Ashfall can have serious detrimental effects on agricultural crops and livestock depending mainly on ash thickness, the type and growing condition of a crop, the presence of soluble fluoride on the ash, timing and intensity of subsequent rainfall, condition of pasture and animals prior to ashfall, and availability of uncontaminated feed and water. Fluorine poisoning and death can occur in livestock that graze on ash-covered grass if fluoride is present in high concentrations; it may be advisable to sample and analyze ash or ash-coated vegetation to determine whether this potential hazard exists for livestock in areas covered with ash, even as thin as 1 mm. Livestock eating pasture that is contaminated with ash can suffer and die from gastrointestinal blockages. Shortages of uncontaminated feed and water after an ashfall can also lead to starvation.
Survival of agricultural crops and pasture is often severely limited when ash thickness is greater than 100-150 mm (4-6 in). Predicting the potential crop losses from ashfall, however, is difficult and usually exaggerated because of the great variety of environmental and plant conditions that exist in tropical and temperate areas during and after ashfalls of varying thicknesses.
The abrasiveness of ash can damage farm machinery and equipment, but increased maintenance and a few precautionary actions can significantly reduce the cost of keeping the machinery in working condition.
Ashfall can adversely affect crops and livestock in a variety of ways, but it is very difficult to predict exact consequences and associated costs of potential ash damage or mitigation measures. This is especially true for large explosive eruptions that result in ashfall over large areas and for a series of small eruptions that occur repeatedly over months to years. The information in this section identifies a range of known effects of ashfall on agricultural crops and livestock that can serve as a rough guideline for what can be expected. The information below is incomplete, however, and is not applicable to all situations because of the wide range of ash thickness and type and status of crops that can exist in different parts of the world at the time of an explosive eruption. Furthermore, there is a lack of detailed accounts of the effects of ashfall on individual farms in different regions, including the ways that farmers and governments have attempted to reduce the damaging consequences to their crops and livestock.
Additional information and case studies are needed to improve the usefulness of this section. If you have information and knowledge of case studies that can help the Ash Web Team prepare new material on the effects of ash on agriculture and livestock, please contact the Ash Web Team . Through your support and contributions, this Web site can be significantly improved to help farmers and others deal with future volcanic ashfalls.