Impact of herbicides on the microbial activity of soil cultivated with sugarcane / Impacto de herbicidas na atividade microbiana em solo cultivado com cana-de-açúcar

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

This work aimed at evaluating the impact of herbicides on the microbiological activity of soil cultivated with sugarcane. A first trial was installed in the laboratory with two bacterial isolates from the rhizosphere soil of sugarcane, Sac 4 and Sac 13, presenting, respectively, high and low potential for phosphate (P) solubilization. The growth and capacity of phosphate solubilization was evaluated under the presence of the herbicides trifloxysulfuron-sodium (Envoke), ametryn (Metrimex 500 SC), and trifloxysulfuron-sodium + ametryn (Krismat). The bacterial isolates showed distinct behaviors in relation to the presence of herbicides in the culture medium. For Sac 4, a reduction in growth was observed in the presence of trifloxysulfuron + ametryn. However, the herbicides did not affect Sac 13 growth. Phosphate solubilization activity for both isolates was not modified in the presence of the herbicides. In a second trial, soil samples from a sugarcane plantation were treated with ametryn, trifloxysulfuronsodium, and the commercial mixture at doses of 0, 1, 2, 4, and 8 times the dose of 10, 0.111, and 7.315 + 0.185 mg dm3 of the active ingredient, respectively. After herbicide application, the soil samples were incubated for 15 days and CO2 evolution (C-CO2) was evaluated every three days. After the incubation period, microbial biomass carbon (MBC), the metabolic quotient (qCO2), the phosphate solubilization potential, and the relative phosphate solubilization were evaluated. C-CO2 evolution was higher in the treatment with the highest dose of trifloxysulfuron-sodium and lower in the treatments with ametryn and trifloxysulfuron + ametryn compared to the control treatment. MBC and the qCO2 were negatively affected by ametryn and trifloxysulfuron-sodium + ametryn. Trifloxysulfuron-sodium did not affect significantly MBC and led to decreases in qCO2 that were dose-dependent. A third trial was installed under field conditions with treatments composed by two sugarcane varieties, RB867515 and SP80-1816, and the herbicides ametryn, trifloxysulfuron-sodium, trifloxysulfuron-sodium + ametryn, and sulfentrazone (Boral 500 SC). A control treatment with no herbicide application was also included. Herbicide application was done in post-emergence of the sugarcane. The rhizosphere soil was collected at 7, 14, and 28 days after herbicide application (DHA), and MBC, phosphate solubilization potential, relative phosphate solubilization potential, and the activity of phosphomonoesterase were determined. The application of metryn or trifloxysulfuron-sodium + ametryn led to decreases in MBC. The phosphate solubilization potential and relative phosphate solubilization differed for each sugarcane variety tested, with higher values for SP80-1816. These variables were reduced in the presence of ametryn and trifloxysulfuron- sodium + ametryn and stimulated trifloxysulfuron-sodium. Sulfentrazone did not affect phosphate solubilization. Phosphomonoesterase activity was influenced by the herbicides tested and showed higher activity in the rizhosphere of SP80-1816. The herbicide ametryn, applied singly or in combination with trifloxysulfuron-sodium, caused significant effects on the soil microorganisms. Trifloxysulfuron- sodium was shown to be less toxic and, in some cases, promoted beneficial effect for the soil microbiota.

ASSUNTO(S)

microbiota do solo saccharum spp. krismat ametryn fitotecnia trifloxysulfuron-sodium trifloxysulfuron-sodium saccharum spp. soil microbiota ametryn krismat

ACESSO AO ARTIGO

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