Increasing freshwater scarcity alongside growing irrigation demand poses a major challenge for agricultural production. One potential response is the use of drought adaptation amendments: materials of natural or synthetic origin that, when applied to soil or crops, either increase water availability or improve plant performance under water stress. Because these amendments range from minerals and microorganisms to polymers and plant-derived compounds, they are often studied in separate disciplinary literatures rather than as a single category of inputs. Here, we review drought adaptation amendments for agricultural use and evaluate them along three dimensions: effectiveness in mitigating drought stress, economic feasibility, and environmental and human-health implications. Across amendment classes, effectiveness is achieved through several recurring pathways, including reduced soil evaporation, altered canopy energy balance, improved infiltration and soil water retention, improved rhizosphere and root access to retained water, and enhanced physiological tolerance to water deficit. No single amendment consistently performs best across all three criteria. Materials that strongly modify soil water dynamics can be effective but may be costly or environmentally risky, while lower-risk options often have smaller or more context-dependent effects. Among the most promising lower-risk options identified in this review are microbial inoculants, certain mineral amendments, and water-based plant extracts, though their effectiveness remains context-dependent. Future research should prioritize amendments that combine drought-mitigating effects with economic feasibility and minimal environmental or health risks.
Silber-Coats et al. (Thu,) studied this question.