COIROLOGY JOURNAL · Plant nutrition

NPK and coir: building a feeding programme

Coir provides a growing medium, not a complete diet. NPK is part of plant nutrition, but a suitable programme also considers other nutrients, water and the crop.

15 October 20242 min read

NPK illustration, not an application-rate recommendation.

What N, P and K describe

Nitrogen, phosphorus and potassium are essential plant nutrients. Nitrogen is involved in proteins and chlorophyll, phosphorus in energy transfer and other cellular functions, and potassium in processes including water regulation.

They are not the only essential elements. Calcium, magnesium, sulphur and micronutrients also belong in an appropriate nutrition programme.

Read the product and feed labels together

Establish whether the medium already contains fertiliser, and follow the directions for that specific product. A coir block should not be assumed to include a complete feed.

Choose a nutrient product intended for your crop and growing method. An NPK ratio on its own does not establish the right dose, nutrient forms or completeness of the formulation.

Account for the water supply

Irrigation water contributes to the chemical environment around the roots. In commercial production, water analysis is a useful part of designing and reviewing the programme.

Avoid a universal recipe that ignores source water, crop stage and the supplied substrate. Keep records of what is applied and when.

Understand what EC can tell you

EC reflects dissolved ions together. A higher reading does not prove that every nutrient is present in the right proportion, and a lower reading does not identify which nutrient may be lacking.

Where an imbalance is suspected, choose analysis that addresses the question. The coir chemistry article explains the distinction between soluble salts and exchangeable cations.

Respond to evidence

Look at growth, roots and management history before adding more feed. Several problems can produce similar symptoms, so changing multiple products at once can obscure the cause.

For a commercial investigation, SubstrateLab can help define the relevant testing scope. The nutrition reference below provides background; product instructions and crop-specific advice remain essential.