Abstract
ABSTRACT Pre-emergence herbicides, such as indaziflam, have agronomic efficiency when available in the soil solution, mainly in the superficial layer (0-10 cm), the region with the highest concentration of weed seed bank. However, information about the sorption of indaziflam in Brazilian soils still is scarce, since most studies available in the literature were conducted in soils of temperate regions. The objective of this study was to estimate the sorption of indaziflam using high-performance liquid chromatography (HPLC) and bioassay in a Latossolo Vermelho-Amarelo (Oxisol) and in a Cambissolo (Inceptisol), at pH values of 5.1 and 6.1. In the biossay, Sorghum bicolor was used as an indicator plant. Quantitative indaziflam data were obtained by HPLC, and the sorption and desorption coefficients were determined in the soils using Freundlich isotherms. Increasing the pH of the two soils from 5.1 to 6.1 resulted in reductions of C50 and sorption coefficient values. Desorption, a parameter estimated only by HPLC, showed an inverse behavior to that of sorption, that is, the lowest desorption was observed in the condition of highest sorption. It is concluded that the increase in pH of the studied soils reduces indaziflam sorption, influencing the recommendations of this herbicide, from both the agronomic and the environmental points of view. When the goal is to verify the presence or absence of indaziflam in the studied soils, the bioassay technique has satisfactory efficiency. Chromatographic assay is necessary when quantifying the concentration of this herbicide in the soil.
Highlights
The interference of weeds in agricultural crops has been one of the main critical points of the production process
When herbicides are applied in preemergence, it is essential that they remain for a certain period of time available in the soil solution, that is, their bioavailability, and the process that controls this bioavailability is called sorption (SILVA; VIVIAN; OLIVEIRA JR., 2013; KHAN; BROWN, 2017)
The dose-response curves for percentage of intoxication and total dry matter accumulation of S. bicolor cultivated in the inert substrate, at 21 days after the application of indaziflam doses, are presented in Figures 1A and 1B, respectively
Summary
The interference of weeds in agricultural crops has been one of the main critical points of the production process. Chemical control with herbicides has been the most used strategy in weed control due to lower dependence on labor and higher efficiency in the control with selectivity to crops (FAOSTAT, 2018; SILVA et al, 2013a). When herbicides are applied in preemergence, it is essential that they remain for a certain period of time available in the soil solution, that is, their bioavailability, and the process that controls this bioavailability is called sorption (SILVA; VIVIAN; OLIVEIRA JR., 2013; KHAN; BROWN, 2017). Belonging to the alkylazine chemical class, it has as mechanism of action the inhibition of cell wall biosynthesis (JEFFRIES; GANON, 2016; BRABHAM et al, 2014; GUERRA et al, 2013). Inhibition probably occurs at some point in the crosslinking stage of cellulose microfibrils (JEFFRIES; GANON, 2016; KAAPRO; HALL, 2012).
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