Composição florística e estudo fitossociológico de plantas espontâneas e produção do arroz em cobertura morta de palha de babaçu

Abstract

The objective of this study was to analyze the effects of the cover of crushed babassu leaves on the spontaneous vegetation in the cultivation of two rice cultivars in the municipality of Arari-MA. The experiment was conducted in the agricultural years 2016/2017 in a randomized block design, in a factorial scheme with four replications. The treatments were distributed in two levels for the cultivar factor (Comecru and Cambará) and four levels for the babassu straw factor (0 t ha-1, that is, without straw and absence of control of spontaneous plants by weeding, 15, 20, 25 t ha-1), plus two witnesses Additional control of spontaneous plants in the plots of the cultivars comecru and Cambará. Spontaneous plant survey was carried out by means of a metallic rectangle of 0.5 m x 0.3 m released four times, randomly in the plots during seven assessments (20, 30, 40, 50, 60, 70 and 110 days after the emergence of the crop). The plants were separated by species, identified and dried in greenhouse from 65-70 ° C to obtain the dry matter. The phytosociological indices obtained were: relative density, relative frequency, relative dominance and the importance value index. In the cv Comecru in the presence of babassu straw, 23 species of spontaneous plants were identified, distributed in 14 botanical families, three from the Monocotyledons group and 11 from the eudicotiledons; For cultivar Cambará, there were 17 species in 12 families of which, three families of the Monocotyledons Group and nine of the eudicotiledons. The family with the highest species richness in rice cultivars was cyperaceae with four representatives. The spontaneous species with the highest importance in cultivars from 20 to 70 DAE in all straw quantity was Cyperus would have values above 100%; At the harvest, the 110 DAE in cv Comecru in 15, 20 and 25 T ha-1 of straw Cyperus would have had ivi of 32.78%, 52.83% and 31.46%, respectively. In the cv Cambará, the ivi of this species was 62.40%, 56.00% and 120.93% for these quantities of straw. The highest yields of the cultivars were obtained in 25 T ha-1 of straw, 953.91 kg ha-1 for cv comecru and 339.53 kg ha-1 for cv Cambará. The presence of straw and cultivars influence the floristic composition of the spontaneous vegetation in the rice crop, mainly in the largest amount of straw (25 t ha-1) and in the traditional cultivar Comecru. The Monocotyledons Botanical group predominates in all the quantities of straw used whose family of greatest importance is Cyperaceae. The species with the highest value of importance in the two cultivars is C. iria would followed by A. tenella and F. Dicothoma. in 25 t ha-1 of babassu straw There is a higher suppression of spontaneous plants and yield of cultivars. The agronomic characteristics of the cv Comecru Rice favor its competitive potential with spontaneous plants that reflects in higher productivity.