Tebuthiuron and hexazinone dynamics in soils under biochar application

Abstract

Soil application of biochar results in agricultural and environmental advantages, improving soils physical-chemical attributes and mitigating greenhouse gases effects. However, biochar can directly interact with pesticides either neutralizing its efficacy or requiring higher application rates, which enhance environmental contamination risks. The interactions between biochar and pesticides depend on soil and molecule properties, in addition to intrinsic biochar attributes that are affected by raw material (biomass) nature and pyrolysis temperature. Generally, there is an increase in sorption and persistence of xenobiotics when applying biochars yielded at high temperatures and with lignified residues. Tebuthiuron and hexazinone are pre-emergent herbicides, economically important to sugarcane production that may be negatively affected by biochar application, but the magnitude of these effects is unknown until the present moment. Therefore, this project aims to evaluate biochar effects on tebuthiuron and hexazinone environmental fate in contrasting soils. It will be assessed by studying: I) soil sorption of hexazinone and tebuthiuron in response to biochars application produced with different biomass types and pyrolysis temperatures; II) effects of biochar rates on Brachiaria control efficacy by these herbicides; and III) dissipation rates of these herbicides after biochar application. It is expected that this work will assist in decision making on the part of technicians, farmers, and legislators regarding the rational and sustainable use of biochar as a soil conditioner in Brazil. (AU)