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Soil plays key role in coffee cultivation

The type of soil in which coffee plants are grown plays a central role in the cultivation of high-quality beans.

A number of factors relating to the earth come into play when determining the success, quality and flavour of crops, and these all have a bearing on the metabolism of coffee trees.

The ideal soil conditions for cultivating coffee are believed to be fertile and well-draining, including volcanic red earth and deep, sandy loam.

Conversely, those that provide a hostile environment for coffee plants are poor draining like heavy clay and soil with a low pH, the latter of which can restrict yields.

The right soil conditions are essential to successful cultivation

The Food and Agriculture Organization (FAO) of the United Nations recommends: "If a coffee tree is to grow well, it needs more than anything else a soil of good structure, permeable and deep."

It notes the depth of soil is essential to allow roots to grow and the soil structure needs to be favourable to enable them to penetrate it, with processes such as mulching or cultivating cover crops ensuring soil is not left bare and at risk of erosion.

Furthermore, the FAO adds that it is important to water soil regularly to ensure it remains moist for growing coffee plants.

Soil erosion, surface run-off and leaching can all pose threats to a successful and high-quality coffee crop by harming soil fertility, causing organic matter to decline and affecting water sources.

There are various ways of employing effective soil management techniques in order to reduce such problems and responsible tillage management can ensure soil surface and organic matter are safeguarded.

Scientists identify correlation between soil and cup quality

Research into the influence of soil properties on the quality of Arabica coffee carried out by experts in Germany and Ethiopia found that soil conditions played a role in the quality of beans from south-west Ethiopia.

A total of 74 sample plots in the Afromontane coffee rainforest ecosystem were used by the researchers, who discovered there was a site specific element in the effect of micronutrients on cup quality.

However, they also observed "the quality of the soil is a very important factor for the production of quality coffee, and specifically the balance between the different nutrients is of paramount importance".

Factors that were measured by the team from the University of Bonn and the Ethiopian Institute of Agricultural Research in Addis Ababa included pH values, and potassium, phosphorus, calcium and nitrogen levels.

Farmers can take steps to protect soil and improve quality

Monitoring soil conditions can provide coffee farmers with vital information that may be used to improve cup quality and yields.

For instance, recording soil pH in plantations provides a crucial indication of the biological and chemical health of the earth, with adjustments such as adding lime to soil potentially restoring a balanced pH and enabling crops to flourish.

In order to achieve an ideal environment for coffee to thrive, fertiliser often plays an important role for farmers seeking to improve soil quality, as it increases the amount of nutrients available to plants.

The International Coffee Organization notes that organic standards include soil conservation and maintenance of soil fertility, which can both contribute towards improved cultivation of coffee.

Using organic matter or cover crops can improve the quality of soil on coffee plantations, and ongoing management of pests and nutrients is required to ensure that a healthy environment is maintained.

For instance, agroforestry is a process by which coffee is grown in the shade of trees that can promote certain nutrients in the soil and provide a favourable microclimate for plants. Leaving crop residues in fields may improve quality, and reduce surface runoff and erosion.

The use of pesticides and chemical fertilisers can be beneficial for soil quality, but organisms other than those being targeted can be affected by them, and it is important to minimise water and air pollution when using such substances.