Abstract
Climate change has continuously increased drought risk. Alternative economic, sustainable, and practical solutions are still needed to address this risk. In this study, conducted in Izmir, Türkiye, we used organic amendments, biochar, and vermicompost in combination with local tomato landraces as a strategy against drought stress. Four landraces, 'Olympia,' 'Areti,' 'TR40430' and 'TR43513' were selected from the Mediterranean Basin according to their performance to drought within the scope of the VEGADAPT Prima Project. 'Moneymaker' was used as a control under three irrigation treatments. Full irrigation (Ir100) was carried out to replenish the soil moisture to field capacity. For deficit irrigation, 70% (Ir70) and 40% (Ir40) of the water applied in the Ir100 irrigation was provided, respectively. Utilization of stable carbon-rich organic amendments mitigated the adverse effects of limited irrigation on plant growth, yield, water use efficiency, and soil microbial activity. Plant height and fresh and dry weight of vegetative parts were decreased, while leaf thickness and chlorophyll index were increased in the deficit irrigation. The total yield decreased by over 45% in Ir40 compared to Ir100 and Ir70. The total soluble solids, titratable acidity, fruit dry weight, and fruit firmness increased with water deficit, while fruit juice pH decreased. Irrigating at Ir70 levels with vermicompost or biochar significantly enhanced microbial activity, maintaining or improving function under the stricter Ir40 regime, though with different effects. The additive main effects and multiplicative interaction (AMMI) model was used to evaluate the overall adaptability of the studied landraces. 'TR40430' gave the best total yield on average, however, it showed the lowest results in terms of water use efficiency (WUE). 'Areti' was as good as cv. 'Moneymaker' in WUE. AMMI analysis also indicated the improvement of the effects of microbial activity on landraces. These results highlight the crucial role of organic amendments in enhancing soil resilience to water scarcity and supporting sustainable agricultural practices amid climate challenges.