Simulation of growth, development and yield of canola (Brassica napus) in APSIM

The canola (Brassica napus L.) module in the Agricultural Production Systems Simulator (APSIM) was developed in the late 1990s. There has been no peer-reviewed account of the scientific underpinnings of the module, despite considerable testing across a wide range of environments in the Australian grains industry and numerous applications of the model to address agronomic and crop adaptation issues. This paper presents a summary of the parameters in the module and reviews the physiological evidence justifying their values and module performance, and reflects on areas of module improvement and application. APSIM-Canola simulates crop development, growth, yield and nitrogen (N) accumulation in response to temperature, photoperiod, radiation, soil water and N supply, with a daily time-step, using well-accepted approaches. The module has been validated on more than 250 data points across Australia, China, and Germany and typical root mean squared deviations for days to flowering are similar to 5 days and for grain yield are similar to 0.4tha(-1). Testing on vernalisation-responsive winter types and in high yielding situations has indicated that more research is required to define phenology parameters and yield forming processes in high yielding environments. There is a need to develop better predictive routines for grain oil content that take account of the dynamics of grain filling and interactions with environmental conditions, and improve upon current regression-type approaches. Further testing of N responses is required. Physiological characterisation of new cultivar types, such as hybrids, Indian mustard (Brassica juncea), and new herbicide tolerance types is required to make the module more applicable to contemporary canola production systems. A lack of understanding of the effects of high and low temperature extremes on reproductive processes is currently limiting the use of the module outside conventional sowing dates and agro-climatic zones.