Publicação on-line; 19 ref.; 5 illus.; Summary (En)

ABSTRACT
Background: The pre-emergence herbicides diclosulam and flumioxazin
are used to weed control in soybean. We hypothesized management of
the new emergence of weeds in the early development stages of the
soybean could alter the periods of interference. Thus, the period prior to
interference allows and increases the canopy closure spaces before the
critical period and disfavors the development of weeds inside the
vegetative canopy.
Objective: This study aimed to evaluate whether the period prior to
interference of soybean cultivars was altered due to the application of
residual pre-emergence herbicides.
Methods: Two experiments were conducted with the soybean cultivars
‘NA 5909 RG’ and ‘P95R51’. One day before sowing in the main plots,
the herbicide treatments paraquat (control without residual herbicide),
paraquat+diclosulam, and paraquat+flumioxazin were applied. In the
sub-plots, the increasing periods of coexistence of soybean with weeds
of 0, 7, 14, 21, 28, 35, 42, and 49 days after the emergence of soybean
were allocated.
Results: The control without residual herbicide had the lowest period
prior to interference and the most considerable reductions in grain yield
when compared with residual herbicides in both experiments. The
presence of residual herbicide increased the period prior to interference
because they controlled the initial emergence of the major weeds in the
experimental area.
Conclusions: The use of the herbicides with residual activity diclosulam
and flumioxazin increased the period prior to interference of ‘NA 5909 RG’
and ‘P95R51’ in areas infested mainly with horseweed and radish.

Keywords:
interference periods
pre-emergence
competition
weeds