Ocorrência de espécies daninhas em função de sucessões de cultivo

Abstract

RESUMO -Objetivou-se neste trabalho avaliar a composição da comunidade infestante na cultura da soja, em função de sucessões de culturas por distintos períodos (uma ou três safras consecutivas). O ensaio foi instalado em campo na Embrapa Agropecuária Oeste, Dourados, MS. Foram avaliados cinco tratamentos de outono-inverno com histórico de uma ou três safras de implantação: milho solteiro -90 cm entrelinhas; milho solteiro -45 cm entrelinhas; consórcio milho + Brachiaria ruziziensis; Brachiaria ruziziensis solteira; e feijão-caupi. No final do mês de setembro de 2011, as áreas foram dessecadas com glyphosate para semeadura da soja; 30 dias após a dessecação, foram realizadas as avaliações. A caracterização fitossociológica das plantas daninhas estimou a abundância, a frequência, a dominância e o índice de valor de importância de cada espécie em cada área. As áreas foram ainda intraanalisadas quanto à diversidade de espécies, pelos índices de Simpson e Shannon-Weiner, e intercaracterizadas pela matriz de similaridade de Jaccard, pelo método UPGMA. O cultivo da soja deve ser seguido pela semeadura de espécie que proporcione elevada quantidade de palha residual na entressafra, com distribuição uniforme na superfície do solo. Essa palhada deve ser formada por resíduos de plantas com elevada relação C/N. Neste estudo, os sistemas de consórcio milho+braquiária, ou mesmo braquiária solteira, resultaram em menor nível de infestação por plantas daninhas em áreas de sucessão à soja, ao longo do tempo de utilização.Palavras-chave: safrinha, fitossociologia, diversidade, similaridade.ABSTRACT -This study aimed to evaluate the composition of weed communities in the soybean culture under cultivation of distinct commercial crops, grown for one or three subsequent years, without crop rotation. The experiment was installed under field conditions at Western Agriculture Embrapa, Dourados, Brazil. Five fall-winter treatments, planted over one or three subsequent years, were evaluated: corn planted 90 cm between rows; corn planted 45 cm between rows, intercropped corn + Brachiaria ruziziensis, B. ruziziensis alone, and Cowpea. At the end of September 2011, all areas were desiccated with glyphosate, with evaluation being carried out 30 days after the first desiccation. The phyto-sociological characterization of the weed communities was based on abundance, frequency, dominance, and importance index of each species in the community. Areas were also intra-characterized by the diversity coefficients of Simpson and Shannon-Weiner and inter-characterized by the similarity matrix of Jaccard, through cluster analysis by the UPGMA method. Soybean sowing should be followed by sowing a species which allows accumulation of high amounts of residual dry mass on the soil surface, and this dry mass should present high C/N ratio. At this study, the intercropped corn + B. ruziziensis, or even B. ruziziensis alone, planted following soybean, allowed lower infestation levels by weed species after three years of cultivation.

Space variability of phenological indicators of common bean crop

“…The other regions ranged between medium and low dry matter production. The value of this attribute studied, according to Concenço et al, (2013) indicates that the planted crop should be followed by sowing of species that provide high amount of residual dry matter in the off-season, with uniform distribution on the soil surface. Moreover, in recent years there has been a prolonged period of drought over the sowing of soybeans in the Cerrado region, causing problems of germination and development of this crop.…”

<b>Phytosociology of weed in the southwestern Goiás region

“…This variable was strong enough to promote significance because this species was observed in only 13% of the samples in maize areas. In general, traditional cultures deficient in soil plant cover such as maize result in increased presence of weeds (Concenço, Ceccon, Correia, Leite, & Alves, 2013). Even though maize can produce significant amounts of dry mass, the coverage provided by this culture may be deficient because the biomass is significantly concentrated in stems with few leaves covering the soil to prevent germination and seedling growth (Andrade, 1995).…”

Interferência de plantas daninhas na cultura do sorgo sacarino

“…from V 9 , suggesting a later emergence of this species, which reflected directly in the IV (%). High IV (%) values indicate plants better adapted to the environment evaluated, presenting large number of individuals and good distribution in the area, rapid early growth, favoring the use of photosynthetically active radiation and consequently contributing to the suppression of neighboring species (Concenço et al, 2013b). Species of the genus Commelina are annual plants, with semi-prostate growth habit, and propagation by seed and stem rooting (Lorenzi, 2008).…”