Dynamic effect of fresh and aged biochar on the behavior of the herbicide mesotrione in soils

Authors: GAMIZ, BEATRIZ - Instituto De Recursos Naturales Y Agrobiologia De Sevilla (IRNAS-CSIC); VELARDE, PILAR - Instituto De Recursos Naturales Y Agrobiologia De Sevilla (IRNAS-CSIC); Spokas, Kurt; COX, LUCIA - Instituto De Recursos Naturales Y Agrobiologia De Sevilla (IRNAS-CSIC)

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2019
Publication Date: 8/5/2019
Citation: Gamiz, B., Velarde, P., Spokas, K.A., Cox, L. 2019. Dynamic effect of fresh and aged biochar on the behavior of the herbicide mesotrione in soils. Journal of Agricultural and Food Chemistry. 67(34):9450-9459. https://doi.org/10.1021/acs.jafc.9b02618.
DOI: https://doi.org/10.1021/acs.jafc.9b02618

Interpretive Summary: We need to understand how biochar changes after it has been placed into various soils. This study investigated changes in the sorption behavior of a herbicide to fresh and aged biochars. The same biochar was aged for 6 months buried in mesh bags at 3 locations across the US (ID, WI, and SC). The biochar that was aged in the Wisconsin soil resulted in the largest increase in sorption behavior. Whereas the biochar that were aged in SC and ID were not significantly altered in their sorption behavior. The exact reason for these differences could not be conclusively demonstrated, but it is believed linked to the alterations in the dissolved organic compounds sorbed to the biochar and alterations to the metal salt content following soil incorporation. These results highlight the need to understand the mechanisms of chemical alterations to biochar resulting from soil exposure to properly assess longer term impacts of biochar additions. These results are significant to farmers and policy makers and will assist scientists and engineers in understanding the potential pathways for improved mechanisms of biochar’s chemical sorption behavior.

Technical Abstract: Biochar (BC) sorption capacity changes with its residence time in soil altering the bioavailability of pesticides in soil. In this study, we assessed the sorption, degradation, and leaching of the herbicide mesotrione in soil amended with fresh and field-aged biochars, when added to the soil at a rate of 2% (w/w). The aging process was performed by burying the fresh biochar at 10 cm depth in three soils located in different points across the USA [Wisconsin (ABC_WI), Idaho (ABC_ID) and South Carolina (ABC_SC)] for six months. ABC_ID and ABC_SC slightly increased the sorption of mesotrione in soils, whereas ABC_WI removed greater amounts of herbicide from the solution when compared to soil amended with fresh biochar. This was attributed to differences in water-soluble components and metal composition of the biochar. Consequently, the persistence of the herbicide in the amended soils with fresh biochar and ABC_ID and ABC_SC were similar to that in unamended soils, while ABC_WI slightly increased mesotrione half-life. Differences between treatments were detected in leaching studies although no direct relationship with the dissipation batch studies was found. Mesotrione leaching couldnot be detected in soil columns amended with ABC_WI and high for the rest of treatments (unamended>ABC_ID> fresh BC> ABC_SC). The outcomes from this work demonstrate that temporal variability of biochar sorption capacities due to soil exposure can occur altering the behavior in the soil of the herbicide mesotrione. These effects should be considered in order to optimize the performance of this herbicide in the rhizosphere after the addition of biochar to soils.