when the growth starts and ends respectively. Perennial plant growth is simulated the whole year. (It can be useful to compare the Up Start and Up End values with the fixed emergence day number and harvest day number).

The growth, C_Atm→a (i.e. photosynthesis), is calculated as:

                                    (5.6)

where cn_p is a parameter, E_ta is the actual transpiration and E_tp is the potential transpiration. The response function for water f(E_ta/E_tp) is simply the ratio itself.

The potential uptake of nitrogen N_s→pl,p is given as:

                                             (5.7)

where p_ua, p_ub and p_uc are parameters and ∆t is the time since the start of growth. See viewing function Potential uptake of nitrogen – logistic growth.