EFFECTS ON GROWTH AND YIELD OF SOYBEANS FROM INTERACTIONS OF SEQUENTIAL HERBICIDE APPLICATIONS
Abstract
Field and greenhouse studies were conducted in two years to evaluate the effects of several pre-plant incorporated and postemergent herbicides applied alone and in sequence upon growth parameters of soybeans {Glycine max (L.) Merr. 'Amsoy 71'}. In general, the greenhouse and field data supported each other. All PPI treatments oversprayed with the postemergent 2,4-DB reduced yield when compared with the PPI's alone. All yield reductions were additive effects, except bifenox at 1.12 kg/ha plus 2,4-DB and vernolate at 3.36 kg/ha plus 2,4-DB. A significant reduction in pods dry weight at thirty-eight days after planting did not correlate with the yields (ninety-eight days later), although all significant yield reductions were preceded by significant reductions in pods dry weight. Bifenox at 0.56 kg/ha oversprayed with acifluorfen at 0.56 kg/ha increased leaf area, leaf dry weight support tissue dry weight, and yield (antagonistic effects). Of the postemergent treatments, bentazon gave the least interaction showing only significant decrease in leaf area and support tissue dry weight with the PPI treatments of vernolate at 3.36 and 5.04 kg/ha; at 5.04 kg/ha it also significantly decreased pods dry weight. After bentazon, came acifluorfen followed by dinoseb + naptalam with no significant yield reduction. Dinoseb + naptalam significantly reduced several parameters including pods dry weight and leaf area when applied over all PPI treatments at the two highest rates. Acifluorfen on the other hand only significantly reduced the growth parameters, other than leaf area, when applied over vernolate at 3.36 and 5.04 kg/ha. The greenhouse results indicated that 2,4-DB applied at 1-trifoliate stage of soybeans reduced several growth parameters when compared with 2,4-DB applied ten days later (3-trifoliate). Vernolate at 3.36 and 5.04 kg/ha reduced chloroform-soluble extraction of the soybean leaves, under field and greenhouse condictions.
Degree
Ph.D.
Subject Area
Botany
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