Simulating the role of rooting traits in crop-weed competition

Tailoring root systems to particular cropping systems is of interest in Australia's challenging cropping soils. The capacity to better match root systems to the environment in which they grow offers the potential to improve crop productivity. In this study, the ROOTMAP model of crop root growth was used to screen combinations of rooting traits and cropping environments, to identify rooting characteristics important for crop productivity. This study focussed on grain crops growing as perfect weed-free monocultures or in competition with weeds. A sensitivity analysis approach was used to investigate 30 parameters that describe root architecture, the cropping environment and agronomic management. Parameters were ranked in order of importance for water, nitrogen and phosphorus uptake. Parameters controlling the efficient distribution of roots through soil (geotropism index, deflection index, branch angle), and physiological parameters determining the rate of phosphate influx into roots (P uptake kinetics), ranked highest for weed-free crops. In contrast, the most important parameters for plants in competition with weeds were those controlling the intensity of soil foraging (plant density and branch spacing) and rate of root system establishment (relative root growth rate), highlighting the importance of quickly and effectively occupying the soil volume during establishment if a crop is to out-compete weeds. This separation of characteristics into those of greatest benefit to weed-free crops or in crop-weed competition, suggests that there is the potential for tailoring root characteristics to specific conditions. (C) 2007 Elsevier B.V. All rights reserved.