Effects of foliar-applied choline-aspartate ionic liquid on maize (Zea mays L.) metabolism and rhizosphere soil characteristics under field conditions.

Choline-based ionic liquids have emerged as promising materials with diverse applications in electrochemistry, biomaterials, and environmental remediation technologies. However, their impacts on the agricultural ecological environment remain relatively underexplored. In this study, the regulatory effects of foliar-sprayed choline-aspartate ionic liquid ([Chl][Asp] IL) on maize growth and rhizosphere soil properties were analysed during a two-year field experiment. Compared with the control, [Chl][Asp] IL treatment increased maize grain yield by an average of 14.4 % and grain protein content by 8.85 % over the two years, while significantly enhancing the activities of key enzymes involved in leaf carbohydrate and nitrogen metabolism. Metabolomic profiling identified significantly increased choline glycerophosphate in leaves following [Chl][Asp] IL exposure. In the rhizosphere soil, organic matter content increased by an average of 17.9 %. Notably, of the 58 differential metabolites identified, 45 were upregulated in [Chl][Asp] IL-treated rhizospheres, with lipids constituting the predominant category (61.1 %). Collectively, the results confirm the dual regulatory effects of [Chl][Asp] IL on both maize physiology and rhizosphere functionality, providing a theoretical framework for its application in crop yield and soil quality improvement.