Respiração microbiana do solo sob doses de glyphosate e de imazapyr

A degradacao microbiana dos herbicidas no solo e influenciada por diversos fatores, dentre esses as caracteristicas fisicas e quimicas do solo e da propria molecula, que agem continuamente determinando a sua magnitude. Em razao da grande variabilidade de respostas apresentadas por essas moleculas no solo e das poucas informacoes sobre o seu comportamento em ambientes tropicais, no que diz respeito a sua degradacao, e que foi realizada uma serie de experimentos, em laboratorio, objetivando verificar a resposta da atividade microbiana do solo, pelo metodo da evolucao do CO2 do solo, sob doses crescentes do glyphosate e do imazapyr (0; 4; 8 e 12 L ha-1 do produto comercial Roundup S.Aq.C. e Arsenal 250 S.Aq.C., respectivamente), em solos de diferentes texturas e composicao quimica, sob tres conteudos de umidade (40, 70 e 100% do equivalente de umidade). Os resultados obtidos permitiram concluir que: a) a microbiota do solo e capaz de utilizar o glyphosate e o imazapyr como fontes de carbono; b) a umidade do solo influencia a capacidade de os microrganismos degradarem o glyphosate e o imazapyr; c) a umidade de 40%, nos solos avaliados, proporcionou as menores respostas da atividade dos microrganismos, independentemente das doses dos herbicidas; e d) o efeito das doses do imazapyr sobre a atividade microbiana do solo e influenciado pelas caracteristicas fisicas e quimicas dos solos.

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