Allelopathic compounds, released by plants and other organisms, have garnered increasing interest in agriculture due to their ability to influence crop development both positively and negatively [1]. At the same time, agriculture faces the challenge of developing sustainable production systems that ensure high-quality food without compromising natural resources. In this context, the use of amendments emerges as a key strategy to enhance soil fertility, promote crop growth, and optimize resource utilization, thereby fostering more sustainable agriculture [2]. This study analyzes how the addition of two amendments, biochar (BC) and olive-mill waste (OMW), affects the bioavailability and bioactivity of the phytohormone S-abscisic acid (S-ABA) in a soil. The nature of the amendment influenced S-ABA activity by affecting its bioavailability in solution. S-ABA exhibited greater persistence in soil amended with OMW compared to soil amended with BC and unamended soil. The compound had a solution half-life (DT50) of 4.8 days (R2 = 0.983) in soil amended with OMW, whereas in BC-amended soil, its half-life was only 0.43 days (R2 = 0.977). The low availability of S-ABA in BC-amended soil was attributed to its sorption by the amendment. Consequently, the activity of S-ABA was also influenced by the presence of the amendments. In BC-amended soil, plant development was promoted, as the lower availability of the compound prevented it from exerting its inhibitory function. In contrast, in OMW-amended soil, the prolonged persistence of S-ABA allowed its inhibitory effect to last longer, leading to a reduction in plant growth. The results show that the application of soil amendments can be a key strategy for regulating the bioactivity of allelopathic compounds and enhancing crop performance in sustainable agricultural systems. References [1] Muñoz-Muñoz M.V., López-Cabeza R., Gámiz B., Celis R. 2024. Soil effects on the plant growth inhibitory activity of S‑abscisic acid. Biol. Fertil. Soils 60, 955-968. [2] Garbowski T., Bar-Michalczyk D., Charazińska S., Grabowska-Polanowska B., Kowalczyk A., Lochyński P. 2023. An overview of natural soil amendments in agriculture. Soil Tillage Res. 225, 105462.

Acknowledgment: Project PID2023-146470OB-I00 and pre-doctoral contract PRE2021-100664 financed by the Spanish Ministry of Science, Innovation, and Universities with EU ERDF and ESF+ funds.

Póster y resúmen del póster presentado en II ANDALUCÍA AGRO-HUB PhD students Meeting 11-12 marzo 2025 Estación Experimental del Zaidín, Granada

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