flumioxazin50%WP 98%TC weed control herbicide weedicide agrochemical agricultural chemicals pesticide

                                                                                    flumioxazin

The use of herbicides, as an effective practice for controlling weeds in crops, has increased in the agricultural systems in Brazil mainly due to the introduction of herbicide-resistant plants in agriculture, such as soybean and maize . In Brazil, herbicides represent about 60% of the total pesticides used in agriculture. Although herbicides are important for agriculture, there is a concern about their fate in the environment and their impact on soil biological properties.

Biological properties are critically important to the ecosystem functioning since they are involved in soil organic matter decomposition, nutrient cycling, and degradation of pesticides, such as herbicides. Therefore, studies assessing the effect of herbicides on soil biological properties are important for evaluating soil quality and health. In addition, soil biological properties are more effective as indicators of soil quality than physical and chemical properties as they often show a faster response to an environmental impact.

As important and responsive biological properties, soil microbial biomass and enzyme activities are frequently recommended for evaluating the effects of herbicides on the soil environment. Soil microbial biomass represents the active part of soil organic matter and is involved in several functions in soil, presenting a rapid turnover of soil C, N, and P; while enzymes are a suitable indicator of the catabolic activity of soil microorganism. These biological properties are highly sensitive to detect soil disturbance after the application of chemicals, such as herbicides. For example, glyphosate, one of the most important herbicides used is soybean crops, presents a transitory and short-term effect on soil microbial biomass and activity.

Currently, glyphosate is being replaced by imazethapyr and flumioxazin in the weeds control in soybean crops, since these herbicides provide a high spectrum of action against weeds. Imazethapyr, an herbicide belonging to the imidazoline family, acts on the grass and broadleaf weeds, being recommended for use in soybean cultivation. It has a mode of action on cell metabolism and could influence the accumulation of microbial C. Flumioxazin, that belongs to the N-phenylphthalimide chemical family, is a soil-applied herbicide recommended for broadleaf weeds control in soybean, peanut, and vineyard. It has a mode of action on the protoporphyrinogen oxidase, presenting anti-microbial effect and could inhibit some enzymes.

The application of imazethapyr in the soil has shown a different effect on soil microbes. A previous study conducted by Perucci and Scarponihas shown that imazethapyr, when applied at the recommended field rate for soybean (1.6 mg kg−1), had no adverse effect on soil microbial biomass and activity. However, in a field study during two years, Zhang et al. have found that the application of imazethapyr (0.1, 1 or 10 mg kg−1 soil) changed the content of microbial biomass C. These studies have shown that would be an influence of the history of application on soil microbial biomass and, probably, enzymes activity. On the other hand, there are no studies about the effect of flumioxazin on soil microbial biomass and enzyme activity. So far, the available studies about flumioxazin focused on its dissipation and movement in the soil, rather than its effects on microbial biomass.

Although the use of a mixture of herbicides seems to be more effective in controlling weeds, it could present a complex and larger effect on non-target organisms than the individual compounds. Therefore, studies evaluating the effects of the separate application of the herbicides or in a mixture on soil microbial biomass and enzyme activity are necessary for a better understanding of their effects on soil biological properties. In this context, we hypothesized that (1) the history of herbicides application and their different mode of actions could influence the soil microbial biomass and enzyme activity; and (2) there would be a different effect of the mixture in comparison with the individual compounds. We, therefore, addressed the responses of soil microbial biomass and enzymes activity to the application of imazethapyr and flumioxazin and their mixture in a tropical soil.