Current interest in site-specific weed control regarding to weed spatial variability is currently increasing, when economic, and environmental aspects are considered. But since only a few studies on chemical control efficacy have been conducted until now, a field experiment was developed to evaluate chemical control of weeds applying the site-specific weed control method, as compared to the conventional broadcast application. Four fields of 0.5 ha were chosen and in two of them weeds were surveyed using the systematic grid sampling in a regular grid of 6 x 6 m and counting weeds inside a 0.25 m² quadrat. The two fields where weeds were mapped were used for site-specific application and the other two fields for conventional broadcast application. The quadrat count was done before and after the chemical control in the same location near the stacks. Two label rates were used of the herbicide commercial mixture of fluazifop butyl (125 g L¹) plus fomesafen (250 g L-1), applying 1.0 L ha-1 of the herbicide mixture at sites under 50 weed seedlings m-2 and 2.0 L ha-1 of the same tank mixture at sites above 50 seedlings m-2. Compared to broadcast application, site-specific application saved 18% in one field and 44% in the other. Both had satisfactory chemical control with 55% and 77% of the fields weed free, at very low densities. Thus, this research showed that high herbicide savings are possible, maintaining the efficacy of chemical control using the site-specific herbicide weed management and, consequently, reducing the environmental impact of the broadcast application of herbicides.
mapping; precision farming; spatial variability
