Many coffee farmers feel unsure about how to correctly mix and apply single-component (straight) fertilizers to their coffee fields. Although they know that coffee trees require different nutrients at different growth stages, they are often uncertain about the proper ratios.
In Vietnam, over 90% of the coffee area is planted with Robusta. Compared with other Robusta-producing countries such as Indonesia, Côte d’Ivoire, India, and Papua New Guinea, Vietnam’s yields are very high—often 4–5 tons of green beans per hectare. This means the amount of nutrients that must be returned to the soil is also very large. The following guidelines summarize expert recommendations for calculating and mixing straight fertilizers:
1. Guidance from Assoc. Prof. Dr. Phan Quốc Sủng – Director of the Vietnam Coffee Research Institute
Table of Contents
For mature, producing coffee trees:
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Apply 200 kg N + 150 kg P + 200 kg K per hectare per year to maintain an average yield of 2 tons/ha.
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For every additional 1 ton/ha of yield above that, add +70 kg N +20 kg P +90 kg K per hectare.
Examples:
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For 4 tons/ha, apply 340 kg N +190 kg P +380 kg K per year.
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For 5 tons/ha, apply 410 kg N +210 kg P +470 kg K per year.
2. Data from Malavolta (1990) on Indonesian Robusta (Saleh 1983)
At a yield of 1.5–2 tons/ha, coffee plants absorb roughly:
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53.2 kg N, 10.5 kg P, 80.7 kg K from the soil.
That is about 30.4 kg N, 6 kg P, 46.1 kg K per ton of beans.
With an estimated 40% fertilizer-use efficiency, each ton of beans requires:
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76 kg N +15 kg P +115 kg K supplied as fertilizer.
Examples:
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4 tons/ha: 304 kg N +60 kg P +460 kg K.
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5 tons/ha: 380 kg N +75 kg P +575 kg K.
3. Côte d’Ivoire Study (Snoeck 1983)
At 1 ton/ha yield, Robusta absorbs about:
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85.2 kg N, 17.6 kg P, 82.1 kg K.
With 40% efficiency, you must return roughly: -
213 kg N +44 kg P +205 kg K per ton.
Practical Recommendation
Considering all these studies and Vietnam’s higher yields, an acceptable reference range for straight fertilizer application per hectare per year is:
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Nitrogen (N): 300–400 kg
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Phosphorus (P): 150–200 kg
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Potassium (K): 400–500 kg
Notes:
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The K amount is typically about equal to or up to 1.2 times the N amount.
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P is usually less than half the N amount.
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Because these are high fertilizer rates, apply in several split doses. Multiple smaller applications reduce plant stress and improve nutrient uptake.
These figures give farmers a basis for calculating and mixing straight fertilizers according to the actual yield and soil fertility of their own coffee fields, helping them manage their coffee gardens more effectively and sustainably.