Potencial de lixiviação de herbicidas utilizados na cultura da cana-de-açúcar em um solo de textura média
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2017-10-06
Autores
Silva, Ana Paula da [UNESP]
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Universidade Estadual Paulista (Unesp)
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RESUMO - Geralmente os estudos de lixiviação em cana de açúcar são realizados utilizando-se métodos de bioensaios com condição edafoclimática específica, além de utilizarem amostras de solo deformadas. Estudar o processo de lixiviação em condições reais de campo, mantendo-se a integridade da estrutura do solo e sob condições edafoclimaticas naturais, vem a ser a forma mais confiável de analisar o comportamento dos herbicidas no solo. O objetivo deste trabalho foi avaliar o potencial de lixiviação dos herbicidas S-metolachlor, metribuzin, sulfentrazone e tebuthiuron em precipitações pluviométricas naturais, em um solo de textura média (Latossolo Vermelho Distrófico), em condições de campo através de plantas bioindicadoras. As amostras foram coletadas em colunas de PVC com 30 cm de altura e 15 cm de diâmetro, introduzidas no solo de forma que se preservou a estrutura natural do solo. As colunas foram retiradas cuidadosamente escavando ao seu redor, mantendo a integridade original do solo durante a coleta das amostras que ocorreu após a aplicação dos herbicidas nas doses recomendadas no solo e posterior acúmulo das precipitações estipulada ao ambiente (50, 91 e 131 mm de chuva). As colunas foram separadas com corte longitudinal para a semeadura das espécies bioindicadoras (Brachiaria plantaginea, Cucumis sativus, Lactuca sativa e Sorghum bicolor), de maneira que pudessem emergir um número uniforme de plantas em cada metade das colunas. O delineamento experimental utilizado foi inteiramente casualizados com quatro repetições, dispostos em um esquema fatorial 3 x 8. Os fatores referem-se aos três índices de precipitação acumulada (50, 91 e 131mm) e as 8 camadas de profundidade analisadas no perfil do solo (0-3, 3-6, 6-9, 9-12, 12-15, 15-20, 20-25, 25-30 cm). Após a semeadura, para as avaliações das plantas bioindicadoras nas colunas adotou-se a escala de notas de ‘0’ a ‘100’% de fitotoxicidade, aos 5, 7, 9 e 11 dias após a semeadura (DAS). As respostas das espécies bioindicadora ao residual de cada herbicida utilizado foi variável, mostrando-se dependente da precipitação pluvial e do tipo de herbicida utilizado. A lixiviação do S-metolachlor no solo estudado foi dependente da quantidade de precipitação recebida e a máxima profundidade visual detectada foi de 12- 15cm, sendo o pepino a espécie mais sensível a presença do herbicida no solo. A lixiviação do metribuzin também foi dependente da quantidade de precipitação recebida para as plantas bioindicadoras pepino, alface e capim-marmelada, sendo os sintomas visualizados até a camada 9-12cm do perfil do solo. A lixiviação do sulfentrazone mostrou-se dependente da quantidade de precipitação recebida, sendo os sintomas de intoxicação nas plantas de pepino e capim-marmelada visualizados até a camada de 9-12 cm no perfil do solo. A lixiviação do tebuthiuron foi dependente da quantidade de precipitação recebida; dentre as plantas bioindicadoras utilizadas, apenas o sorgo não seria indicada para visualização dos sintomas de intoxicação causados pelo herbicida no perfil do solo neste estudo.
