The term 'terroir' comes from the French and their affliction with wine. It is what the place gives the plant and encompasses the geographic, geological and climatic conditions that will impart unique characteristics to the product. It’s a term that is being used with high-end cocoa, hops, grapes, coffee and marijuana.

Just as Champagne claims to have particular terroir attributes that can make you uniquely tipsy, estates in Tarrazu, Heliodora, Antigua and many other regions make claims for their coffees based on their shared topography, altitude, soil type and surrounding vegetation: our grass is greener, so buy us.

The topography may contribute to the flavours by forcing a predominant wind direction, or by proximity to mountains and lakes. The lay of the land may lead to natural runoff of excess water or may force a particular micro-climate around the plants. The climate is determined in part by the local topography, but also surrounding vegetation, distance from the ocean, altitude...

Soil type is greatly dependent on plate tectonics and former vegetation: if the land once sat below the ocean and had a great mass of sediment pressing upon it, it would have a very different mineral composition from land formed from recent volcanic activity.

Shade

Shade is most important for the development of coffee at lower levels where the temperatures are higher. Coffee that is grown in areas that get a lot of cloud or in cooler areas/higher heights don’t actually benefit so much from shade. Here the greatest benefit of shade is not the flavours in your brew, but the additional habitat for birds and insects that may continue to cohabit with the coffee.

Altitude

Coffee is commonly considered better if the altitude is higher. However, it’s the temperatures that are important, rather than the air pressure. Arabica grows best at 15ºC-25ºC (59ºF-77ºF). It can grow outside this range, but will be severely damaged at temperatures below freezing. Generally the best temperatures are found at altitudes of around 1000 m around the equator, descending to sea level at around 23º latitude. Even this rule is rough: I’ve roasted and drunk coffee grown on the Galapagos island of San Cristóbal at 0.8ºS and an altitude of 140-360 m that was delicious. Some excellent coffee is grown in Hawaii at 19–21°N grown at 0-610 m. In both islands, the microclimate creates the right environment for growing quality coffee.

Soil nutrition

Most studies on nutrient deficiency have focussed on the health and yield of the plants and assumed that a healthy plant means good tasting coffee. Considering the coffee that the researchers were likely drinking, that’s a generous assumption. Many papers show that deficiency in any nutrient will hinder yield. Fewer papers have gone as far as using speciality coffee and polishing the cupping spoon.

Some recent papers have looked at the affect of nutrients on cup quality. However, much of the research is conflicting and seems to be site specific suggesting that the relationship between the nutrient availability and the cup quality is a complex relationship. These papers tease out correlations, but none of the research really pulls out enough to establish a causal relationship. The current and available research suggests there are more important things for the cup quality than proximity to a volcano.

In 1997 the Kenya Coffee Research Foundation added phosphoric acid to Colombian coffees in similar levels to that present in SL28. They found that the Colombian coffees mimicked the sweetness and many of the flavour characteristics of the SL28 varietal, Kenyan coffees.

Fertiliser

Coffee evolved in natural forest habitats with the leaf litter of other plants supplying the necessary nutrients for it to thrive. The shade conditions prevented excessive flowering, which meant it didn’t evolve the ability to shed excessive fruit load as many other perennial woody plants do. In times of drought, when most plants abort their fruit growth, coffee plants just keep growing the cherries, depleting the tree’s reserves, and deal with the consequences next year. In order to cope with the unnatural quantities of fruit that commercially grown trees produce and the loss of nutrients from the harvested cherries they need extra nutrients provided by fertiliser.

Plants take their nutrients from the soil. They don’t discriminate between mulched cherry pulp and leaves or commercial fertiliser. We might fret about how organic something is, but plants just need nitrogen in the form of NH4+ or NO3- and research suggesting that they prefer the owner’s manure to bags of fertiliser is inconclusive. There is, however, research that suggests that using organic fertiliser favours various microorganisms, which help to control root disease and increased bean size. Then again, use of mulch can also lead to a potassium/magnesium imbalance that can lead to a loss of acidity in the brewed coffee.

To get 1000 kg of green coffee beans, we produce 2700 kg of cherry pulp, which can be used as organic fertiliser. However, that same 2700 kg could be provided using 70 kg of commercial fertiliser. Although the organic fertiliser is available and free, the application isn’t. It’s much cheaper and quicker to pay someone to scatter 70 kg of granules, than get the people and equipment to compost and spread 2700 kg of mulch.

In irrigated crops, it’s possible to add fluid fertiliser to the system in a process termed 'fertigation'. The dissolved nutrients can be immediately taken up by the trees and can be easily applied over vast areas.

Commercial fertiliser also has its problems. Many farmers who saw the light and began using commercial fertiliser pre-2006, saw red when the price rose 100% 2006 to 2008. The ingredients of the fertiliser bags are subject to the same commodity fluctuations as the price of coffee and a farmer buying fertiliser and selling coffee has exposed herself to both.

Excessive use of fertilisers may negatively affect the flavour of the coffee - excess potassium may lead to harder beverages and too much nitrogen leads to bitter coffee.

According to Van der Vossen (2005), coffee production systems can only be ecologically sustainable if nutrients are replaced by a combination of organic and inorganic fertilisers.

Fertiliser is unlikely to be a health issue for us drinkers. If you’re looking for something to fear from coffee, you’re better off looking at insecticides.

