Introduction
Table of Contents
At the request of many readers in Vietnam’s Central Highlands, Y5Cafe is republishing this practical guide on diagnosing soil fertility to fertilize coffee efficiently and avoid waste. Despite market ups and downs, coffee remains the region’s dominant crop.
Many growers already know how to care for their coffee trees and achieve high yields—some robusta plantations consistently produce about 5 tons of green beans per hectare, ranking among the highest in the world. But in any intensive farming system, proper fertilization is key to stable and profitable yields.
Importance of Accurate Fertilization
To fertilize correctly, farmers must:
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Understand the crop’s nutrient needs.
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Supply the right nutrients in the right amounts.
This not only prevents waste but also improves fertilizer-use efficiency, ensuring long-term soil health and sustained coffee production.
Recommended Fertilizer Rates for Robusta Coffee
Long-term research by the Western Highlands Agro-Forestry Science and Technical Institute (WASI) recommends the following annual rates for mature robusta coffee:
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Nitrogen (N): 220–250 kg
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Phosphorus (P₂O₅): 80–100 kg
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Potassium (K₂O): 200–230 kg
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Sulfur (S): 40–60 kg
This equals approximately:
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430 kg urea
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250 kg ammonium sulfate (SA)
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600 kg fused phosphate
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380 kg potassium chloride (KCl) per hectare per year
These rates sustain yields of about 3 tons of green coffee per hectare. For each additional ton of yield beyond 3 tons, add about:
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150 kg urea
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120 kg fused phosphate
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120 kg KCl per hectare annually.
Why Soil Testing Is Essential
Because soil fertility differs by field, each plot should be tested to determine its actual nutrient levels and adjust fertilizer rates accordingly.
Recommended Testing Frequency
Farmers should test their soils every 3–4 years to update their fertilization plans and avoid nutrient imbalances.
Common Findings in Đắk Lắk
Recent soil tests show that many coffee fields already contain excessive phosphorus and potassium, yet growers often continue to apply high rates of these nutrients.
Risks of Over-Fertilizing:
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Excess phosphorus can cause zinc deficiency.
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Surplus potassium can limit magnesium uptake.
How to Collect Soil Samples?
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Select five points in a zigzag pattern across the coffee plot.
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At each point, at the edge of the coffee canopy, dig a small hole 30 cm deep.
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Use a knife to shave a thin vertical slice of soil from top to bottom; collect about 200 g.
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Mix soil from the five points into a single 1 kg sample to represent the plot.
Avoid sampling directly beneath large shade trees or areas recently fertilized. For commercial coffee with irrigation basins, take samples from the inner edge of the basin.
Where to Test and Cost
Farmers in the Central Highlands can bring samples to the Western Highlands Agro-Forestry Science and Technical Institute (Hòa Thắng commune, Buôn Ma Thuột City).
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Testing cost: about 100,000–150,000 VND—roughly the price of a single bag of fertilizer—
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Yet this small investment ensures the efficient use of hundreds of other fertilizer bags and protects long-term soil health.
Conclusion
By following a soil-diagnosis-based fertilization plan, coffee farmers in Vietnam’s Central Highlands can improve fertilizer efficiency, reduce waste, and maintain sustainable, high-yield production. Regular soil testing is a simple, cost-effective step toward long-term profitability and environmental protection.