Interferência de herbicidas na associação da bactéria diazotrófica Nitrospirillum amazonense e mudas pré-brotadas de cana-de-açúcar

Abstract

The microbial inoculant for sugarcane containing Nitrospirillum amazonense cells is a recent technology and has been adopted in association with pre-sprouted seedlings to sustainably increase the crop's productivity. The objective of this work was to evaluate the sensitivity of the bacterium Nitrospirillum amazonense to imazapic and indaziflam herbicides, as well as the impact of this inoculation and herbicide treatments on pre-sprouted sugarcane seedlings. The “in vitro” sensitivity of the bacterium N. amazonense to herbicides was evaluated using the minimum inhibitory concentration technique (Assay 1). In this trial, 2 herbicides (imazapic - 200 g a.i. ha-1 and indaziflam - 100 g a.i. ha-1) in 5 doses were evaluated. In the second trial, the sensitivity of N. amazonense to imazapic and indaziflam herbicides, applied at commercial doses, in autoclaved soil was evaluated. The bacterial population count was performed using the most likely number technique (McCrady Table). In trial 3, herbicide treatments were evaluated (indaziflam, imazapic, clomazone, tebuthiuron, sulfentrazone, without herbicide), applied in pre-planting of pre-sprouted seedlings of the variety RB 966928, in the presence and absence of the inoculant N. amazonense. According to the results of the tests, the presence of indaziflam did not interfere in the in vitro growth of the bacterium N. amazonense, regardless of the dose. Imazapic caused significant inhibition of bacterial growth only at the 2DC dose. The count of the bacteria N. amazonense in the soil of the treatments that received the application of indaziflam and imazapic, did not differ in relation to the soil without herbicide. The pre-sprouted seedlings of the RB966928 variety showed high sensitivity to the herbicide imazapic, regardless of the inoculation of N. amazonense. The herbicides clomazone, tebuthiuron and sulfentrazone did not interfere in the growth promoting effect of N. amazonense. Inoculation did not change the sensitivity of pre-sprouted seedlings to herbicides. It is concluded that the herbicides evaluated in this study do not interfere in the association of pre-sprouted seedlings of the variety RB966928 with the bacterium N. amazonense, although the selectivity for seedlings is differential among the herbicides.