Interference of weeds in ruziziensis grass pastures

The aim of this study was to assess the effect of increasing periods of coexistence of weed plants with Urochloa ruziziensis on the canopy structure and productivity of a pasture already established with this forage species. The experiment was a randomized blocks design with four replications, and treatments consisted of seven increasing periods of coexistence of forage grass with weed plants: 0 (control), 15, 30, 45, 60, 75 and 90 days after regrowth (DAR). The main morpho-structural and productive characteristics of the forage plants were determined at the end of the experimental period (90 DAR). The ratio of the first green leaf height to the tiller height increases, while the leaf to stem ratio diminishes as the period of interaction with the infesting community increases. The number of green leaves per tiller and the tiller height diminishes as the period of coexistence with weed plants increases. The presence of weed plants interferes negatively with all parameters of the grass canopy structure and productivity of a grazing land already established with Urochloa ruziziensis, suggesting that measures of control of the infesting community should be adopted up to 17 days of regrowth of the forage plant.(AU)

Floristic diversification of spreading liverseed grass pasture according to different cutting intensities, obtained by grazing simulation

This study aimed to evaluate the impacts of different forage cutting intensities, obtained by grazing simulation, on the floristic diversity and productivity of a pasture cultivated with spreading liverseed grass. The experiment was set up in a randomized block design, with four replications and treatments arranged in a 5×2 factorial scheme, with five levels of cutting intensity of the simulated grazing (0, 25, 50, 75, and 95% of the forage canopy) associated with two levels of weed coexistence (presence and absence). The evaluations of floristic diversity, number of individuals, and total dry matter of weeds were obtained at 15, 30, 45, 60, and 90 days after grazing simulation (DAGS). All plots were evaluated at the end of the experimental period (90 DAGS) for the amount of dry biomass produced by the pasture. The results showed that higher forage cutting intensities, obtained by grazing simulation, increased the floristic diversity, the number of individuals, and the dry matter accumulated by weeds in a pasture grown with spreading liverseed grass, reducing by up to 56% theproduction of total dry matter of the forage.(AU)

Floristic diversification of spreading liverseed grass pasture according to different cutting intensities, obtained by grazing simulation

This study aimed to evaluate the impacts of different forage cutting intensities, obtained by grazing simulation, on the floristic diversity and productivity of a pasture cultivated with spreading liverseed grass. The experiment was set up in a randomized block design, with four replications and treatments arranged in a 5×2 factorial scheme, with five levels of cutting intensity of the simulated grazing (0, 25, 50, 75, and 95% of the forage canopy) associated with two levels of weed coexistence (presence and absence). The evaluations of floristic diversity, number of individuals, and total dry matter of weeds were obtained at 15, 30, 45, 60, and 90 days after grazing simulation (DAGS). All plots were evaluated at the end of the experimental period (90 DAGS) for the amount of dry biomass produced by the pasture. The results showed that higher forage cutting intensities, obtained by grazing simulation, increased the floristic diversity, the number of individuals, and the dry matter accumulated by weeds in a pasture grown with spreading liverseed grass, reducing by up to 56% theproduction of total dry matter of the forage.

Efeito de subdoses de 2, 4-D sal colina na eficiência quântica do fotossistema II do algodoeiro / Effect of 2, 4-D choline salt subdoses on quantum efficiency of photosystem ii of cotton crop

Efeitos deletérios de herbicidas ao aparato fotoquímico das plantas podem ser quantificados pelo estudo do potencial de rendimento quântico do fotossistema II (Fv/Fm). Por conta disso, objetivou-se avaliar o efeito de subdoses do herbicida 2,4-D formulação sal colina na eficiência quântica do fotossistema II do algodoeiro em diferentes estádios fenológicos. Foi adotado o delineamento experimental inteiramente casualizado, com sete repetições e os tratamentos dispostos por nove frações da dose média de rótulo do herbicida 2,4-D formulação sal colina: 0 (testemunha); 0,4275; 0,855; 1,71; 3,42; 8,55; 17,1; 34,2 e 68,4 g ea ha-1 aplicadas nos estádios fenológicos V4 ou B4 do algodoeiro. As plantas foram avaliadas quanto aos sintomas visuais de injúria e a cinética de emissão da fluorescência máxima da clorofila (Fv/Fm) aos 3, 7 e 14 dias após a aplicação (DAA) do herbicida. Os valores obtidos foram analisados pelo teste F e os efeitos dos tratamentos foram comparados pelo teste de Scott-Knott a 5% de probabilidade. Os dados obtidos de injúria visual e de Fv/Fm também foram submetidos à correlação de Pearson. A correlação entre a injúria visual e a Fv/Fm nos estádios V4 e B4 é negativa e significativa para ambos anos de condução do experimento. A variável Fv/Fm não foi afetada pela aplicação de subdoses inferiores a 3,42 g ea ha-1 de 2,4-D sal colina no estádio V4 e inferiores ...

