This study aimed to determine weed interference periods in semi-erect and semi-prostrate cowpea cultivars. Two simultaneous experiments were conducted with the cowpea cultivars BRS Guariba (semi-erect) and BRS Aracê (semi-prostrate). The experimental design was a randomized block design with four replications in a 7 × 2 factorial scheme, seven periods × two weed management (control and coexistence). Control and coexistence periods consisted of 0, 0-8, 0-16, 0-24, 0-32, 0-45, and 0-60 days after emergence (DAE) for the semi-erect cultivar and 0, 0-8, 0-16, 0-24, 0-32, 0-45, and 0-64 DAE for the semi-prostrate cultivar. Competition throughout the cycle reduced productivity by up to 39.81% for BRS Guariba and 37.27% for BRS Aracê. The cultivars BRS Guariba and BRS Aracê presented critical period of interference prevention of 9 to 41 DAE and 15 to 32 DAE, respectively. The semi-prostrate cultivar BRS Aracê was more competitive with weeds, requiring a shorter control period to express maximum productivity.
The goal of this study was to evaluate the occurrence of weeds after soybean harvest in rotational systems of no-till and conventional tillage in the savannah of Roraima, Brazil. Two simultaneous experiments were conducted in adjacent areas, the first one with no-till soil management system and the second one with the conventional system, with crop rotations for five agricultural years: pearlmillet (2007/2008), soybean (2008/2009), maize (2009/2010), cowpea with maize (2010/2011), soybean (2011/2012) and maize (2012/2013). The used experimental design was the randomized block one with 28 plots, sized 3 x 15 m (45 m2) distributed in 4 blocks. In May 2010, the combined sowing of cowpea and maize was performed, and later, during the same month of 2011 soybean was sown. Thirty days after harvesting, weeds were collected. The botanical classification of species was performed by classes, families, scientific and popular names, as well as comparisons with specialized bibliographies. The evaluated phyto-sociological parameters were: relative frequency (FRR), relative density (DRR), dominance (Do), importance value index (IVI), Sorensen’s similarity index (SI), numbers of individuals (ha-1) and dry mass (%). Among the 37 species found in both planting systems, 60% belonged to the Liliopsida class; Fabaceae and Malvaceae stood out. However, Poaceae, belonging to the Magnoliopsida class, had the highest number of species in both systems. Most weed species were common in both systems.
Sistemas de manejos das plantas daninhas, utilizando diferentes estratégias de controle, podem alterar a dinâmica populacional das plantas e favorecer o controle de algumas espécies. Objetivou-se com esse trabalho avaliar a ocorrência de plantas daninhas antes e após cultivo de feijão-caupi, em plantio direto, sob quatro formas de manejo da vegetação natural (sem roçada, com roçada, uso de fogo e dessecação com glyphosate) em área da savana Amazônica no estado de Roraima. As avaliações foram realizadas mediante a aplicação do método do quadrado inventário. As plantas daninhas situadas nas áreas amostradas foram cortadas rente ao solo, identificadas e quantificadas. Os parâmetros fitossociológicos analisados foram: frequência relativa, densidade relativa, abundância relativa, índice de valor de importância e índice de similaridade. As principais famílias identificadas foram Cyperaceae, Poaceae e Fabaceae. As formas de manejo da vegetação natural da savana de Roraima para o cultivo do feijão-caupi favoreceram a emergência de 10 espécies de um total de 29. O manejo com o herbicida glyphosate proporcionou o desenvolvimento das espécies Digitaria insularis e Hynchelitrum repens e o controle de 12 espécies, entre elas o Trachypogon plumosus, importante forrageira da região em estudo. O manejo da vegetação natural com o fogo favoreceu o surgimento da espécie Desmodium tortuosum. O manejo com glyphosate promoveu alterações na comunidade infestante de plantas daninhas, nesse foi observado os menores índices de similaridade entre os sistemas de manejo avaliados.Palavras-chave: fitossociologia; Vigna unguiculata; vegetação natural; manejo com fogo. OCCURRENCE OF WEEDS IN COWPEA CULTURE UNDER FOUR HANDLES IN THE WESTERN AMAZON ABSTRACT: Weed management systems, using different control strategies, can change the population dynamics of plants and favor the control of some species.The objective of this work was to evaluate the occurrence of weeds before and after cowpea cultivation under no-tillage under four forms of natural vegetation management (no-till, no-till, use of fire and glyphosate desiccation) in an area of savannah of Roraima. Evaluations were performed by applying the inventory square method. Weeds located in the sampled areas were sectioned close to the ground, identified and quantified. The phytosociological parameters analyzed were: relative frequency, relative density, relative abundance, importance value index and similarity index. The main families identified were Cyperaceae, Poaceae and Fabaceae. The management of the natural vegetation of the Roraima savanna for cowpea cultivation favored the emergence of 10 species out of 29. Management with the herbicide glyphosate provided the appearance of the species Digitaria insularis and Hynchelitrum repens and the control of 12 species, including the Trachypogon plumosus, an important savanna forage. The management of natural vegetation with fire favored the emergence of the species Desmodium tortuosum. Glyphosate management caused changes in the weed community, which showed the lowest similarity indexes between the evaluated management systems.Keywords: phytosociology; Vigna unguiculata; natural vegetation; fire management.
This study has aimed to diagnose and compare the predominant weed species in cowpea crop in the Amazon region and to evaluate the effectiveness of herbicides applied in pre-emergence. The weed sampling was obtained before planting, the cowpea cultivar was BRS Aracê, by collecting all the plants present within a 0.25 m² hollow frame, randomly thrown 40 times in experimental area to calculate the phytosociological indices. The herbicide efficiency experiment was conducted in a randomized block design with four replications, in time subdivided plot model. Treatments were applied one day after crop planting, their doses (g/ha ai) were: metribuzin (360), sulfentrazone (600), S-metolachlor (1200), pendimethalin (750), oxadiazon (1000), alachlor (2400), metribuzin + pendimethalin (360 + 750), metribuzin + alachlor (360 + 2400), manual weeding and weedy check. The evaluations of weed control were done at 21, 28 and 35 DAP. The most important weed in phytosociology was Tridax procumbens. Cultivation of the crop with weeds caused a reduction of more than 66% in crop productivity. The application of the metribuzin herbicide prevented the emergence of all cowpea seedlings while oxadiazon satisfactorily controlled the weeds without affecting the crop yield.
As a control measure against weeds, the use of herbicides is an effective and inexpensive alternative. However, there are no products recommended for the cultivation of cowpea in Brazil, making it necessary to search for alternative solutions. The objective of this study was to evaluate the effect of herbicides applied in the pre- and post-emergence on cowpea nodulation and production under conditions of the Amazonian savannah. Two experiments were carried out in a randomized block design with four replicates, using the cowpea cultivar BRS Aracê subjected to the pre-emergence herbicides: Metribuzin, Sulfentrazone, Smetolachlor, Pendimethalin, Oxadiazon, Alachlor, Metribuzin + Pendimethalin, Metribuzin + Alachlor and Quizalofop-p-ethyl, Bentazon, Fomesafen, Imazethapyr, Imazamox + Bentazon, Quizalofop-p-ethyl + Imazethapyr, Quizalofop-p-ethyl + Imazamox and Quizalofop-p-ethyl + Bentazon, and post-emergence herbicides: Quizalofop-p-ethyl, Bentazon, Fomesafen, Imazethapyr, Imazamox + Bentazon, Quizalofop-p-ethyl + Imazethapyr, Quizalofop-p-ethyl + Imazamox, and Quizalofop-p-ethyl + Bentazon. The number of nodules in each plant, the dry matter of nodules, dry matter of roots and the grain yield were evaluated. According to the results obtained, the management of weeds in pre- or post-emergence according to the herbicide used affects the nodulation and productivity of cowpea under the conditions of the Amazonian savannah. The herbicides Metribuzin in preemergence,and Fomesafen and the mixture of Quizalofop-pethyl + Imazethapyr in post-emergence are not recommended for weed control in cowpea. The application of Oxadiazon, Alachlor, and Pendimethalin in pre-emergence can be considered interesting because they do not inhibit the development of the root system or the nodulation of cowpea which provides agreater grain yield. Regarding weed control strategies at postemergence, the application of the herbicide Imazethapyr and the combination of the herbicides quizalofop-p-ethyl + imazamox, Quizalofop-p-ethyl + Bentazon and Imazamox + Bentazon allow satisfactory levels of grain yield, root system development and nodulation of cowpea.
