Potential Biomass Production

Crop biomass growth is represented in terms of biomass accumulation (including above-ground biomass and, possibly, below-ground storage organ biomass such as root and tuber), which occurs during active growth until maturity (see Crop development). Crop biomass production is dependent on: intercepted radiation (radiation-dependent), transpiration (water-dependent), and nitrogen uptake (nitrogen-dependent). Each of these factors is capable of limiting growth.

During each simulation day, the potential biomass production for the day (BP d, kg m -2 d -1 ) is taken as the minimum of transpiration-dependent (BT d, kg m -2 d -1 ; Tanner and Sinclair, 1983) and radiation-dependent biomass production (BIPAR d, kg m -2 d -1 ; Monteith, 1977):

where VPD (kPa) is the daytime mean atmospheric vapour pressure deficit, IPARd (MJ m -2 d -1 ) is the daily amount of intercepted photosynthetically active radiation, T ' P d (kg m -2 d-1) is the daily potential transpiration, KBT (kPa) is the crop biomass-transpiration coefficient, e (kg MJ -1 ) is the radiation-use efficiency, f(T) is a temperature-adjustment factor - in the range from 0 (full stress) to 1 (no stress) - equal to:

T mean (°C) is the mean daily air temperature, computed as:

T b (°C) and T opt (°C) are base and optimum air temperatures for growth.

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