Weed Biology and Management

Abstract

The effects of surfactants and simulated rain were investigated on the efficacy of Engame and Roundup Ultramax formulations of glyphosate on johnsongrass (Sorghum halepense L.), prickly sida (Sida spinosa L.) and yellow nutsedge (Cyperus esculentus L.). Flame surfactant provided the greatest enhancement of Engame efficacy and the effect was species-dependent. Flame enhanced the activity of Engame on johnsongrass and yellow nutsedge but not on prickly sida. Engame and Engame plus Flame were more active than Roundup Ultramax on a glyphosate acid-equivalent basis on johnsongrass without rain, and on yellow nutsedge with or without rain. The Engame and Roundup Ultramax activities on johnsongrass were similar with rain, and rain occurring between five and 30 min after treatment diminished their activities to <38% of the control. With the addition of Flame surfactant, Engame activity on johnsongrass increased, such that 50% and 80% of the control were realized, even with rain occurring between five and 15 min after treatment, respectively. Engame and Roundup Ultramax provided better control of prickly sida than of johnsongrass following a rain event. The addition of Flame surfactant to Engame did not enhance the activity on prickly sida. Yellow nutsedge control with Engame and Engame plus Flame was greater than with Roundup Ultramax and rain had little effect on control regardless of the length of the rain-free period. These results demonstrated that the activities of Engame, Engame plus Flame and Roundup Ultramax were species-dependent and surfactant-dependent.

Critical Period of Weed Interference on Soybean (Glycine Max (L) Merrill)

“…The lowest weed dry observed in treatments could be as a result of the effectiveness of the treatments to lower the presence and population of weed on the plots hence the lower dry weight. This is in accordance that controlling the presence of weed, reduces their presence on the field (Buhler and Hartzler, 2004). The higher plant height observed in these treatments could be as a result of the ability of the treatment to reduce the presence of weed on the field, thereby reducing weed-crop competition on the plant which translated into taller plant heights.…”

Narrow-Row Production System for Soybeans in Mississippi Delta

“…Greater soybean yields were attributed to the development of full canopies earlier than those planted at wider spacing (Shibles and Weber, 1966; Taylor et al, 1982; Heatherly et al, 1999) and the rapid canopy closure increases the total amount of solar radiation intercepted by the crop (Ethredge et al, 1989). The more rapid canopy closure of narrow rows also increases weed suppression (Buhler and Hartzler, 2004), reduces soil temperature, and soil evaporation (Hoeft et al, 2000).…”

Integrated pigweed (Amaranthus spp.) management in glufosinate-resistant soybean with a cover crop, narrow row widths, row-crop cultivation, and herbicide program

“…Narrow row width (NRW; i.e., <76 cm) increases soybean tolerance of early-season weeds when compared with wide row spacing (Knezevic et al 2003). Using NRW increases light interception (LI), enhances canopy development by the crop (Elmore 1998;Shibbles and Weber 1966;Yelverton and Coble 1991), and is recognized as a means of weed suppression (Buhler and Hartzler 2004). NRWs have been reported to decrease lateseason waterhemp density in soybean (Schultz et al 2015).…”

“…Row-crop cultivation in soybean is commonly recognized as an integrated weed management practice (Buhler and Hartzler 2004) and when implemented during the critical weed-free period, reduces the impact of weeds on crop yields (Mohler et al 2016;Peters et al 1965). Although capable of providing excellent weed control between rows, row-crop cultivation does not control weeds in the crop row (Jordan et al 1987;VanGessel et al 1998) and is better suited to fields with sparse weed densities (Buhler et al 1992;Dieleman et al 1999).…”