Phytosociological survey of spontaneous plant communities in a conventional corn crop area in the region of Carajás, Pará, Brazil

The presence of spontaneous plants in agricultural cultivation areas can result in damage to the crop of interest due to competition for natural resources and allelopathy, requiring systematic monitoring for an adequate cultivation management. In this way, the objective was to identify the spontaneous plant communities species in an area of a one-year fallow conventional corn crop in the southeastern of Pará state, in the Brazilian amazon. A phytosociological survey of the plants in the experimental area of the Technological Center of Family Agriculture (CETAF) was carried out, by applying the inventory square method with 1.0 m2, randomly launched twenty times in an area corresponding to 1.1 hectare. The phytosociological parameters analyzed were frequency, relative frequency, density, relative density, abundance, relative abundance and importance value index (IRI). It was found 19 species of spontaneous plants distributed in 11 botanical families, being, Euphorbiaceae (4), Asteraceae (3), Amaranthaceae (2) and Poaceae (2) the most representative in numbers of species sampled. The most important species were Sorghum arundinaceum (IRI = 55.70), Commelina benghalensis (IRI = 47.78) and Synedrella nodiflora (IRI = 42.39). A high diversity of spontaneous plants was verified, emphasizing the need for phytosociological surveys for the definition of integrated control practices in face of the type of cultivation system adopted.