Insecticides, fungicides, homicides

Due in a large part to inbreeding worse than the Saudi Royal family, coffee has been hit hard by pests and disease.

Caffeine is an insecticide. It’s not dangerous to humans except at very high doses and instead has positive physiological results. Despite this inherent insecticide, more than 900 species of pests attack coffee. Most originate in Africa and that’s where they’ve stayed. Some originate in the countries where they’ve been introduced and the majority of pests that have spread out throughout the coffee growing world got there with the shipping of green beans.

Pests and diseases damage the roots systems, trees, flowers and cherries and may cause the death of the tree, reduced yield and impaired coffee quality. ISO 10470: 2004 defines three classes of defect resulting from pests and disease and as these add up, the farmer’s earnings subtract.

The most important pests and diseases that damage the fruit are: coffee berry borer (CBB), coffee berry disease (CBD) and the Antestia bug.

Coffee berry borer

Originally from Africa, the CBB has spread throughout the coffee growing world except Papua New Guinea and Nepal . The female will enter a cherry and bore into the seed where it will lay an average of 74 eggs. Once hatched, the hungry little larvae eat through the seeds and mate with their siblings inside the berry. The holes left by the CBBs are often infected by bacteria and fungi. The bored berries weigh less, reduce the grade of the beans and adversely affect the flavour of the roasted beans. The ICO reckons that CBB costs farmers USD 0.5 billion every year.

Coffee berry disease

CBD is a fungus that causes cherries to drop early if it infects the tree at an early stage during the berry cycle. Although it is currently limited to Africa, it is likely to have a severe impact on high grown coffee if it manages to spread there.

Antestia bug

Antestia bugs feed by piercing the cherry skin, this provide access for fungi and bacteria leading to rotten beans (floaters), brown beans and black or partially black beans. The Antestia bug is the likely transmitter of the bacterium behind the potato blight that affects many Rwandan and Burundian coffees.

Coffee leaf rust

There are many diseases that indirectly affect the production and flavour of coffee by attacking the roots, flowers, leaves and trunk of the tree. Of these the most important is coffee leaf rust (CLR).

CLR is caused by a fungus. It infects leaves and often causes them to fall. In moderate cases, the resulting fall in energy supplied by fewer leaves restricts the growth of new stems and subsequent crop yield will decline. The weakened tree is also more susceptible to secondary diseases. When too many leaves fall, the leaf to cherry ratio is too small to supply the appropriate nutrients to the cherries leading to poor cup quality and possibly causing the cherries to drop.

In severe cases CLR causes overbearing dieback where the plant sacrifices roots and shoots in order to continue supplying the cherries with the nutrients they need. Repeated dieback will kill the tree, but the crop may become uneconomical for the farmer long before then.

Crops in Sri Lanka were wiped out in the late 1800s resulting in supplanting with tea. Farmers have attempted to bred cultivars to be resistant to CLR. The Kents cultivar was introduced into India and Africa and worked well for a while. However, the fungus mutated and new virulent strains attacked the formerly resistant Kents cultivars in Africa. Many attempts have been made to breed resistant coffee resulting in numerous cultivars. However, these plants are not bred for their hints of candied apricot and sugarcane sweetness. One of the problems for the speciality industry is that many CLR resistant cultivars are poor cupping cousins to the more susceptible varietals they replace. The supplanting of SL28 in Kenya with Ruiru 11 is a prime example of this.

An excellent resource for all things pestilent and disease inducing is: here.

Pest and disease management

'Management' in this heading sounds like a euphemism for killing, but predators and parasites are part of the natural cycle of things and can be ‘managed’ without extreme prejudice. Pests are flora and fauna that conflict with our interests. Michael and Tina Gehrken’s excellent plantation in Tanzania is proud home to several prides of lions, a babbage of elephants, a trash of buffalo and a zoo of other animals. A leopard, with a serious case of the munchies, once killed and stole his pet doberman from the kitchen and disembowelled his horse. Despite all that, he produces great coffee from his Blackburn Estate. Plantations and fauna can co-exist. There’s even space for pests in limited numbers.

One of the problems with blanket spraying of poisons is the ‘collatoral damage’ of the natural enemies of pests, which may make populations more vulnerable to future attack. Poisons have a place in management of pests, but use of shade, trapping, parasites and predators are also methods of control that don’t risk residue and are less likely to upset the biological balance.

  Coffee berry borer trap using water, honey and alcohol. Wahana Estate, Indonesia.

Coffee berry borer trap using water, honey and alcohol. Wahana Estate, Indonesia.

Pesticides generally improve coffee quality by eradicating pests that would damage the crop. However, some pesticides can get into the coffee beans and may also affect the flavours of the coffee. Organochlorine pesticides that were used to control CBB have been banned due to potential toxic residues in the beans and the damage to the environment. The greatest fear of consumers concerning poisons is that they will be absorbed by the coffee beans and splash into the cup that they’re drinking.

It’s hard to quantify the affect that terroir has on the flavour of the plant. Taken to an extreme, feeding a plant clay in a basement without light will somewhat stunt its opportunities to thrive. Terroir, as a term, is broadening to include the varietals used and what happens at the farm after harvest. But I prefer to keep the distinction and refer to the post-harvest as processing.