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Andisols: The Power of Volcanic Soil


Around the world, volcanic soil is often considered fertile soil suitable for growing crops, including coffee. Let’s learn about this land!

It is estimated that more than 800 million people – almost 10% of the world’s population – live within 100km of 1,431 active volcanoes around the world. Although volcanoes are incredibly destructive, active volcanoes still attract millions of tourists each year and provide a source of geothermal energy that can be harnessed to support local communities. Furthermore, volcanic material produced during the eruption can mix with the surrounding soil to create some of the world’s most fertile cropland.

The coffee plant, in particular, thrives in andisols, which are characterized by a set of physical, chemical and mineral properties that make it agronomically superior to other grounds. However, the land is only part of the story; The volcanic environment also provides other conditions for growing some of the best coffee in the world.

Andisols: The Power of Volcanic Soil


Much of the volcanic soil is formed by “tephra”. Tephra is a mixture of volcanic particles (ash) and rock fragments that are ejected from the volcano during each eruption and then fall to the ground. Over time, tephra breaks down and creates what we call Andisols.

Most volcanic soils are called Andisols or Andosols, which come from the Japanese words anshokudo and ando, meaning “dark soil”. Andisols are light and smooth and contain a high percentage of silicate glass, accumulating organic matter.

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Andisols – sức mạnh của đất núi lửa

Andisols are great for stimulating plant root growth for several reasons. First, they have a low density and a stable but porous structure. This allows the soil to retain water effectively and is relatively drought resistant. Because they are highly permeable, plant roots can also grow deep, draining water efficiently, preventing the roots from getting wet and rotting.

Coffee plants need many different nutrients to grow – mainly from the soil. In part, Andisols are fertile because they are relatively “young”; they retain many of the nutrients found in the bedrock. Although there are variations between volcanoes, Andisols generally contain phosphorus, potassium, calcium, magnesium, zinc, iron and boron, all of which are important for the growth of the coffee plant.

For example, potassium concentration affects the formation of coffee beans and the amount of sugar and citric acid content, which change the taste of coffee. Calcium is vital for root and leaf development, affecting the rate of fruit ripening, while boron improves crop yields. Studies have also shown that coffee plants are grown on soils rich in phosphorus and potassium often produce beans with better aroma, flavor, and acidity.


Andisols and volcanic eruptions


The fertility of volcanic soils and the growth of coffee grown there depend on the chemistry, nature and frequency of volcanic eruptions.

Eruptions can be divided into two categories: solid eruptions and explosive eruptions. Vigorous eruptions are mainly characterized by the explosion of lava, producing Andisols rich in iron and magnesium. On the other hand, explosive eruptions are marked by the outbreak of silica-rich volcanic ash and debris (or tephra). This material then blankets the soil around the volcano and creates Andisols rich in aluminium, sodium, and potassium.

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Much of the Andisols found around the world formed after eruptions. Andisols are less likely to form after powerful eruptions, as surfaces formed by lava flows can take thousands of years to decompose into the soil.

Many coffee-producing Latin American countries – including Colombia, Ecuador and Guatemala – lie around what is known as the “Pacific Ring of Fire”, which contains more than 75% of the world’s active and dormant volcanoes. . These countries have many powerful volcanic eruptions that produce abundant Andisols.

Because most of these volcanoes erupt after tens to hundreds of years, fresh tephras do not continuously fall to the surrounding ground. This protects the Andisols below from physical erosion and weathering, helping to preserve them over time.

It also means that fresh tephra is regularly replenished, providing a constant supply of nutrients to “replenish” the soil and maintain fertility.


Coffee from volcanic land


In addition to the nutrient-rich soils that volcanoes produce, the topography of many volcanic regions offers other benefits for coffee growing. The arabica plant thrives at altitudes between 1,000 and 2,000 meters above sea level and temperatures between 18 and 21°C.

Volcanoes are commonly found along high-altitude mountain belts, such as volcanic arcs in Central and South America. Coffee quality typically increases at higher altitudes, where temperatures are cooler, kernel development is slower, and fresh fruit ripens more slowly.

Volcanoes are commonly found along high-altitude mountain belts, such as volcanic arcs in Central and South America. Coffee quality typically increases at higher altitudes, where temperatures are more relaxed, kernel development is slower, and fresh fruit ripens more slowly.

Coffee plants also grow best at an angle of about 9°, within the range found on the lower slopes of most erupting volcanoes (6 to 10°). The volcanic terrain, in general, also provides enough shade to protect the coffee plants from the sun’s intense heat, which can cause poor growth.

Although Andisols are found globally around active and dormant volcanoes, climate control over coffee plant growth means that farming occurs mainly in the intertropical region zone around the equator, known as the “Coffee belt”.

The region extends into Central, South America and the Caribbean, as well as parts of Africa, the Middle East and Asia. Many major coffee-producing countries (such as Colombia, Costa Rica, Ethiopia, Guatemala and Indonesia) are found in this region and are closely linked to volcanic activity.


Coffee farming in volcanic soil: high risk


Most of the Andisols used for farming are found close to erupting volcanoes. The nature of these eruptions creates potential dangers. As well as ash clouds, explosive eruptions can produce hot streams of gas and ash, known as pyroclastic flows, and volcanic mudflows, known as outflows.

Both pyroclastic flows and outflows can reach speeds of more than 80 kilometers per hour and can travel tens or even hundreds of kilometers. When a volcano erupts, they sweep down the side in minutes and destroy almost everything in its path.

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Both hazards bring volcanic material to the surrounding area that, over time, will produce and sustain Andisols. However, in the short term, they can wreak havoc on farmland and wipe out entire towns.

Andisols encourage population growth around active volcanoes and previously unsafe volcanic areas. But as more people settle or farm near volcanoes, the risks to lives and livelihoods increase. This challenge will always exist.

Over the centuries, both experience and research have shown conditions affecting coffee plants’ growth. However, how each individual factor affects the taste of coffee is much more complicated. Small changes in local soil properties and environmental factors (terrior) can produce coffee with very different characteristics, even from coffee from nearby farms. While our understanding continues to grow, more research is still needed to assess how volcanic materials affect coffee flavor.

So the next time you sip a delicious cup of coffee from a famous volcanic region, think about the natural resources that helped create that unique flavor. Don’t forget to think about the coffee farmers who work in these dangerous volcanic regions daily to provide you with a distinctly different taste for your morning coffee.

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