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Volcanic Rocks For Crops

By Sapphire Wanmer

Photo credit: Goldlocki, Wikimedia Commons [a]

Where our food comes from and what makes up the food that we eat seems to be a hot topic at the moment. In many volcanically active regions of the world volcanoes are essential to good harvests and larger scale crop production. In the UK we do not have any active volcanoes so what affect do volcanoes have on UK grown produce? And, how can volcanoes influence your diet?

There is an ever increasing demand for food and crops as population increases and the land available for agriculture decreases. Therefore it is becoming more and more important to grow lots of crops quickly to fill this demand, but this is not possible without a little helping hand from fertilisers. This is because as crops grow they use nutrients from the soil and when the crops are harvested these nutrients are removed and are no longer available in the soil for the next growth of crops. This leads to degradation of the soil quality which results in degradation of the quality of crop produced. By adding fertiliser to soil this allows nutrients to be available even if each growth of crops is harvested and removed from the land. In volcanically active regions volcanic ash can provide a long lasting, self-replenishing natural fertiliser. So what do volcanoes have to do with crop growing in the UK? After all, there are no active volcanoes in the UK.

A volcanic influence

To begin with a soil will contain a certain amount of nutrients and minerals depending on the underlying rocks. The geology beneath the soil can contribute to soil when the rocks are broken down, for example by dissolving in groundwater or by being broken up and added to the soil by burrowing organisms. Some rocks are better than others at providing the right nutrients and minerals for plant growth and volcanic rocks are amongst the best, therefore if an ancient volcano lies buried beneath the soil it may influence the nutrient and mineral intact of the plants in the soil above. Volcanic ash deposited on the surface of a soil can also have a beneficial effect making them more suitable for plant growth.

Somewhat artificially, finely ground grains of volcanic rock can be used as multi-nutrient silicate rock fertilisers [1]. These have the potential to be much more beneficial to agriculture as a fertiliser, for example in very sandy soils, as they contain a wider range of important nutrients than many commercially used fertilisers [1]. They are also suitable as they release nutrients and minerals gradually over time, this could mean that less fertiliser is required over time which could save costs for the grower. Although, in certain conditions and soil types the breakdown of the volcanic material might be too slow to be of any benefit.

Many volcanoes around the world are exploited for their wonderfully fertile soils, some of the food imported into the UK may well have originally grown at the foot of an active volcano. But with no active volcanoes in the UK how do volcanoes affect UK grown produce?

Volcanoes and agriculture in the UK

Throughout history the UK has been affected by volcanic eruptions occurring hundreds of miles away. For example the eruption of Laki, Iceland in 1783 pumped vast volumes of aerosols into the atmosphere that caused sulphuric acid to rain out across Europe damaging crops and vegetation. Volcanic eruptions in Iceland have also spread ash across the UK throughout history, most recently in 2010 due to the eruption of Eyjafallajokull. Although very fine, these small amounts of ash that may go un-noticed by you and I, can add a small amount of additional nutrients and minerals to soil all over the UK. The overall effect on our soils is incredibly small though. There is a gradual shift to the production of crops, including fruit and vegetables, from large out-door fields to growth and harvest in mega greenhouses, and this is where volcanoes can have a much greater affect.

Thanet Earth is Britainís largest greenhouse. It covers an area the size of ten football pitches and is home to more than 1.3 million plants which provides the UK market with tomatoes, peppers and cucumbers [2]. The strange thing about these crops is that they are grown hydroponically or without soil [2]. Instead of soil the crops take root in a volcanic rock wool. This rock wool is produced from basaltic rock which comes from volcanoes. The basalt is melted, then air is blown through it to make a candy-floss like wool made of volcanic rock [2]. The most beneficial part of using volcanic rock wool instead of soil is that it provides a greater stability for the plant [3] and this is seen as being more important than any potential minor nutrient or mineral benefits. There is no emphasis on the nutrient or mineral benefits of crop growth in volcanic materials at Thanet Earth because the conditions in which these plants are grown in do not allow for the normal breakdown and movement of nutrients and minerals from volcanic rocks as they would do in normal soils. Therefore in addition to being grown within a volcanic material the plants also need to be given extra nutrients to allow them to grow bigger quicker.


Volcanoes have an effect on the growth of crops here in the UK. The ancient volcanic rocks that underlie soils and the fresh addition of volcanic ash from eruptions in Iceland can provide essential nutrients and minerals for crop growth. This is in addition to new innovative agricultural techniques, such as those used at Thanet Earth, which mean that volcanic rocks are having a greater use in modern crop production in the UK today.


  1. Straaten, P.V. 2006. Farming with rocks and minerals: challenges and opportunities. (Accessed 30/11/2015).
  2. (Accessed 30/11/2015).
  3. (Accessed 30/11/20151).
  4. (Accessed 30/11/2015)

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