Revista Brasileira De Herbicidas 2015; 14(1): 1-14

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Influence of glyphosate herbicide in the weed community in the agricultural region of Rio Verde, Goiás

DOI: 10.7824/rbh.v14i1.303

The increasing use of glyphosate in Brazil has increased the selection pressure on species of weeds tolerant and resistant to this herbicide. This study aimed to evaluate the influence of glyphosate use pattern in the population dynamics of weeds in soybeans in thirty-five sampling areas of different properties. These areas were classified as to the number of applications and equivalent amount of glyphosate acid. We used the square-inventory method in thirty-five sampling areas in the 2012/2013 harvest. The structural parameters relative frequency, abundance and value indicator of individuals number and dry weight of shoot were calculated. The graphical representation of the differences of the floristic composition was performed by the non-metric multidimensional scaling technique, with distances of Sorensen. The multi response permutation procedures test was used to test hypotheses of differences in floristic composition. The occurrence of typical species of each treatment was evaluated by the indicator value using the Monte Carlo test (p<0,05). The floristic composition of the number of plants differ between areas using average standards of glyphosate (six applications or 6001 to 8000 g ha-1 of acid equivalent) compared to very low standard areas (four or five applications or 2000 to 4000 g ha-1 of a.i.). The Gnaphalium coarctatum, Eugenia sp., Rumex acetosella and Spermacoce latifolia, Digitaria horizontalis, Urochloa decumbens, Panicum maximum, Gossypum hirsutum and Indigofera hirsuta species showed significant indicator value of environments with different levels of use of glyphosate. Different glyphosate usage patterns exerted influence on the floristic composition of weeds in soybean areas evaluated.