Eficácia de herbicida associado a palha de babaçu na produtividade da cultura de feijão-caupi

Abstract

The objective of this study was to evaluate the effect of babassu straw as mulch, associated with the herbicide applied in post-emergence, on the efficiency of weed control and on the productivity of cowpea culture. The experiment was implemented during the agricultural year (2017/2018) in an experimental area of the Fazenda School of the State University of Maranhão in the municipality of São Luís -MA. The experimental design was in randomized blocks, in a 4x2 factorial arrangement, with 4 replications, totaling 32 plots. The treatments were two herbicides (bentazon and fluazifop-p-butyl) and four levels of babassu straw on a wet basis (0; 5; 10 and 15 t ha-1). The cowpea cultivar used was BRS Guariba. The herbicides were applied when the bean plants had their second and third fully expanded trifoliolate leaf. Control assessments were carried out at 7, 14, 22 and 37 days after application (DAA) of the herbicides, using a visual scale from 0 to 100%, whose score was attributed to the weed community in general in the plot. At harvest, weeds dry mass and bean production components were evaluated. The weed survey was carried out by means of a 0.5 m x 0.3 m metallic rectangle launched four times in the plots. The plants were separated by species, identified and dried in a 65-70 ° C oven to obtain dry matter. The phytosociological indices obtained were: relative density, relative frequency, relative dominance and the importance value index. The density and dry mass data were transformed into (x + k) and subjected to analysis of variance by the F test, at 5% probability and the means compared by the Tukey test at the 5% probability level. For the percentage of weed control in cowpea culture, it was observed that bentazon (1.6 L ha- 1) and fluazifop-p-butyl (1 L ha-1) applied alone, without the straw of babassu showed good control in the initial period at 7 DAA. The weed community was composed of 22 species, 14 belonging to the eudicotyledonous class and eight monocotyledonous species. As for the productivity of cowpea, fluazifop-p-butyl in the four levels of babassu straw (0; 5; 10 and 15 t ha-1) and Bentazon + 5 t ha-1 babassu straw, obtained the productivity high compared to other treatments. The fluazifop-p-butyl treatment with the application of 15 t ha-1 of babassu straw shows higher productivity of cowpea beans. Bentazon and fluazifop-p-butyl are selective for cowpea culture, however Bentazon causes greater intoxication in the initial period of crop development