A Simple Functional-Structural Plant Model for Sugarcane.

Sugarcane crop is the main source of sugar and the second largest source of biofuel in the world. In contrast to other crops all aerial parts are harvested and processed increasing the importance of its structures composition (sugars and fiber). Moreover, different row spacings have been adopted on sugarcane fields to decrease damage to plants and soil structure from harvest equipment though potentially can affect the tillering process and productivity due to increased shading. Functional-structural plant (FSP) models are capable to simulate plant growth under competition for light at organ level and have been used to assess and optimize crop arrangements and intercropping for other cultures. The aim of this paper was to develop and test a simple FSP model to simulate sugarcane growth and development, notably the tillering process and sucrose build-up. The FSP model was developed by integrating the main crop components from organ level (phytomer) based on a relative source-sink approach and a robust light model embedded into a three-dimensional modelling platform (GroIMP). The effect of soil water content on plant extension was added with a soil-plant-atmosphere with a tipping bucket water balance routine implemented in the model. A sugarcane field experiment dataset, with a standard row spacing (1.40 m), was used for parameters deriving and model evaluating and testing. The FSP model was able to simulate sugarcane above dry biomass (r²=0.87, d=0.91), stalk dry mass (r²=0.87, d=0.84), sucrose content (r²=0.57, d=0.49) and tillering (r²=0.87, d=0.95) satisfactorily. Further model testing against experimental data may be done to better assess the model applicability for different spacing rows arrangements.