Seletividade do herbicida nicosulfuron para as culturas de milho e arroz / Selectivity of the herbicide nicosulfuron to the crops corn and rice

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The tolerance of the crop corn to the sulfonylurea herbicides, sprayed in post emergence conditions, is variable according to the hybrids that is cultivated. Likewise, it has been observed differential tolerance to nicosulfuron among rice cultivars bred to tolerate the herbicides imazethapyr + imazapic (AHAS-tolerant). Therefore, this research was developed in order to evaluate the selectivity of the herbicide nicosulfuron, sprayed in post emergence conditions, to corn hybrids and AHAS-tolerant rice cultivars. In the experiment with the crop corn, it was studied ten hybrids commercially designated as DKB 370, DKB 990, AG 6020, AG 9040, AS 1551, AS 1572, SWB 585, BX 1149, BM 620 e BM 128, being the experimental design adopted romdomized completely blocks, with five treatments and four replications. The treatments used in g a.i. ha-1 were: nicosulfuron + atrazine at 20 + 1,500; nicosulfuron + atrazine at 40 + 3,000; nicosulfuron at 50; nicosulfuron at 60, as well as a check weed free, sprayed in the phenological stage of four expanded leaves (V4). The hybrids that were tolerant to all treatments, with no yield reduction, were DKB 370, AG 9040, AS 1551 e BM 620. The treatments of nicosulfuron in mixture with atrazine at the rates of 20 + 1,500 e 40 + 3,000 g ha-1 of i.a. were selective to all hybrids tested. The rates of nicosulfuron at 50 and 60 g a.i. ha-1 were the least selective of the experiment, the hybrids DKB 990, AG 6020, AS 1572, SWB 585, BX 1149 and BM 128 showed yield reduction. For the hybrids AG 6020 and SWB 585 there were diferences in the yield among treatments of nicosulfuron 50 and 60 g a.i. ha-1, indicating low tolerance to nicosulfuron. The tolerance to nicosulfuron of the AHAS-tolerant rice cultivars IRGA 422 CL and Puita CL INTA was tested in another experiment. The treatments were obtained from a factorial design 2 x 8, with two rice cultivars and eight rates of nicosulfuron (0, 6.25, 12.5, 25, 50, 100, 200 and 400 g a.i.ha- 1). Visual observations of phytotoxicity symptoms were evaluated at 15 and 20 days after treatments (DAA) and at 20 DAA it was evaluated the root and shoot length and dry biomass of each cultivar separately. The data were submitted to F test in the analysis of variance followed by the application of non linear regressions log-logistic type. The cultivar IRGA 422 CL tolerated higher rates of nicosulfuron when compared to the cultivar Puita CL Inta.

ASSUNTO(S)

sulfonylurea post-emergence plantas daninhas. arroz herbicidas controle químico zea mayz tolerance milho oryza sativa.

ACESSO AO ARTIGO

Documentos Relacionados