Exposure of vegetables to simulated volcanic ashfall reveals production loss controlled by plant traits and growth stage

Explosive volcanic eruptions represent a serious threat to agriculture in many countries. Ashfall can cause substantial damage to crops, jeopardizing farmers' livelihoods and potentially endangering food security. Previous field-based studies have associated ash impact on crops with the deposit thickness, or, correspondingly, with the mass load. However, non-volcanic factors, including plant traits and growth stage, also influence the vulnerability of crops to ashfall. To accurately estimate the risk of crop production loss in ash-prone areas, it is essential to evaluate how these factors govern the impact of ash on crops. We grew leafy (lettuce, Lactuca sativa; hative d'Heverlée, and cabbage, Brassica oleracea; cabus de Chateaurenard) and bulb and root (onion, Allium cepa; blanc premier, and carrot, Daucus carota; hative d‘Oxhella) vegetables in a greenhouse and exposed them at two growth stages to simulated ash deposits ranging from 5 to 40 kg m⁻². Our results confirm that crop production loss increases with higher ash mass load, reaching 27%–69% for deposits of 20–40 kg m⁻². Additionally, they indicate a higher vulnerability of carrot and onion plants than previously reported. Lettuce and cabbage plants were more severely impacted by ash compared to onion and carrot plants, illustrating the role of plant traits in controlling ash interception and retention on foliage. Furthermore, the plant growth stage emerged as another vulnerability factor. Using the new impact data, we calculated a theoretical production loss in a cultivated area potentially affected by ashfall. This revealed that a significant portion of the crop production loss can be associated with low ash mass loads (5 kg m⁻²), emphasizing the importance of including distal regions in the impact assessment of ashfall on crops.