Usually leaching of studies in sugarcane are performed using methods bioensaio at specific climate and soil condition , besides using deformed soil samples. Studying the leaching process under real field conditions, maintaining the integrity of the soil structure specific climate and soil condition, is the most reliable way to analyze the behavior of herbicides in the soil. The objective of this study is to evaluate the leaching potential of herbicides S-metolachlor, metribuzin, sulfentrazone and tebuthiuron on natural rainfall, in a medium textured soil (Latossolo Vermelho Distrófico) under conditions field using bioindicator plants. Samples were collected in PVC columns with 30 cm high and 15 cm in diameter, introduced in soil so that the natural structure of the soil was preserved. The columns were removed carefully mind digging around, keeping the original integrity of the soil during collection of samples that occurred after application of herbicide at recommended doses for soil and subsequent accumulation of precipitation stipulated to the environment (50, 91 e 131 mm of rain). The columns were separated by a longitudinal section for the sowing of bioindicator species (Brachiaria plantaginea, sativu Cucumis, Lactuca sativa and Sorghum bicolor), So that a uniform number of plants could emerge in each half of the columns. The experimental design was entirely randomized with four replications in a factorial 3 x 8. The factors relate to the three indices of rainfall (50, 91 e 131) and eight layers analyzed in depth profile of soil (0-3, 3-6, 6-9, 9-12, 12-15, 15-20, 20-25, 25-30 cm). After sowing, for the evaluation of bioindicator plants in the columns adopted the scale from 0 to 100% phytotoxicity, at 5, 7, 9 and 11 days after sowing (DAS). The response of bioindicator’s species for each residual herbicide used was variable, showing that this is dependent on rainfall and the type of herbicide used. Leaching of Smetolachlor at studied soil was dependent on the amount of rainfall received and the maximum visual depth detected was 12-15cm, being the cucumber the most sensitive species the presence of the herbicide in the soil. The leaching of metribuzin was also dependente on the amount of precipitation received for bioindicator plants, cucumber, lettuce and grass. Being that the symptoms of the herbicide were visualized until the layer 9-12 cm of soil profile. The vi leaching of sulfentrazone was dependente on the amount of precipitation received, being the symptoms of intoxication in the cucumber and grass plants observed until the 9-12cm of soil profile. Tebuthiuron leaching was dependente on the amount of precipitation received; Into the group of the bioindicator plants used, only sorghum would not be indicated for the visualization of the intoxication symptoms caused by the herbicide in the soil profile in this study. Keywords: sugar cane, herbicides, soil texture, mobility, water depths.
Usually leaching of studies in sugarcane are performed using methods bioensaio at specific climate and soil condition , besides using deformed soil samples. Studying the leaching process under real field conditions, maintaining the integrity of the soil structure specific climate and soil condition, is the most reliable way to analyze the behavior of herbicides in the soil. The objective of this study is to evaluate the leaching potential of herbicides S-metolachlor, metribuzin, sulfentrazone and tebuthiuron on natural rainfall, in a medium textured soil (Latossolo Vermelho Distrófico) under conditions field using bioindicator plants. Samples were collected in PVC columns with 30 cm high and 15 cm in diameter, introduced in soil so that the natural structure of the soil was preserved. The columns were removed carefully mind digging around, keeping the original integrity of the soil during collection of samples that occurred after application of herbicide at recommended doses for soil and subsequent accumulation of precipitation stipulated to the environment (50, 91 e 131 mm of rain). The columns were separated by a longitudinal section for the sowing of bioindicator species (Brachiaria plantaginea, sativu Cucumis, Lactuca sativa and Sorghum bicolor), So that a uniform number of plants could emerge in each half of the columns. The experimental design was entirely randomized with four replications in a factorial 3 x 8. The factors relate to the three indices of rainfall (50, 91 e 131) and eight layers analyzed in depth profile of soil (0-3, 3-6, 6-9, 9-12, 12-15, 15-20, 20-25, 25-30 cm). After sowing, for the evaluation of bioindicator plants in the columns adopted the scale from 0 to 100% phytotoxicity, at 5, 7, 9 and 11 days after sowing (DAS). The response of bioindicator’s species for each residual herbicide used was variable, showing that this is dependent on rainfall and the type of herbicide used. Leaching of Smetolachlor at studied soil was dependent on the amount of rainfall received and the maximum visual depth detected was 12-15cm, being the cucumber the most sensitive species the presence of the herbicide in the soil. The leaching of metribuzin was also dependente on the amount of precipitation received for bioindicator plants, cucumber, lettuce and grass. Being that the symptoms of the herbicide were visualized until the layer 9-12 cm of soil profile. The vi leaching of sulfentrazone was dependente on the amount of precipitation received, being the symptoms of intoxication in the cucumber and grass plants observed until the 9-12cm of soil profile. Tebuthiuron leaching was dependente on the amount of precipitation received; Into the group of the bioindicator plants used, only sorghum would not be indicated for the visualization of the intoxication symptoms caused by the herbicide in the soil profile in this study. Keywords: sugar cane, herbicides, soil texture, mobility, water depths.
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Palavras-chave
Cana-de-açúcar,, Herbicidas, Textura do solo, Mobilidade, Lâminas de água