Fate of Abscisic Acid in Soil: Effect of the Addition of Organoclays and Biochar to an Agricultural Soil.

The use of biopesticides in agriculture is encouraged as a less harmful alternative to synthetic pesticides. It is known that certain amendments can dictate the final behavior and enantioselectivity of chiral agrochemicals in soils. In this sense, more information is needed regarding biopesticides. The aim of this work was to evaluate the effect of amending an agricultural soil with two organoclays, SA-HDTMA and Cloisite10A (Cloi10), and a biochar from apple wood (BC) on the sorption, dissipation and leaching of the biopesticide abscisic acid (ABA). Firstly, sorption-desorption isotherms of racemic ABA on the three sorbents were obtained. Sorption isotherms confirmed non-enantioselective sorption process and showed that SA-HDTMA displayed higher sorption towards ABA followed by Cloi10 and BC. The study was completed with incubation and leaching experiments with unamended soil and with soil amended with SA-HDTMA, Cloi10 and BC at a rate of 2% (w:w). Dissipation was always enantioselective, with S-ABA being degraded faster than R-ABA, and followed the same order for both enantiomers: unamended > Cloi10-amended >BC-amended >SA-HDTMA-amended soil. The leaching of both R- and S-ABA was delayed after amending soil, according to the sorption capacity of the sorbents. Only ABA leaching was almost suppressed only by addition of BC, likely due to a greater contribution of irreversible sorption. Our findings show that organoclays and BC affected differently the final behavior and enantioselectivity of ABA after its addition to soil. These amendments could impact the overall effectiveness of ABA, through different pathways, aspects to account for when used for agriculture purposes.

Acknowledgments: AGL2014-51897-R of MINECO and FACCE-JPI (Designchar4food).