Phytosociology in agricultural areas submitted to distinct wintercropping management

Abstract

-Studies related to weed dynamics are essential for agricultural sustainability in tropical soils, as their interference can cause significant yield losses, especially in crops with lower competitive ability. This study aimed to assess the composition of weed communities in the third cropping season in areas submitted to distinct wintercroppings for two consecutive years. Evaluations were made in terms of species composition, level of infestation, and severity of occurrence of each weed species in relation to the others within the same area. The wintercropping management systems were: (1) Brachiaria ruziziensis; (2) corn intercropped with B. ruziziensis; (3) corn and (4) cowpea. Plant communities under these wintercrop systems were evaluated in the third year in terms of relative frequency, relative dominance, relative abundance and importance index for each species. Areas were also compared in terms of species composition by the Sørensen´s similarity coefficient. Two years of distinct wintercrop managements were not enough to cause a significant shift in terms of weed composition and severity in a given area. There is also evidence that some weed species are more favored by specific crops, although the causes of this selective behavior are not fully explored in this article. The presence of B. ruziziensis, either alone or intercropped with corn, resulted in lower similarity coefficients when compared to areas where this species was not present. It is suggested that several mechanisms briefly discussed may be involved in the impact of the presence of B. ruziziensis on the weed community.Keywords: weeds, population dynamics, allelopathy, crop rotation, light quality.RESUMO -Estudos relacionados à dinâmica de plantas daninhas são essenciais para a sustentabilidade da agricultura em solos tropicais, uma vez que a interferência pode causar perdas significativas na produção, especialmente em culturas com baixa capacidade competitiva. Objetivou-se com este estudo avaliar a comunidade infestante em áreas submetidas a distintos manejos de inverno nos dois anos anteriores, em termos de composição da flora infestante, do nível de infestação e da severidade da ocorrência de cada espécie daninha, em relação às demais, na mesma área. Os manejos de inverno avaliados foram: (1) Brachiaria ruziziensis, (2) milho em consórcio com B. ruziziensis, (3) milho e (4) feijão-caupi. As comunidades de plantas daninhas nesses sistemas de manejo foram avaliadas em termos de frequência relativa, abundância relativa e dominância relativa, e o índice de valor de importância foi calculado para cada espécie em cada área estudada. As áreas também foram comparadas em termos de composição de espécies, pelo coeficiente de similaridade de Sørensen. Dois anos de manejo distinto na área não são suficientes para ocasionar alterações significativas em termos de composição e severidade de espécies em uma dada área. Há evidência de que algumas espécies daninhas são mais favorecidas pela presença de determinada cultura, embora as causas dessa sele...

Survival and Development of Fall Armyworm (Lepidoptera: Noctuidae) in Weeds During the Off-Season

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Phytosociological surveys: tools for weed science?

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“…The following data were extracted from the raw tables of Concenço et al (2012), supplied as an example (Table 3). Example from raw data of Concenço et al (2012). NOTE: area crossings indicate number of species common to both areas.…”

The role of glyphosate-resistant weeds and starvation on biological, reproductive, and preference parameters of Chrysodeixis includens (Lepidoptera: Noctuidae)

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