Simulation of crop production in weed-infested fields for data-scarce regions

Weed infestation is a major yield-reducing factor that also decreases crop water productivity. Yet weeds are often neglected in crop productivity simulation studies, because existing empirical equations and mechanistic models are not widely applicable or have a high demand for input data and calibration. For that reason, AquaCrop, a widely applicable crop water productivity model, was expanded with a weed management module which requires only two easily obtainable input variables: (i) relative leaf cover of weeds, and (ii) weed-induced increase of total canopy cover. Using these inputs, AquaCrop directly simulates soil water content, crop canopy development and production as it is observed in weed-infested fields. Despite this simple approach, AquaCrop performed well to simulate soil water content in the root zone (relative root-mean-square error (RRMSE) of 5-13%), canopy cover (RRMSE of 15-22%), dry above-ground crop biomass during the season (RRMSE of 21-39%) and at maturity (RRMSE of 5-6%) and yield (RRMSE of 11-25%) of barley and wheat grown under different weed infestation levels and environments. The current study illustrates that the Aqua Crop model can be used to assess the effect of weed infestation on crop growth and production, using a simple approach that is applicable to diverse environmental and agronomic conditions, even in data-scarce regions.