In the current scenario of resistance of weeds to glyphosate in grain and fiber production systems, imidazolinone-resistant soybean is shown as an option in the rotation of biotechnology events and herbicide action mechanisms through the application of [imazapic+imazapyr]. However, due to its persistence in the soil, the herbicide may harm the subsequent crop. The objective of this work was to evaluate the residual activity of the herbicide [imazapic+imazapyr] applied in pre-emergence in soybean cultivation on cotton in succession. The experimental design was a randomized block design with five replicates, using seven concentrations (0; 6.25; 12.5; 25; 50; 100 and 200%) of the recommended dosage of the herbicide [imazapic+imazapyr] ([78,75+26,25] g ha-1). The cotton was sown 112 days after application of the herbicide with accumulated rainfall of 637 mm during the soybean cycle, totalizing 1,043 mm until the cotton harvest. There was no significant difference for the analyzed variables. It is concluded that the BRS 8482cv soybean cultivar is resistant to double of the recommended dosage ([157.5+52.5] g ha-1) of [imazapic+imazapyr], and its residual soil activity does not affect cotton cv. TMG 42 WS, in the 112 day interval between pre-emergence herbicide application in soybean cultivation and sowing of cotton.

Improved methods of weed control are required to support expansion of large-scale cowpea cultivation in mid-west Brazil. With the aim of testing our hypothesis that the tolerance of cowpea cultivars to sulfentrazone is dose-and genotype-dependent, we assessed the effects of increasing doses (0, 250, 500 and 1,000 g ha-1 of sulfentrazone) on the cultivars BRS Imponente, BRS Novaera, BRS Tumucumaque and BRS Itaim. The phytotoxic effects of sulfentrazone varied according to the dose of herbicide applied, although the symptoms were mild and only observable at the initial stages of development and at the highest dose tested. No statistically significant interactions were detected between cultivars and doses, and there were no significant differences between doses regarding population density, plant height, yield components and grain yield. Our results demonstrate that sulfentrazone is highly selective and can be applied to the studied cultivars without affecting growth or yield.

Residual de herbicidas aplicados no manejo outonal de Conyza spp. sobre a cultura da soja e do milho versão revisada de acordo com a resolução CoPGr 6018 de 2011 Orientador: Prof. Dr. RICARDO VICTORIA FILHO Dissertação apresentada para obtenção do título de Mestre em Ciências. Área de concentração: Fitotecnia