This lack of knowledge extends to crop models, which causes uncertainty when these are used for RS sensitive applications. In the Canesim model (Singels and Donaldson, 2000), canopy development (and interception of photosynthetically active radiation, PAR) is driven by thermal time. The RS effect is simulated by adjusting the thermal time requirement to reach 50% canopy by 125 8Cd (base of 10 8C) per metre change in RS. In the Canegro model (Inman-Bamber, 1991), a more complex approach is followed by simulating the development of individual leaves and tiller cohorts, both driven by thermal time. Leaf area index (LAI) is calculated by multiplying leaf area per tiller by tiller density. Fractional interception of PAR across cane rows (FIINTER) is then calculated according to Beer’s law. The RS effect is accounted for by simulating an increase in tiller appearance rate inversely proportional to RS. Tiller density is capped at 30 m2 . Simulated yield responses for the two models is then indirectly determined by the changed interception of radiation through its impacts on the rate of biomass accumulation and the rate of water consumption. The APSIM (Keating et al., 1999) and Qcane (Liu and Bull, 2001) sugarcane models do not account for differences in row spacing, as far as we could establish.