Interferência de capim-camalote em cana-de-açúcar e seletividade de indaziflam e indaziflam + metribuzin aplicados em cana-de-açúcar no sistema MPB
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Data
2016-07-20
Autores
Hijano, Neriane [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A interferência de plantas daninhas em cana-de-açúcar é um fator determinante para a produtividade e qualidade da cultura, destacando dentre essas o capim-camalote (Rottboellia cochichinensis), cuja importância vem crescendo neste setor agrícola. Para o manejo dessas plantas visando minimizar a interferência, o conhecimento dos períodos de interferência de plantas daninhas em cana-de-açúcar possibilita o melhor posicionamento de herbicidas com ação residual. O objetivo da realização deste trabalho foi determinar o período de interferência do capim-camalote em cana-de-açúcar, a densidade crítica de capim-camalote capaz de interferir no desenvolvimento de mudas pré brotadas (MPB) de cana-de-açúcar e após o corte da cana o efeito no rebrote destas mudas e a seletividade do indaziflam e indaziflam + metribuzin em MPB de cana-de-açúcar. Para determinação dos períodos de interferência do capim-camalote em cana-de-açúcar o experimento foi realizado em área comercial, com a cultivar CTC14 plantada em janeiro. Os períodos de convivência ou de controle foram 0-23, 0-37, 0-44, 0-58, 0-72, 0-92, 0-122, 0-240, 0-300, 0-450 dias após o plantio (DAP). Considerando uma tolerância de redução de 5% na produtividade da cana-de-açúcar com interferência predominante de capim-camalote, o período anterior à interferência encontrado foi de 54 dias e o período total de prevenção a interferência foi de 130 dias após o plantio. Houve redução de 26,4% na produtividade quando comparada ausência total de plantas daninhas a presença dessas durante todo o ciclo; o valor do açúcar total recuperável (ATR) diminuiu com o aumento do período de convivência com as plantas daninhas. Para determinação das densidades de R. cochichinensis que interferem no desenvolvimento de mudas pré-brotadas (MPB) de cana-de-açúcar e o efeito das densidades no rebrote das soqueiras, o delineamento utilizado foi em blocos casualizados, com quatro repetições, sendo as populações de capim-camalote de 1; 2; 4; 8 e 16 plantas vaso-1 para ‘RB855156’ e 1; 2; 8 e 16 plantas vaso-1 para ‘CTC14’, mais a cana-de-açúcar na ausência do capim-camalote. Para o capim-camalote, os tratamentos foram compostos pelas densidades, na ausência e na presença da cultura. Aos 25, 55, 85 e 120 dias após o plantio (DAP) das mudas foram avaliados, no colmo principal, a altura, diâmetro, número de folhas e de perfilhos. Aos 120 DAP foram avaliados também o número de folhas totais, área foliar e a massa seca. As plantas foram cortadas rente ao solo e as soqueiras da cana-de-açúcar foram mantidas por mais 90 dias isentas do capim-camalote para avaliação do rebrote. O aumento da população de capim-camalote não interferiu nas características avaliadas do colmo principal, mas desencadeou menor número de perfilhos, de folhas totais, menor área foliar e massa seca de perfilhos. Para a ‘RB855156’ não houve recuperação da soqueira até 90 dias após o corte. A planta daninha apresentou competição intraespecífica nas maiores densidades testadas. O experimento de seletividade foi realizado em quatro partes, utilizando a combinação de duas cultivares de cana-de-açúcar (RB966928 e CTC14), as cultivares de cana-de-açúcar foram plantadas pela técnica MPB, e dois herbicidas (indaziflam e indaziflam + metribuzin). O delineamento experimental foi inteiramente casualizado, com quatro repetições, em esquema fatorial 2 x 4, sendo duas técnicas de aplicação (pré e pós-plantio) e quatro doses do herbicida. Aos 10, 25, 40, 55 e 70 dias após a aplicação (DAA) foram avaliados visualmente os sintomas de fitotoxicidade e foi caracterizado o colmo principal da cana quanto à altura, o diâmetro, o número de folhas e o número de perfilhos da planta de cana-de-açúcar. Aos 70 DAA, além das características supracitadas, foram avaliados o número de folhas totais, área foliar do colmo principal e dos secundários, massa seca da parte aérea e das raízes. O herbicida indaziflam foi seletivo na aplicação em pós-plantio na menor dose testada para a cultivar RB966928, assim como o indaziflam + metribuzin, que foi seletivo para aplicação em pós-plantio nas doses até 75+960 g i.a. ha-1 para RB966928, sendo que a aplicação em pré-plantio dos dois herbicidas causou a morte das mudas das duas cultivares de cana-de-açúcar.