El frijol caupíes un cultivo importante para la seguridad alimentaria de la población mundial;sin embargo, su producción es afectada constantemente por la interferencia de las malezas. El objetivo de estainvestigación fue determinar el efecto de la interferenciadelasmalezasen diferentes densidades de competencia sobre las características de crecimiento del cultivo. El estudio fue conducido mediante diseño de bloques al azar en arreglofactorial 2x4 para análisis del cultivoy 2x3 paralasmalezas. Fueron estudiadas dos especies de maleza (Cenchrus echinatusy Rottboellia exaltata) y cuatro intensidades de competencia (cero, dos, cuatro y seis individuos por maceta), con cuatro repeticiones. Las evaluaciones fueron realizadas en la etapa de floración del cultivo y las variables medidas fueron área foliar, masa seca de las hojas, del tallo, de la raíz (MSR), de la parte aérea (MSPA), masa seca total y la relación MSR/MSPA. Además, fueron cuantificadas en las malezas la masa seca de la parte aérea (MSPAM) y de la raíz (MSRM). El aumento de la densidad de competencia de las malezas resultó en disminución de los valores de todas las variables analizadasen el cultivo. En las malezas,C. echinatusmostró mayor MSPAM que R.exaltata,aunqueno hubo diferenciasenMSRM. Ambas malezasafectan negativamente elcrecimiento delasplantas de frijol,aunque con C. echinatusel efecto es aún mayor.El efecto de interferencia es mayor a medida que aumenta la densidad de lasmalezas.
Aims: The objective of this work was to evaluate the influence of planting spacing in soybean intercropped with covering species in the Roraima savanna. Study Design: The experimental design was a randomized complete block design with four replications. Place and Duration of Study: The experiments were conducted at Embrapa Roraima, in Campo Experimental Água Boa, municipality of Boa Vista - Roraima state, in 2015 and 2016. Methodology: Plots consisted in the spacing (0.45, 0.55 and 0.65 m) and the subplots were constituted by the cover plant species Urocloa brizantha, Urocloa ruziziensis, Panicum maximum and the treatment without intercropping. The used soybean cultivar was BRS Tracajá in two crops. The following variables had evaluated: plant height, number of grains per pod, number of pods per plant, 100-grain weight, plant dry matter, insertion of the first pod, grain yield, and dry matter of the covering species and of spontaneous vegetation. Results: Cover plants affected the plant height, number of pods per plant, insertion of the first pod, dry matter of cover species and yield of grains in soybean. The spacing did not influence the growth and production of the soybean crop, except positively in the number of pods per plant with the increased of spacing. The interaction of cover plants and spacing affected the weight of 100 grains, the insertion of the first pod and the dry mass of the cover species. Number of grains per pod and the dry mass of the soybean plants were not affected by the cover plants and by the spacing. Conclusion: The U. brizantha species provids the highest production of dry matter intercropped with soybean, however, the yield of the crop decrease. The U. ruziziensis species is the most suitable for the cultivation intercropped with the crop. The used spacing do not influence the productivity.
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