Interactions between Herbicide Dose and Weed Leaf Area Damage Coefficient in a Multiple Weed Species Competition with Maize

Document Type : Research Paper

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Abstract

Weed leaf area damage coefficient (λ) denotes the increase in weed competitiveness per unit increase in its leaf area. Although the variability of this parameter has been confirmed, it was assumed to be constant in many researches. The objective of this study was to determine the interactions between herbicide dose and λ. Field experiments were conducted to determine the relationship between competitive indices of maize, Xanthium strumarium and Amaranthus retroflexus during 2007 and 2008. Five doses of the herbicide nicosulfuron as main factor, and 16 density combinations comprised of 4 densities of A. retroflexus × 4 densities of X. strumarium as sub plots were arranged in a one-replicate split factorial. For A. retroflexus, the λ value was constant. For X. strumarium, the λ value was constant with no herbicide and 0.25 rate of the full dose. With increasing the dose up to half the recommended dose, the λ value increased and again with increasing dose to 0.75 rate, it returned to the level with no herbicide. This relationship was properly described by Gaussian model. Herbicide at half rate probably removed the apical dominance and increased the number of lateral shoots.  Herbicide as an external factor was the most important determinant in the change of X. strumorium canopy shape. Deep understanding of the system behavior, relations and interactions with herbicide applications is of great help in improving the predictive power of weed management models

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Iranian Journal of Weed Science
Volume 9, Issue 2 - Serial Number 2
January 2014
Pages 127-140

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