Predicting maize yield in a multiple species competition with Xanthium strumarium and Amaranthus retroflexus: Comparing of approaches to modeling herbicide performance

Abstract

A modeling approach based on weed relative leaf area (RLA) was used to describe the maize yield affected by weed competition and herbicide dose. The change of early RLA with herbicide dose was described using standard dose–response model. The dose response of individual weed species was included in a multivariate rectangular hyperbolic relationship between maize yield and weed relative leaf-area. Final model satisfactorily described the change of the weed relative leaf areas with herbicide dose in a multiple species competition with maize to reach a reasonable estimate of crop yield. Parameter estimates indicated that the maize yield could be about 11.23 t/ha in the absence of weeds. Applying herbicide at 0.29 rate of the recommended dose could decrease the Amaranthus retroflexus leaf area by 50%. For Xanthium strumarium, increasing the dose up to 0.58 rate of the recommended dose caused 50% reduction in early relative leaf area. The relative leaf area of the X. strumarium was 4.2-fold larger than that of the A. retroflexus at the time of herbicide application. Model validation indicated significantly better predictive ability of the leaf area model than that of the density model. Leaf area model permits to monitor the canopy (with considering the relative ground cover of neighboring plants) and decide that if a competitive crop allows reducing the dose. Recommending the precise required amount of herbicide is achieved using models that account for the interactions among crop and weed species, which survive and persist in the competition after herbicide application.