RIMPhil: a bioeconomic model for integrated weed management of annual barnyardgrass (Echinochloa crus-galli) in Philippine rice farming systems

This paper describes a complex, dynamic simulation model that has been developed for the analysis of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice farming systems in the Philippines. Users of the model may simulate any feasible combination of 49 weed treatments options across wet and dry cropping seasons over 5, 10, 15, and 20 year periods, subject to a predetermined sequence of planting methods. The main outputs of the model include weed seed and plant densities and seasonal and annualised profit over the simulated planning horizon. Model output emphasises the substantial economic benefits associated with effective long-term weed management strategies. In addition, the most-profitable weed densities are found to be much lower than those usually recommended to producers, indicating the importance of considering economic factors in the formulation of management recommendations. Results broadly indicate that a mixture of chemical and non-chemical treatments provides good weed control in rice crops, and maximises long-term profit for systems where the main weed is annual barnyardgrass. However, the performance of this strategy is influenced by crop establishment method and weed density level. These indicative results emphasise the value of the model for guiding the efficient control of annual barnyardgrass in rice crops in the Philippines.