Occurrence of weeds in Cassava savanna plantations in Roraima

Abstract

-A phyto-sociological survey is the first step to implement integrated weed management in crops. In this study, weed occurrence was evaluated in cassava plantations in the savannah of Roraima in northern Brazil. Harvest was performed randomly 80 times in 10 crops over four seasons (January, February, March, and April 2012). The harvested plants were cut at ground level, sorted out per species, identified, quantified, and weighed on a 0.01 g precision scale. A descriptive analysis was conducted of the phyto-sociological parameters (frequency, density, abundance, total number of individuals per species, relative frequency, relative density, relative abundance and importance value index) for the collected species. A description was also made of the botanical classes, families, species, type of propagation, life cycle, growth habit, total number of species and dry weight ha -1. The community in the surveyed area was considered to have a heterogeneous composition, comprising 27 species. The species presenting the highest density per hectare were Digitaria sanguinalis (210,500), Brachiaria brizantha (111,000), Brachiaria decumbens (86,500) and Brachiaria humidicola (69,000). Digitaria sanguinalis had the highest relative density (28.08), relative abundance (26.16) and importance value index (65,34). Most weeds had herbaceous growth habit.Keywords: Manihot esculenta Crantz, weeds, phytosocial study, savannah, morphological characteristics. RESUMO -O levantamento fitossociológico é o primeiro passo para implantação do manejo integrado das plantas daninhas em culturas. Neste trabalho, objetivou-se avaliar a ocorrência de plantas daninhas em plantios de mandioca na savana de Roraima. As coletas das plantas foram realizadas aleatoriamente 80 vezes em 10 lavouras, em quatro épocas (janeiro, fevereiro, março e abril de 2012). As plantas coletadas foram cortadas ao nível do solo e, depois disso

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

“…Other works conducted with other cultures support this result, such as the ones by Albuquerque et al (2013Albuquerque et al ( , 2014 and Oliveira et al (2015). In order for the agricultural science professional to have the conditions to recommend the proper type of management in an agricultural property, they have to have basic knowledge about various factors, such as propagation methods, life cycle and growth habits, as well as being able to identify weed species, especially at a young stage.…”

“…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).…”