Deleterious effects of herbicides on the photochemical apparatus of plants can be quantified by studying the quantum yield potential of photosystem II (Fv/Fm). Therefore, the objective of this work was to evaluate the effect of subdoses of the herbicide 2,4-D choline salt formulation on the quantum efficiency of the photosystem II of cotton plantsat different phenological stages. The study adopted a completely randomized experimental design with seven replications, and the treatments consisted of nine fractions of the average rate indicated on the 2,4-D choline salt herbicide label: 0 (control); 0.4275; 0.855; 1.71; 3.42; 8.55; 17.1; 34.2 and 68.4 g ae ha-1applied at phenological stages V4 or B4 of cotton plants. The plants were evaluated for the visual symptoms of injury and the emission kinetics of maximum chlorophyll a (Fv/Fm) fluorescence at 3, 7 and 14 days after application (DAA) of the herbicide. The values obtained were analyzed by the F test and the effects of the treatments were compared by the Scott-Knott test at 5% probability. The data obtained from visual injury and Fv/Fmwere also submitted to Pearson's correlation. The correlation between visual injury and Fv/Fmin the V4 and B4 stages is negative and significant for both years of conducting the experiment. The Fv/Fmvariable was not affected by the application of subdoses lower than 3.42 g aeha-1of 2,4-D saline choline in the V4 stage and below 1.71 g aeha-1in the B4 stage of the cotton plant.

Efeito de subdoses de 2, 4-D sal colina na eficiência quântica do fotossistema II do algodoeiro / Effect of 2, 4-D choline salt subdoses on quantum efficiency of photosystem ii of cotton crop

Efeitos deletérios de herbicidas ao aparato fotoquímico das plantas podem ser quantificados pelo estudo do potencial de rendimento quântico do fotossistema II (Fv/Fm). Por conta disso, objetivou-se avaliar o efeito de subdoses do herbicida 2,4-D formulação sal colina na eficiência quântica do fotossistema II do algodoeiro em diferentes estádios fenológicos. Foi adotado o delineamento experimental inteiramente casualizado, com sete repetições e os tratamentos dispostos por nove frações da dose média de rótulo do herbicida 2,4-D formulação sal colina: 0 (testemunha); 0,4275; 0,855; 1,71; 3,42; 8,55; 17,1; 34,2 e 68,4 g ea ha-1 aplicadas nos estádios fenológicos V4 ou B4 do algodoeiro. As plantas foram avaliadas quanto aos sintomas visuais de injúria e a cinética de emissão da fluorescência máxima da clorofila (Fv/Fm) aos 3, 7 e 14 dias após a aplicação (DAA) do herbicida. Os valores obtidos foram analisados pelo teste F e os efeitos dos tratamentos foram comparados pelo teste de Scott-Knott a 5% de probabilidade. Os dados obtidos de injúria visual e de Fv/Fm também foram submetidos à correlação de Pearson. A correlação entre a injúria visual e a Fv/Fm nos estádios V4 e B4 é negativa e significativa para ambos anos de condução do experimento. A variável Fv/Fm não foi afetada pela aplicação de subdoses inferiores a 3,42 g ea ha-1 de 2,4-D sal colina no estádio V4 e inferiores ...(AU)

Deleterious effects of herbicides on the photochemical apparatus of plants can be quantified by studying the quantum yield potential of photosystem II (Fv/Fm). Therefore, the objective of this work was to evaluate the effect of subdoses of the herbicide 2,4-D choline salt formulation on the quantum efficiency of the photosystem II of cotton plantsat different phenological stages. The study adopted a completely randomized experimental design with seven replications, and the treatments consisted of nine fractions of the average rate indicated on the 2,4-D choline salt herbicide label: 0 (control); 0.4275; 0.855; 1.71; 3.42; 8.55; 17.1; 34.2 and 68.4 g ae ha-1applied at phenological stages V4 or B4 of cotton plants. The plants were evaluated for the visual symptoms of injury and the emission kinetics of maximum chlorophyll a (Fv/Fm) fluorescence at 3, 7 and 14 days after application (DAA) of the herbicide. The values obtained were analyzed by the F test and the effects of the treatments were compared by the Scott-Knott test at 5% probability. The data obtained from visual injury and Fv/Fmwere also submitted to Pearson's correlation. The correlation between visual injury and Fv/Fmin the V4 and B4 stages is negative and significant for both years of conducting the experiment. The Fv/Fmvariable was not affected by the application of subdoses lower than 3.42 g aeha-1of 2,4-D saline choline in the V4 stage and below 1.71 g aeha-1in the B4 stage of the cotton plant.(AU)