Dynamics and Spatial Variability of Weeds under Soil Tillage Systems in Forage Sorghum

Mapping and characterization of spatial distribution of weeds by means of precision agriculture, coupled to phytosociological surveys, has been used as a tool for localized control techniques. This study evaluated weed incidence and dynamics, as well as spatial distribution, as a function of soil tillage systems in forage sorghum. The experiment was conducted in Petrolina-PE. The experimental area was prepared with four tillage systems, as follows: no primary tillage, tandem disc harrow plus moldboard plow, disc harrow off-set of 0.61 m and tandem disc harrow plus chisel plow. Data were collected on forage sorghum at 110 days after emergence, in a rectangular area of 20 x 12 m (240 m(2)) with regular mesh of 4 x 3 m, referenced in x and y coordinates. Phytosociological characterization was performed by evaluating weed density, frequency, abundance, dominance, and importance value, as well as spatial variability using geo-statistics with the construction of maps. Cenchrus echinatus presented higher incidence and importance value index. Weed mapping has relevance to the application of control methods, especially when coupled with phytosociological surveys.