Influence of soil attributes and sorption coefficient in defining diuron doses

The selectivity of diuron for most crops, is due to the positioning of its molecule in the soil profile. Therefore, it is necessary to know the interactions of diuron's molecule with soil matrix to define recommended doses from an agronomic and environmental standpoint. This research aimed to estimate the influence of soil attributes and sorption coefficient (Kf) on the definition of diuron doses. Experiments were conducted to quantify the Kf of diuron in different soils and determine the doses in each soil that caused 80% intoxication (C80 intoxication) and 80% decreased accumulation of aerial parts plants (C80 DMAP) of Eleusine indica. After that, a correlation analysis was performed between the soil physical-chemical attributes, diuron Kf, and C80 of E. indica intoxication. Diuron Kf ranged from 1.8, in the ultisol with 0% of manure content, to 8.8, in the oxisol with 40% of manure content. Eleusine indica C80 ranged from 66.3, in the oxisol with 0% of manure content, to 568.3 g a.i. ha-1, in the ultisol with 40% of manure content, while C80 of aerial part dry matter reduction ranged from 57.5 to 521.6 g a.i. ha-1 in the same soils. C80 intoxication positively correlated with organic matter content and Kf. It was concluded that organic matter content was determinant in diuron sorption and intoxication for E. indica. Changes are necessary in the dosing recommendation criteria in the label of diuron, with its recommendation being primarily based on the organic matter content.