Fitossociologia e características morfológicas de plantas daninhas após cultivo de milho em plantio convencional no cerrado de Roraima.

Abstract

Resumo -A fitossociologia é o estudo florístico e estrutural das espécies vegetais, desempenhando um papel bastante importante para o manejo das Plantas Daninhas. Objetivou-se com este trabalho estudar a fitossociologia e características morfológicas de plantas daninhas após cultivo de milho em plantio convencional no cerrado de Roraima. O trabalho foi realizado em área preparada em sistema de cultivo convencional por cinco anos, sendo a avaliação realizada após cultivo com milho. As coletas foram realizadas quatro meses após a colheita, durante os meses de maio a junho de 2010. Para amostragem, utilizou-se quadrado de ferro, 0,50 x 0,50 m, lançado aleatoriamente oito vezes na área experimental (45 m 2 ). As plantas daninhas foram identificadas e quantificadas por meio do somatório das amostras obtidas pelo lançamento do quadrado. As variáveis avaliadas compreenderam: frequência, densidade, abundância, frequência relativa, densidade relativa, abundância relativa e índice de valor de importância das espécies. Foram, ainda, descritas as classes botânicas, famílias, espécies, tipo de propagação, ciclo de vida e hábito de crescimento. Na área experimental foram identificadas dezenove espécies de plantas daninhas, divididas em nove famílias botânicas, sendo as Fabaceae e Poaceae com maiores ocorrências. Das espécies de plantas daninhas, um percentual de 63,15% pertencem a classe botânica das Dicotiledôneas. A Sida rhombifolia foi à única espécie que foi encontrada em todas as coletas amostrais e Cenchrus echinatus foi a espécie mais abundante. As espécies que apresentaram maior índice de valor de importância, foram: Cenchrus echinatus, Sida rhombifolia, Digitaria sanguinalis e Cyperus rotundus. Palavras-chave -Identificação de plantas infestantes. Estudo florístico e estrutural. Savana de Roraima. Zea mays (L.)Abstract -The Phytosociology is the floristic and structural study playing a very important role for the management of Weeds. The objective of this work was to study the phytosociology of weed after growing corn in conventional tillage in the savanna of Roraima. The phytosociological survey of soil management with crop rotation was conducted four months after the corn harvest in the period of May-June, 2010. For sampling was used an iron square with dimensions of 0.50 x 0.50 m, thrown randomly eight times in each corn plot, with area of 45 m 2 . Weeds were identified and quantified by the sum of two samples per plot. Evaluated variables: frequency, density, abundance, relative frequency, relative density, relative abundance, importance value index, fresh weight and dry weight of the species. Additionally, the botanical classes, families, species, type of propagation, life cycle, growth habit, the total number of species per ha -1 , and dry matter were described. Ninetten weed species were found in the area, separated into nine botanical families, being the Poaceae and Fabaceae with higher occurrences. 63.15% of the weed species belonging to the botanical class of Dicotyledons. Sida rhombifolia was the only spec...

Weed Incidence After Soybean Harvest in No-Till and Conventional Tillage Croprotation Systems in Roraima’s Cerrado

“…In works conducted by Albuquerque et al (2013), while evaluating the incidence of weeds in the maize culture after soybean in Roraima's cerrado, nine families were identified; the highest occurrence belonged to Poaceae, Fabaceae, Malvaceae and Cyperaceae, supporting the results from this research. According to López-Ovejero et al (2016), when the culture before soybean is maize, generally the presence of volunteer maize plants reduces soybean production; however, in the experiment there were practically no volunteer plants from the previous culture (maize).…”

“…Other studies conducted in Roraima's cerrado have confirmed the species number predominance of the Fabaceae family (Cruz et al, 2009;Flores and Rodrigues, 2010;Albuquerque et al, 2013Albuquerque et al, , 2014.…”

“…In each harvesting period, some species stand out because of various factors, among which: species characteristics, climate, seed bank, culture development, control period and adopted planting system (Albuquerque et al, 2013(Albuquerque et al, , 2014.…”

“…In the agronomic point of view, knowing species diversity is essential to understand the dynamics of weeds and agricultural crops. In spite of this importance, few works were published about surveying weeds in this state (Cruz et al, 2009;Albuquerque et al, 2013Albuquerque et al, , 2014Oliveira et al, 2015).…”

“…The number of individuals (ha -1 ) and dry mass (%) were estimated and the propagation type, life cycle and growth habits of weeds were described, according to works conducted by Albuquerque et al (2013Albuquerque et al ( , 2014 and Oliveira et al (2015).…”