SYSTEMS APPROACHES TO QUANTIFY CROP-WEED INTERACTIONS AND THEIR APPLICATION IN WEED MANAGEMENT

Studies to quantify crop-weed interactions have been conducted for decades, usually using empirical models that describe the relationship between weed density and yield loss. Quantitative insight into the behavior of the crop-weed system is needed to develop weed management systems. Recently, eco-physiological simulation models for crop-weed competition were introduced. These models simulate growth and production of species in mixtures, based on physiological processes in plants and their response to the environment. Such models help improve insight into the crop-weed system and can be used to develop simple predictive models for practical application. Several simple regression models for early prediction of yield loss by weeds have been developed. Recently, an approach has been developed in which the relative leaf cover of the weeds shortly after crop emergence is directly related to final yield loss. This approach has high potential as a predictive tool in weed control advisory systems. For strategic weed management activities, quantitative insight into the dynamics of weed populations is required However, many processes, such as seed bank dynamics, are not yet adequately understood to allow accurate prediction of future weed populations. The use of systems approaches to bridge the gap between weed science research and practical weed management is discussed.