Farmers are now entering the second round of watering to stimulate the second flush of coffee blossoms while at the same time nurturing the first set of developing fruit.
This is a critical and sensitive stage for the coffee tree, strongly affecting yield, bean quality, and how evenly the crop will ripen.
Pruning for Consistent Yields
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Dr. Tôn Nữ Tuấn Nam of the Western Highlands Agro-Forestry Science Institute explains that robusta coffee does not flower again on the same branch that fruited the previous year. Therefore, pruning is essential:
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Remove old, exhausted branches so that new fruiting shoots can emerge; these will carry next year’s blossoms.
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Cut away inner branches that are shaded and receive little sunlight.
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Thin the top canopy and very small shoots around the main trunk so that sunlight reaches all fruiting branches evenly.
Pruning right after harvest helps the tree channel nutrients into flower bud formation and ensures a good bloom.
Irrigation to Trigger Bloom
Watering is the key factor in controlling synchronized flowering and fruit set.
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The best time for the first irrigation is when the soil surface has dried and the coffee leaves begin to curl (first signs of wilting). At this point the tree has already formed flower buds, so adequate water will trigger a uniform bloom.
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Combine the first watering with fertilizer application to supply nutrients for heavy flowering and fruit set.
For the dry season, use a fast-dissolving fertilizer high in nitrogen and phosphorus but lower in potassium, for example NPK 20-5-6 + TE.
To support flower bud development, strengthen pollen vitality, increase fruit set and reduce fruit drop, spray a foliar fertilizer rich in phosphorus and boron, such as 30-10-10 + TE together with NaturBor.
The second irrigation is also applied when soil and leaves again show signs of dryness. Apply about half to two-thirds of the required water first so it soaks deeply, then broadcast the fertilizer and apply the remaining water to carry nutrients down to the roots.
Practical Fertilizer Guidance
According to agronomist Trương Quốc Huy (Binh Điền Fertilizer Co.), the recommended product for the dry season is Đầu Trâu Dry-Season NPK 20-5-6 + TE.
In some years, despite irrigation, coffee does not flower normally. Dr. Tuấn Nam notes that in the 2011 dry season cooler temperatures and fewer sunny days delayed soil drying. Farmers who irrigated by calendar date rather than by observing soil and plant conditions watered too early, before the buds were ready. Always base irrigation on field observation, not just the calendar.
Other Important Notes
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Some growers in Gia Lai hoe the soil surface inside the irrigation basin (5–6 cm deep) to speed drying before watering, forcing a stronger bloom. This may cut fine feeder roots, speeding drying and triggering abundant flowers, but it injures the roots, reduces nutrient uptake for fruit filling, and increases susceptibility to pests and diseases. It may help for one season but harms the next.
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Coffee on basalt soils (pH about 4.5) needs lime. Apply about 0.5 kg of lime per tree every two years to reduce soil acidity and to help control pests and root-boring insects. Buy lime or fertilizers only from reputable dealers and check quality if purchasing from mobile vendors.
Large Fruit but Small Beans
If only a few trees show this problem it is usually genetic (poor variety). If the whole plantation is affected, the cause is imbalanced fertilization:
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At the start of the rainy season, coffee fruit volume expands rapidly—lack of nitrogen at this stage results in small beans.
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At the end of the rainy season the beans accumulate dry matter—if potassium is deficient and nitrogen is excessive, fruits retain too much water, producing large cherries with small beans.
Secondary and trace element deficiencies can also increase the proportion of “peaberries” (single-seeded cherries).
Fertilizer Rates for High Yields
To achieve 3–4 tons of green beans per hectare, apply about 200–400 kg of Đầu Trâu Dry-Season fertilizer and 1,500–1,700 kg of NPK 16-8-16 + TE Đầu Trâu during the rainy season. For yields above 4 tons/ha, increase total fertilizer by roughly 1 ton for each additional ton of beans expected.
Pest Control
To control ants, some farmers mix ant poison with grease and smear it on trunks. According to agronomist Nguyễn Hoàng Bảo (Syngenta), this wounds the bark and encourages canker disease.
The safer method is to dilute the ant poison in water and spray only localized nests. Do not eradicate all ants—maintaining some ants helps keep cicadas and other pests in check and preserves ecological balance.