Decision Support Systems: A Tool for Sustainable Weed Management

The use of simulation models as decision support systems can of fer an ideal means of achieving economical, environmentally safe and sustainable weed management. These systems can support weed management decisions for both soil applied and post-emergence weed control programs. Decision Support Systems based on weed economic threshold concepts have been developed in developed countries like United States and in some European countries in crops like soybean, com and wheat. The decision support systems that were developed in the initial days such as SOYHERB and CORNHERB are based only on herbicide efficacy and cost and did not include economic thresholds. More recent generation of weed management models such as WEEDSIM are based on weed economic threshold concepts and bioeconomic modelling, where weed seed bank and/or seedling population after emergence are also taken into account. Thus, the newest generation of weed management models evaluate the effect of a weed management program on crop yield in the current year and also in future years based on weed seed production. Applying herbicides only when economically justified of fers an opportunity to reduce chemical costs by eliminating unnecessary herbicide applications when weed pressure is low and also to reduce herbicide load in the environment. Most of the decision support systems on weed management are based on the weed density as the sole variable for estimating crop yield losses due to weeds. For reliable recommendations to be made, input requirements for the system should also include information on the relative time of emergence of crop and weed, crop density, environmental factors and fertiliser application in addition to weed density. A successful weed management decision support system should yield realistic weed monitoring procedures, and the long term bioeconomic implications of seed production by uncontrolled weeds.