Foram estudados os efeitos do metalaxil sobre amicrobiota de solos coletados nos municípiospaulistas de Aguai, Estiva Gerbi e Jaguariúna (Brasil),suplementados com doses de 3 e 30 μg i.a. g-1 demetalaxil pelo período de 32 dias. Popula??es debactérias, actinomicetos e fungos foram monitoradasmediante contagem em placas com meios de culturaseletivos e pela atividade enzimática da fosfataseácida (Pase) e desidrogenase (Dhase). A Pase foiavaliada pelo método da p-nitrofenilfosfatase e aDhase pela quantifica??o do vermelho formazanproduzido. Houve predominancia de popula??esbacterianas em todos os solos, sendo os maioresvalores de UFC g-1 observados nos solossuplementados com a dose de 30 μg i.a. g-1 demetalaxil. Popula??es de fungos apresentaramacentuado decréscimo após a incorpora??o docomposto. A atividade Dhase foi inibida pela presen?ade metalaxil nos solos arenoso e controle. No soloargiloso houve acréscimo dessa atividade, maissignificativo no período de 7 a 21 dias, nas duasdoses de suplementa??o avaliadas. A atividade daPase foi inibida em todos os três solos. METALAXIL ON SOIL MICROBIOT AND ENZYMATIC ACTIVITY Abstract The effects of Metalaxyl on soil microorganisms collected in Sao Paulo districts of Aguai, Estiva, Gerbi and Jaguariuna(Brazil), supplemented with doses of 3 and 30 μg a.i g-1 for the period of 32 days were studied. Bacterial, actinomycetsand fungi were monitored by plate counting and by acid phosphatase (Pase) and dehydrogenase enzymatic activity(Dhase). The Pase was evaluated by the method of p-nitrophenilphosphatase and the Dhase by the quantification of theproduced red formazan. Predominance of bacterial population was observed in all soils, being the higher values ofCFU g-1 observed in soils supplemented with the dose of 30 μg a.i g-1 of Metalaxyl. Fungal population presented accentuateddecrease after compost incorporation. Dhase activity was inhibited by the presence of Metalaxyl in sandy and controlsoils. In clay soils the activity was incremented, being more significant in the period of 7 to 21 days, in both supplementationdoses. Pase activity was inhibited in all three soils.
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