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Efeito da interação do nicosulfuron e chlorpyrifos sobre o banco de sementes e os atributos microbianos do solo Effect of sequential nicosulfuron and chlorpyrifos application on seed bank and soil microbial characteristics

By Taciane Almeida de Oliveira, José Barbosa dos Santos, Gessimar Nunes Camelo, Rafael Grossi Botelho and Thiago Magalhães de Lázari

Abstract

Considerando o período de competição de plantas daninhas e a incidência da lagarta-do-cartucho na cultura do milho, há necessidade de aplicação, em curto intervalo de tempo, de herbicidas e de inseticidas, principalmente o nicosulfuron e o chlorpyrifos. O objetivo deste estudo foi avaliar o efeito da aplicação sequencial do nicosulfuron e do chlorpyrifos sobre a emergência de plântulas do banco de sementes, a taxa de desprendimento de CO2 (respiração basal) e o C da biomassa microbiana (CBM) do solo. Foi realizada aplicação sequencial, em solo, do nicosulfuron (doses de 0 a 64 g ha-1) associado ou não ao chlorpyrifos (0 e 240 g ha-1). Aos 20, 40 e 60 dias após a aplicação (DAA) dos produtos, todas as plântulas emergidas do banco de sementes foram identificadas em nível de espécie, sendo estimadas a frequência, densidade e abundância, além do índice de valor de importância (IVI). Aos 60 DAA, determinou-se também a taxa de desprendimento de CO2, o CBM e o quociente metabólico (qCO2), por meio da relação entre o CO2 acumulado e o CBM total do solo. A aplicação alterou severamente a massa de plântulas secas e o número de espécies nas doses superiores a 20 g ha-1 do nicosulfuron. Na presença do herbicida, as espécies com maior IVI foram Boehavia diffusa e Commelina benghalensis. Quanto aos bioindicadores do solo, foi observado decréscimo na taxa da respiração basal do solo com o aumento da dose aplicada do nicosulfuron associado ao chlorpyrifos, sem efeito na ausência do inseticida. Houve decréscimo linear no CBM em todos os casos, independentemente da aplicação do chlorpyrifos; entretanto, observou-se uma taxa de decréscimo 4,5 vezes maior para o solo que recebeu esse inseticida em conjunto com o nicosulfuron. A avaliação do qCO2 confirmou o efeito negativo da aplicação do inseticida e do herbicida. Conclui-se que a aplicação de chlorpyrifos + nicosulfuron promove impacto negativo sobre o banco de sementes e sobre a atividade microbiana do solo.<br>In the period of competition of weeds and the incidence of fall armyworm in the corn crop there is a need for herbicide and insecticide such as nicosulfuron and chlorpyrifos application within short time intervals. The aim of this study was to evaluate the effect of sequential applications of nicosulfuron and chlorpyrifos on the emergence of seedlings of the seed bank in the soil, the basal CO2 emission rate, and the microbial biomass carbon (MBC) of soil. Sequential applications of nicosulfuron (doses from 0 to 64 g ha-1) with or without chlorpyrifos (0 and 240 g ha-1) were performed. At 20, 40 and 60 days after application (DAA) of the products, the species of all seedlings that emerged from the seed bank were identified, and the frequency, density and abundance estimated, as well as the importance value IV. Sixty DAA the CO2 emission rate and CBM were were also determined, and based on the relationship between the accumulated CO2 and total soil MBC the metabolic coefficient (qCO2) was estimated. The application of nicosulfuron rates of over 20 g ha-1 severely affected the seedling dry weight and number of species. In the presence of the herbicide, the species with highest IV were Boehavia diffusa and Commelina bengalensis. There was a decrease in the basal soil respiration rate with increasing nicosulfuron doses, in the presence as well as in the absence of the insecticide chlorpyrifos. There was a linear decrease in MBC in all cases regardless of the chlorpyrifos application, although the reduction was 4.5 times greater in soil that received the combined application of the insecticide and nicosulfuron. The qCO2 confirmed the negative effect of the application of insecticide and herbicide. It was concluded that the application of chlorpyrifos + nicosulfuron causes a negative impact on the seeds in the soil and the soil microbial activity

Topics: agrotóxico, carbono da biomassa microbiana, impacto ambiental, sinergismo, pesticides, microbial biomass carbon, environmental impact, synergism, Plant culture, SB1-1110, Agriculture, S, DOAJ:Plant Sciences, DOAJ:Agriculture and Food Sciences, Agriculture (General), S1-972
Publisher: Sociedade Brasileira de Ciência do Solo
Year: 2009
DOI identifier: 10.1590/S0100-06832009000300009
OAI identifier: oai:doaj.org/article:44db16fc7f704cee8b028fefda1b62b6
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