Modeling of imazethapyr dose and velvetleaf (Abutilon theophrasti medik) density interaction on red bean (Phaseolus calcaratus L.) and velvetleaf competition

Modeling of imazethapyr dose and velvetleaf (abutilon theophrasti density interaction on red bean (phaseolus competition. Abstract: Background: Red bean ( Phaseolus calcaratus L.) is cultivated as an economic crop in the Mazandaran Province, Iran. Velvetleaf ( Abutilon theophrasti Medik.) competes severely with red bean growth and reduces yield. Imazethapyr is a selective herbicide recommended for management of grasses and dicotyledonous weeds in different crops including beans. Objectives : This research was conducted to develop an empirical model of red bean yield that incorporates the dose-responses of imazethapyr and velvetleaf densities. Methods : Modeling of imazethapyr herbicide dose on red bean and velvetleaf competition was conducted using four levels of velvetleaf densities and five dosages of imazethapyr arranged in a factorial design. Results : Velvetleaf competitiveness decreased with the increasing imazethapyr dose represented by the standard dose-response curve. A model was improved to composing the dose-response standard curve with the rectangular hyperbola equation. This model estimated red bean economic yield under velvetleaf-free conditions, weed competitivity with no-herbicide application, and the imazethapyr dosage needed to decrease velvetleaf competitiveness about 50%. Imazethapyr at the 0.66 L ha -1 dose was sufficient to control the highest density (12 plants m -2 ) of velvetleaf. Conclusions : Information gained from this study will be important in evaluating economic and environmental terms.