Volcanic Ash Supercharges Plant Growth and Rebuilds Soil Life

A collaboration between scientists at UC San Diego’s Scripps Institution of Oceanography and the University of Greifswald in Germany has uncovered a powerful new way volcanoes give life to the Earth: volcanic ash can triple plant productivity and reshape entire soil ecosystems.

In a greenhouse experiment published in the journal Ecosphere, researchers led by Scripps Oceanography geologist Hubert Staudigel found that adding just a small percentage of basaltic volcanic ash to forest soil triggered explosive plant growth in Coleus (Plectranthus scutellarioides) and a dramatic restructuring of the soil microbiome.

“At around three percent ash, it’s as if the whole soil ecosystem flips a switch,” said Staudigel. “The plants grow taller with more aboveground biomass, reproduce more, and the microbial community in the soil reorganizes itself into a new, apparently more fertile system.”

The study revealed that while the ash itself contains nutrients like iron and magnesium, it wasn’t simply acting as a mineral fertilizer. Instead, the ash stimulated beneficial bacteria and fungi — many known as plant-growth-promoting rhizobacteria — while suppressing harmful parasitic worms known as nematodes. This biological reorganization helped plants draw more nitrogen and other nutrients from the soil, likely including some bioavailable iron from the ash boosting overall productivity threefold.

The team’s findings show that volcanic ash fertilization is a complex, indirect process that enriches life by reshaping the biology of soils — potentially offering a new natural strategy for sustainable agriculture and carbon sequestration.

“At first sight, volcanoes could easily have been viewed as destroyers of all life they touch,” said co-author and experimental plant biologist Juergen Kreyling of the University of Greifswald. “But our results show that they’re also powerful engineers of ecosystems — capable of renewing life and perhaps even drawing carbon out of the atmosphere.”

Because volcanic soils cover vast regions of Earth, near volcanic arcs such as those in Indonesia or the Andes or around oceanic volcanoes such as Iceland and Hawaii, the findings could have far-reaching implications for both post-eruption ecosystem recovery and possibly even climate mitigation. Volcanic ash could even become a valuable tool for low-cost, regenerative agriculture — using nature’s own materials to rejuvenate degraded lands or impoverished soils.

Besides Staudigel and Kreyling, researchers Mathilde Borg Dahl, Yohannes Tefsay, Ilka Beil and Tim Urich of the University of Greifswald in Germany co-authored the study, with support from the German Science Foundation (DFG), DAAD, and Scripps Institution of Oceanography.

Soil health is drawing increasing scientific interest as a means to improve agricultural productivity and as a climate solution to mitigate carbon emissions and support food security.  A new center at UC San Diego — the Soil Health Center — aims to serve as an epicenter for soil health research, education, and outreach by leveraging biological, chemical, physical, and social expertise on soil quality and connected ecological and human health.