Levantamento fitossociológico de plantas daninhas em treze áreas experimentais do CCAA, UFMA, Campus IV

ABSTRACT Weeds are those plants that spontaneously emerge in agricultural ecosystems and can cause a series of obstacles. The degree of interference of these plants in agricultural crops depends on the weed community, factors related to the culture, environment and period of coexistence. Men himself can be responsible for the evolution of these plants, since germination and establishment of weeds can be influenced by soil management. The phytosociological survey consists of the first stage of an adequate weed management in an agricultural crop, an essential condition for the definition of more efficient and economic management strategies. The objective of this study was to conduct a phytosociological survey of weeds present in experimental areas with different management histories. The survey was carried out in thirteen experimental areas at the Universidade Federal do Maranhao, Campus IV, Chapadinha (MA), during the dry season of 2018 and the rainy season of 2019. The inventory square method was used (0,5 x 0,5 m), in a regular matrix 4 x 5, in a total of 20 samples per area. Weeds were quantified, identified and measured in height and diameter. The phytosociological indexes comprised frequencies, densities and abundances, absolute and relative, and the index of importance value (IVI), in the evaluation of similarity the Sorensen Similarity Index (IS) was used. In the dry season, 66 species were found, distributed in 20 families, a total of 2.336 individuals collected. Turneraceae, Malvaceae and Poaceae families were distinguished, with Turnera subulata, Waltheria indica and Cenchrus echinatus and Brachiaria sp. In the rainy season, 103 species were identified in 23 families, with a total of 6.460 individuals. The most important families were Turneraceae, Malvaceae, Poaceae, Rubiaceae, Fabaceae and Cyperaceae, with emphasis on Turnera subulata, Waltheria indica, Richardi brasiliensis and Mimosa sp. and Cyperus rotundus. The similarity between the weed communities was strongly influenced by the adopted management, maintaining average for morphologically similar cultures.