Weed interference in sugarcane is a determinant factor to maximum crop productivity and quality, especially among these itchgrass (Rottboellia cochinchinensis), whose importance has been growing in recent years. In order to manage these weeds aiming to minimize the interference, the knowledge of their periods of interference in sugar cane crops allows better placing of residual action herbicides. This work's objective is to determine the interference period of itchgrass in sugar cane, the critical density of itchgrass that interferes on the development of pré-sprouted seedlings of sugar cane and their resprouting and the selectivity of the herbicides Indaziflam and Indaziflam + Metribuzin on pré-sprouted seedlings of sugar cane. To determine the periods of interference of itchgrass on sugar cane, the experiment was carried out in a commercial area with the CTC14 variety planted on january. The periods of cohabitation or control were 0-23, 0-37, 0-44, 0-58, 0-72, 0-92, 0-122, 0-240, 0-300, 0-450 days after planting. Given a 5% productivity reduction tolerance on the sugar cane crop with infestation of itchgrass predominantly, the period before interference found was 54 days, and the total prevention period was 130 days. There was a 26,4% reduction on productivity when the total lack of weeds and the presence of weeds during the complete cycle are compared; the total retrievable sugar value diminished with the increase of cohabitation period. To determine the densities of R. cochichinensis that interfere on the develoment of pré-sprouted seedlings and their effect on resprouting, the outline applied was randomized blocks with four replications, with Itchgrass population of 1; 2; 4; 8 and 16 plants per vase for 'RB855156' and 1; 2; 8 and 16 plants per vase for 'CTC14', and the trial white sugarcane plant in the absence of itchgrass. For the Itchgrass the treatments were composed by the various densities in presence and absence of sugarcane. At 25, 55, 85 and 120 days after planting of seedlings were analyzed, for the main stalk, the height, diameter, number of leaves and tillers. At 120 days after planting were also assessed the leaf count, leaf area and dry matter. The plants were cut at the base, keeping the lower parts of both varieties in absence of weeds for 90 days to analyze the resprouting. The growth of the itchgrass' population did not interfere on the assessed characteristics of the main stalk, but lowered the tiller count, the number of leaves and also lowered tiller leaf area and dry matter. For the 'RB855156' there was no resprouting 90 days after cut. The weed suffered intraspecific competition on the larger tested densities. The selectivity experiment was split on four parts, applying two varieties of sugar cane (RB966928 and CTC14), with the pré-sprouted seedlings method, and two herbicides (Indaziflam and Indaziflam + Metribuzin). The outline applied was completely randomized with four replications, in a 2 x 4 factorial scheme, with two applying techniques (pre and post planting) and four doses of herbicide. At 10, 25, 40, 55 and 70 days after application the fitotoxicity symptoms were visually analyzed, and the main stem was characterized for height, diameter, leaf count and tiller count. At 70 days were also analyzed the total leaf count, main and secondary stems' leaf area, dry mass of roots and aerial part. The herbicide Indaziflam was selective for the RB966928 variety when applied post planting with the lower dose, Indaziflam + Metribuzin was selective for the RB966928 variety when applied post planting with doses as high as 75+960 g i.a. ha-1. The application pre planting of both herbicides resulted on death for both varieties.
Weed interference in sugarcane is a determinant factor to maximum crop productivity and quality, especially among these itchgrass (Rottboellia cochinchinensis), whose importance has been growing in recent years. In order to manage these weeds aiming to minimize the interference, the knowledge of their periods of interference in sugar cane crops allows better placing of residual action herbicides. This work's objective is to determine the interference period of itchgrass in sugar cane, the critical density of itchgrass that interferes on the development of pré-sprouted seedlings of sugar cane and their resprouting and the selectivity of the herbicides Indaziflam and Indaziflam + Metribuzin on pré-sprouted seedlings of sugar cane. To determine the periods of interference of itchgrass on sugar cane, the experiment was carried out in a commercial area with the CTC14 variety planted on january. The periods of cohabitation or control were 0-23, 0-37, 0-44, 0-58, 0-72, 0-92, 0-122, 0-240, 0-300, 0-450 days after planting. Given a 5% productivity reduction tolerance on the sugar cane crop with infestation of itchgrass predominantly, the period before interference found was 54 days, and the total prevention period was 130 days. There was a 26,4% reduction on productivity when the total lack of weeds and the presence of weeds during the complete cycle are compared; the total retrievable sugar value diminished with the increase of cohabitation period. To determine the densities of R. cochichinensis that interfere on the develoment of pré-sprouted seedlings and their effect on resprouting, the outline applied was randomized blocks with four replications, with Itchgrass population of 1; 2; 4; 8 and 16 plants per vase for 'RB855156' and 1; 2; 8 and 16 plants per vase for 'CTC14', and the trial white sugarcane plant in the absence of itchgrass. For the Itchgrass the treatments were composed by the various densities in presence and absence of sugarcane. At 25, 55, 85 and 120 days after planting of seedlings were analyzed, for the main stalk, the height, diameter, number of leaves and tillers. At 120 days after planting were also assessed the leaf count, leaf area and dry matter. The plants were cut at the base, keeping the lower parts of both varieties in absence of weeds for 90 days to analyze the resprouting. The growth of the itchgrass' population did not interfere on the assessed characteristics of the main stalk, but lowered the tiller count, the number of leaves and also lowered tiller leaf area and dry matter. For the 'RB855156' there was no resprouting 90 days after cut. The weed suffered intraspecific competition on the larger tested densities. The selectivity experiment was split on four parts, applying two varieties of sugar cane (RB966928 and CTC14), with the pré-sprouted seedlings method, and two herbicides (Indaziflam and Indaziflam + Metribuzin). The outline applied was completely randomized with four replications, in a 2 x 4 factorial scheme, with two applying techniques (pre and post planting) and four doses of herbicide. At 10, 25, 40, 55 and 70 days after application the fitotoxicity symptoms were visually analyzed, and the main stem was characterized for height, diameter, leaf count and tiller count. At 70 days were also analyzed the total leaf count, main and secondary stems' leaf area, dry mass of roots and aerial part. The herbicide Indaziflam was selective for the RB966928 variety when applied post planting with the lower dose, Indaziflam + Metribuzin was selective for the RB966928 variety when applied post planting with doses as high as 75+960 g i.a. ha-1. The application pre planting of both herbicides resulted on death for both varieties.
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Palavras-chave
Competição, Densidade, Períodos, Rebrote, Rottboellia cochichinensis, Saccharum spp., Competition, Density, Addition series, Ratooning