The objective of this study was to evaluate the initial competitive ability of canola hybrids against Brassicaceae and Poaceae species in terms of root and shoot resources. Two experiments were conducted in greenhouse, in a completely randomized design with four replications. The treatments consisted of interference conditions by root + shoot interference (root+shoot) and shoot interference (Light); and Brassicaceae and Poaceae weeds competing with hybrid of canola (Hyola 61 and Diamond) with different traits for competitiveness. The plant height, root length, dry matter of shoot and root, number of leaves and leaf area were evaluated. Data were compared using orthogonal contrasts. The turnip and volunteer canola reduced root development of the Hyola 61 in root + shoot interference, and among the Brassicaceas weeds, turnip caused greater losses. Brassicaceas weeds caused largest reductions in Diamond’s hybrid growth compared to Poaceae, mainly under light interference. Brassicaceas and Poaceae weeds cause similar damage to Hyola 61 hybrid, and the injury is higher for root +shoot interference. The black oat induce shoot growth in the Diamond hybrid under shoot interference, while among the Brassicaceae weed species, there were no differences.

Volunteer corn can become a weed where beans are grown in succession to corn and there is little information on yield losses and economic threshold for volunteer corn on bean. The objective was to evaluate the effect of volunteer corn density and emergence timing on bean yield and economic threshold. The volunteer corn was planting at 0, 0.5, 1, 2, 4, 8 and 12 plants m -2 in two relatives emergence timing on bean crop (at bean emergence and seven days after bean emergence). The competitive effects on bean yield was high when volunteer corn emerge at bean emergence than late emergence. When volunteer corn emerges at early timing, the yield bean was reduced between 19.6 and 35.5% at one volunteer corn m -2 , while for late emergence of volunteer corn, the yield losses ranged from 11.1 and 19.7%. The bean yield had highest impact on economic threshold, indicating low corn densities to justify the control. The increase of grain yield, bean price, herbicide efficiency and reduction in control costs decreased the economic threshold of volunteer corn on bean. The volunteer corn shows high interference potential on bean. The early timing emergence and increase of density of volunteer corn growing with bean causes highest yield losses. Perda de rendimento de feijão em resposta ao milho voluntário RESUMO: O milho voluntário se tornou uma planta daninha no feijão em sucessão ao milho e há poucas informações sobre a perda de rendimento e os níveis de danos econômicos desta planta sobre o feijão. O objetivo foi avaliar os efeitos da densidade e época de emergência do milho voluntário sobre o rendimento e nível de dano econômico no feijão. O milho voluntário foi semeado em 0, 0.5, 1, 2, 4, 8 e 12 plantas m -2 em duas épocas de emergência relativas ao feijão (na emergência do feijão e sete dias após emergência do feijão). A emergência precoce do milho voluntário causa maiores efeitos negativos sobre o feijão comparado com emergência tardia. A emergência precoce de uma planta de milho voluntário reduz entre 19,6 a 35,5% do rendimento do feijão, enquanto que a emergência tardia reduz entre 11,1 a 19,7%. A produtividade do feijão teve alto impacto sobre o nível de dano econômico, indicando que o controle se justifica em baixas densidades. Incrementos em rendimento de grãos, preço do feijão, eficiência do herbicida e redução nos custos de controle, diminuíram os níveis de dano do milho voluntário sobre o feijão. O milho voluntário apresenta alto potencial de interferência sobre o feijão. A emergência precoce do milho voluntário e o aumento da densidade causam altas perdas no rendimento da cultura. Palavras-chave: nível de dano; época de emergência; interferência; Phaseolus vulgaris; Zea maysBean yield loss in response to volunteer corn Rev. Bras.

This study evaluated the relative competitiveness of two common bean cultivars in coexistence with volunteer corn emerging at different times in different proportions of plants in the association. Firstly, for both beans and volunteer corn, the plant population was determined in which the final production of dry biomass becomes constant (24 plants pot-1). A completely randomized experiment design, with five replicates, was carried out in a 2×2×5 factorial scheme, involving two common bean cultivars (IPR Gralha and Fepagro Triunfo), two emergence times of volunteer corn plants (-7 and 0 days in relation to beans) and five proportions of plants in the association (100:0, 75:25, 50:50, 25:75 and 0:100). At 35 days after bean emergence, measurements of plant height, leaf area and dry biomass of the aerial part of both species were measured. The competitiveness analysis was evaluated through diagrams applied to substitutive experiments and the use of relative competitiveness indices. The height of bean cultivars is reduced when volunteer corn emerges at the highest proportions and in advance. Early emergence of volunteer corn reduces leaf area from both bean cultivars while simultaneous emergence only reduces the leaf area of Triunfo. The dry matter biomass is lowered, due to the competition of the corn emerged before the bean, and the cultivar Gralha is more tolerant. In this way, the importance of the bean sowing in an area free from infestation of volunteer corn plants is verified.

A cultura de aveia-preta (Avena strigosa Schreb) é uma das principais alternativas para o cultivo durante o inverno. A qualidade fisiológica da semente pode interferir na uniformidade, velocidade e a porcentagem de emergência em campo, além de apresentar reflexos sobre a população final. O objetivo do trabalho foi avaliar a qualidade fisiológica de sementes de aveia-preta produzida na safra 2014/2014, proveniente de diferentes unidades de produção localizadas na região Nordeste, Noroeste e Centro Ocidental do RS. A qualidade das sementes foi avaliada através dos testes de germinação, primeira contagem da germinação, índice de velocidade de emergência, emergência em casa de vegetação aos vinte e um dias, desempenho de plântula, massa verde e seca de plântula em laboratório e em casa de vegetação, envelhecimento acelerado, teste de frio, condutividade elétrica. Os tratamentos foram constituídos por 36 lotes de sementes de aveia-preta. Os resultados permitiram concluir que 58,34% dos lotes de aveia-preta apresentaram germinação abaixo do mínimo exigido. Sementes mais vigorosas apresentaram maior desenvolvimento e maior produção de massa. Lotes que expressaram menor percentual de germinação e vigor apresentaram retardamento e desuniformidade de emergência. Palavras-chave:Avena strigosa, germinação, vigor, potencial fisiológico. Physiological quality of black oats seeds (Avena strigosa Schreb) from differentRegions of Rio Grande do Sul. Black oats (Avena strigosa Schreb) are one of the main alternatives for growing during winter. Physiological quality of the seed can interfere with the uniformity, speed and percentage of emergence in the field, besides showing reflexes on the final population. The objective of this work was to evaluate the physiological quality of black oat seeds produced in the 2014/2014 harvest, from different production units located in the Northeast, Northwest and Western Central regions of Rio Grande do Sul, Brazil. Seed quality was evaluated through germination tests, first germination count, emergency speed index, greenhouse emergence at twenty -one days, seedling performance, green mass and seedling dry matter in laboratory and at home Vegetation, accelerated aging, cold test, electrical conductivity. The treatments consisted of 36 lots of black oat seeds. The results obtained allowed to conclude that 58.34% of the lots of black oats presented germination below the minimum required. More vigorous seeds showed higher seedling development and higher mass production. Lots that expressed lower percentage of germination and vigor presented emergency retardation and unevenness.