Effect of Volcanic Ash on Coffee Plants

We have written about how coffee tends to be grown in regions with rich volcanic soil such as the mountains of Colombia. We also recently noted that coffee grown in the South Pacific is grown on land fertilized by volcanic ash. Before and after photos of the recent eruption of an undersea volcano in the Tonga island group show some islands dusted gray with ash and some completely black with all green plant life invisible. What are the short as well as long term effects of volcanic ash on coffee plants?

Volcanic Ash Effects on Coffee Plants

Many times lava flow from volcanoes wipes out whole fields of coffee but only covers adjacent fields with ash. The eruption of Nevado del Ruiz in Colombia in 1985 sent hot mud down the mountain to largely cover the town of Armero killing 20,000 people. Years later the town was never rebuilt but coffee farms cover the region benefitting from the rich soil. But, what happens in the short term? Volcanic ash is usually acidic and sufficient amounts of ash can cover plants and block sunlight.

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Nevado Ruiz Volcano

Volcanic Ash and Acid Rain

All plant life is affected by the acidity of volcanic ash. If it rains while significant amounts of ash are in the air there is acid rain. The EPA reports that acid rain can directly affect all plant life.

Dead or dying trees are a common sight in areas affected by acid rain. Acid rain leaches aluminum from the soil.  That aluminum may be harmful to plants as well as animals. Acid rain also removes minerals and nutrients from the soil that trees need to grow. At high elevations, acidic fog and clouds might strip nutrients from trees’ foliage, leaving them with brown or dead leaves and needles. The trees are then less able to absorb sunlight, which makes them weak.

Coffee plants become dehydrated due to acid rain acidifying the soil excessively and this not only hurts the plants but reduces the quality of the coffee as well.

How Long Can Coffee Survive in the Dark?

If there is enough ash, like on some of the islands in the Tonga group, coffee plants are covered totally and deprived of light. Luckily, coffee is by nature a plant that grows under the forest canopy, a low-light plant. This sort of plant can live between 12 to 20 days when deprived of light. The good news for coffee on Tonga in this regard is that November to April is the rainy season with an average of 8 inches of rain a month and the initial large volcanic eruption occurred in January. So, rain could wash off much if not all of the ash that might otherwise kill coffee plants.

The other part of this issue is that coffee is typically planted on slopes. As such, rain is more likely to carry the ash downhill and off of coffee plants.

The short term effects of volcanic ash on coffee plants can be mildly damaging or devastating, depending on the amounts of ash and its acidity. Nevertheless, over the long term the ash fertilizes the soil and makes for a better coffee crop.

Effect of Volcanic Ash on Coffee Plants – Slideshare Version

Effect of Volcanic Ash on Coffee Plants – PDF

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