Deriva de glifosato em arroz irrigado e recuperação de plantas mediante adubação nitrogenada

Abstract

Due to crops rotation in rice-land areas and the inclusion of glyphosate-resistant soybean, rice crops are constantly threatened by a drift of glyphosate during aerial applications for burndown treatments in rice and soybean and post emergent management in soybean. Therefore, the present study was conducted to evaluate 1) the potential of glyphosate drift in aerial applications, 2) the yield losses that the glyphosate drift may cause in function of weather conditions interacting with growth stage, and 3) the remediation of rice-crops affected by drift through nitrogen fertilization in the form of urea. Thus, the objectives of this work were: (i) to determine the drift rates in aerial applications (chapter 1); (ii) to evaluate the response of rice plants to simulated glyphosate drift at two sowing times and three growth stages (chapter 2); (iii) remediation of rice crops affected by glyphosate drift through nitrogen fertilization (Chapter 3). Field experiments were carried out to determine the drift rates. An aerial application was made, the xperimental design was completely randomized, evaluating different distances from the application area with use of sentinel rice plants. By comparison of phytotoxicity and severity scale, the drift rates determined were: 14, 13 and 5% of the dose (1920 g i.a. ha-1), corresponding to the distances of 150, 200 and 400 respectively. In the second experiment of sowing times, sowing was replicated at early and late conditions respectively. Simulated drift applications were performed at 4 and 8 leaf stages and panicle differentiation. Sowing time influenced recovery of treated plots at vegetative stage. For the V4 stage, total recovery was observed during the first year at early sowing time, showing no difference in yield among glyphosate rates and the control treatment. On the other hand, plots treated at reproductive stage presented a higher susceptibility. Rates of 5 to 10% were enough to halve the yield. In the remediation experiment, the recommended nitrogen dose corresponds to 60 kg ha-1 in the form of urea.