Prickly sida (Sida spinosa L.) and spurge (Euphorbia hyssopifolia L.) response to wide row and ultra narrow row cotton (Gossypium hirsutum L.) management systems

A 4 year field study was conducted from 1998 to 2001 to evaluate the response of prickly sida ( Sida spinosa L.) and hyssop spurge ( Euphorbia hyssopifolia L.) growing in either ultra narrow row (UNR) or wide row (WR) cotton ( Gossypium hirsutum L.) management systems. Weeds surviving pre- and postemergence herbicide treatments were harvested just prior to defoliation and the morphological characteristics were compared. Prickly sida growth was significantly reduced with regard to the number of main stem nodes, primary, secondary and tertiary branching, number of seed capsules produced and dry weight under UNR compared with WR. However, plant height was not affected by the management system. Spurge growth was significantly reduced with regard to branching and fresh weight but not height. These results show that UNR might suppress weed development by reducing vegetative and reproductive growth of prickly sida and vegetative growth of spurge. The reduction in seed and seed capsule production of prickly sida is likely to reduce its reproductive potential and also diminish the subsequent seed rain and soil seed bank reserves. Thus, a potential benefit of UNR cotton management systems might be to reduce the competitive ability of weeds and decrease seed production.