Performance of transgenic soybean cultivars and weed control in function of application times and glyphosate formulations

摘要

This work aimed to evaluate selectivity and yield components of transgenic soybean cultivars and weed control in function of application times and glyphosate formulations. The experiment was carried out at Palma Agriculture Center (CAP/UFPel) during the 2005/2006 growing season and arranged in a randomized complete block design in split-split plots, with four replications. Roundup Ready (RR) soybean cultivars were allocated in the plots (BRS 244RR, MSOY 7979RR and NR, not registered ones); application times (20, 35 and 50 days after emergence) were allocated in the split-plots; and the glyphosate formulations (isopropylamine salt - Roundup Ready® or Roundup Transorb®, ammonium salt - Roundup WG® and potassium salt-Zapp Qi®) at the rate of 720 g a.e. ha-1 and infested ckeck were allocated in the split-split plots. The yield parameters evaluated were culture herbicide phytotoxicity, weed control, number of green beans and grains per plant, grain weight and grain yield. The herbicide glyphosate in the tested formulations was selective to the tested soybean cultivars. In general, the best weed control formulation was Roundup WG®. At the initial development of the culture, herbicide application provided better control of purslane, redroot pigweed, alexandergrass, barnyardgrass and bermudagrass. Grain yield varied among soybean cultivars but it did not differ among the glyphosate formulations, being higher when the application was accomplished at the late stages of culture development.