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T 3.04 Plant Nutrients and Fertilisers

‘Use of agro chemicals such as fertilizers, lime, biocides and growth inductors are common, which reaches up to 54% of the total costs for coffee production.’ (Sousa et al.,2012)

Plants are able to make their own food from sunlight and carbon dioxide (see Chapter 1.01, ‘Photosynthesis and Respiration’). However, in order to do so, they need a supply of certain nutrients from the soil. If any of these nutrients is lacking in the soil, it can limit plant growth and yield, even if the growing conditions are otherwise ideal.

Fertilising a plant means adding some of these nutrients to the soil in order to support plant growth, combat certain diseases, or to increase yield. Fertilisers can be naturally derived, such as manure or compost, or synthetic. Fertiliser use can have a dramatic effect on yield, and make otherwise unproductive soils suitable for farming, but can be damaging to the environment  – whether natural or synthetic – if their use is not carefully controlled.

This subject can be challenging for farmers. Fertilisers can come at considerable expense, and we have heard many reports of misinformation — in some cases even reports of counterfeit fertilisers being sold to farmers. This lesson is a summary of common inputs on coffee farms but the terroir of every region is different, so there is no universal cure-all.


Essential Elements

The coffee tree requires 16 essential elements for its proper nutrition. These can be divided into four groups, based on their function and importance.

Group 1: Carbon, oxygen, and hydrogen. These elements are present in water and air, and used by the plant in photosynthesis to create glucose.

Group 2: Nitrogen, phosphorus, and potassium (N, P, K). These are also called “macronutrients,” due to the large amount of them that healthy coffee trees need.

Group 3: Calcium, magnesium, and sulphur. These are called “secondary nutrients,” because they are needed in lesser amounts than the macronutrients.