Abstract
ABSTRACT: Studies on herbicide behavior in soils may be performed using biological and chemical methods. The efficiency of the biological method depends on the indicator species sensitivity to low herbicide concentrations in the soil solution. Among the herbicides commonly used in Brazil for corn cultivation, tembotrione stands out. In the last agricultural seasons, the intoxication of some crops when cultivated in succession to corn has been reported, which may be attributed to tembotrione recommendations without the knowledge of their interactions with colloids of tropical soils. In this research, we selected an indicator plant species of tembotrione residues in the soil after sorting 12 species. The sorption of this herbicide was estimated in two Oxisols (Latossolo Amarelo and Latossolo Vermelho-Amarelo, Brazilian Soil Classification) and in a Histosol (Organossolo, Brazilian Soil Classification) with different attributes. Initially, after sorting the 12 plant species, the two most efficient in detecting tembotrione in the soil were selected. In the second stage, the most sensitive species was selected. In the third stage, tembotrione sorption was assessed in the three soils by using the selected species. Among the 12 species, Beta vulgaris and Brassica oleracea var. capitata were the most efficient in detecting tembotrione at low concentrations in the soil, being B. vulgaris (beet) the most sensitive. Thus, due to its ease of cultivation, high sensitivity, and fast initial growth, beet can be used as an indicator species of tembotrione presence in the soil solution. The sorption of this herbicide was higher in the Histosol and it is directly related to the organic matter content.
Highlights
The chemical method of weed control is the most used for all crops in Brazil, both by large and small farmers
Tembotrione has a systemic action on plants and acts to inhibit the biosynthesis of 4-hydroxyphenylpyruvate dioxygenase (HPPD), an important enzyme in the carotenoid synthesis route, which is essential in protecting the plant against high light intensity
In sensitive plants treated with this herbicide, a reduction of carotenoid concentration is observed in the leaves
Summary
The chemical method of weed control is the most used for all crops in Brazil, both by large and small farmers. Tembotrione belongs to the chemical group of tricetones and it has been widely used in Brazil to control weeds in corn. It presents a solubility of 28 g L-1, pKa of 3.2, and Koc of 66 mL g-1 (USEPA, 2007). In sensitive plants treated with this herbicide, a reduction of carotenoid concentration is observed in the leaves Under this condition, chlorophyll and photosynthetic membranes are degraded by photo-oxidation, which results in the appearance of intoxication symptoms characterized by an intense whitish coloring of leaves, evolving to necrosis and plant death (USEPA, 2007)
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