Composição florística, fitossociologia e diversidade de plantas daninhas no cultivo do coentro (Coriandrum sativum L.) nos municípios de Bacabal e São Luís Gonzaga do Maranhão, estado do Maranhão.

Abstract

Weeds compete with coriander (Coriandrum sativum L.) for water, nutrients, space, and solar radiation, causing drastic drops in production. In addition, many species have allelopathic mechanisms that affect the germination and growth of other species associated with them. However, little is known about the weed species that occur in cilantro cultivation in Maranhão, therefore, knowledge about floristic composition, phytosociology and diversity of weed communities that occur in cilantro cultivation is crucial to support farmers in the application of control methods. Thus, the present work aimed to evaluate the floristic composition, analyze the phytosociology and calculate the floristic diversity of the weed communities that occur in four areas, two of them in vegetable production centers, Areal and Catucá, located in the municipality of Bacabal, and two in family vegetable gardens, in the rural communities of Centro da Josina and Coheb, located in the municipality of São Luís Gonzaga do Maranhão, both municipalities belonging to the microregion of Médio Mearim, state of Maranhão. The survey of species was carried out by the inventory frame method, with 30 collections in each crop area, totaling 120 weed samples throughout the study. The phytosociological parameters evaluated were the absolute and relative values of density, frequency and abundance, besides the value of importance of each species. Floristic diversity was assessed by calculating the Shannon Diversity Index (H'). A total of 6,727 individuals were recorded, distributed among 54 species and 24 families. The three families with the highest species richness were Poaceae (n = 7), Asteraceae (n = 6) and Fabaceae (n = 5). In Areal we found 29 weed species, in Catucá there were also 29, in Centro da Josina, 27 and in Coheb, 32 species. Based on the value of importance, the species that stood out were Portulaca oleracea, Cyperus iria and Eleusine indica in Areal, Cyperus iria, Eleusine indica and Synedrella nodiflora in Catucá, Phyllanthus niruri, Amaranthus lividus and Ludwigia octovalvis in Centro da Josina, and Phyllanthus niruri, Hedyotis corymbosa and Eleusine indica in Coheb. These species require more attention when proposing control methods. The Catucá Production Pole showed the highest floristic diversity (H' = 2.48 nats ind-1).