Glyphosate hormesis variation in common bean due to nitrogen coverage

Abstract

In order to evaluate the influence of different nitrogen rates on the hormetic effect of glyphosate on common bean crop, proposed to study the combination of nitrogen fertilization in succession to low glyphosate doses. The study was conducted under field conditions at the experimental farm of the State University of São Paulo-UNESP, Ilha Solteira campus, located in the city of Selvíria-MS, Brazil. The experimental design was a randomized block with split plots arranged in four blocks. The plots were composed of four glyphosate doses (0, 7.2, 14.4 and 21.6 g of acid equivalent (AE) ha-1) and the subplots were composed of five nitrogen doses (0, 15, 30, 45 and 60 kg ha-1), with urea as the source. Bean growth was stimulated with a maximum point in the 11 g AE ha-1 sub-dose of glyphosate, however, only in the absence of nitrogen under cover. Leaf N content was higher at the estimated 12 and 11 g AE ha-1 glyphosate doses with 30 and 45 kg ha-1 nitrogen. Hormetic effect on yield was obtained with increments of up to 500 kg ha-1 or 21% at the estimated 10 g AE ha-1 low glyphsate dose. Cooking time was affected by low glyphosate doses, depending on the amount of nitrogen. It was possible to prove the influence of nitrogen on glyphosate hormesis in common bean for dry matter mass, leaf N content, grain yield and cooking time.

Keywords

• phaseolus vulgaris l., nitrogen fertilization, hormetic effect, herbicide, interference