Conditions in Da Lat: cold nights can reduce nutrient uptake

During operation of hydroponic vegetable farms in Da Lat, several recurring conditions can be observed:

• Nighttime air temperatures frequently fall below 13°C.
• Nutrient-solution temperature can fall below 16°C.
• Extended rainy periods can keep the solution cold for several consecutive days.

At these temperatures, plant roots can face significant problems:

• Root enzyme activity decreases.
• Uptake of N, P, K, Ca, and Mg is noticeably reduced.
• Roots grow more slowly and may become darker, shorter, and develop fewer root hairs.

Plants may show slow growth, pale leaves, calcium-related leaf-edge burn, and greater susceptibility to root disease during prolonged cold periods. These factors can make yield less predictable, extend harvest cycles, and reduce crop consistency.

Observed data: daily temperature variation

Seven-day monitoring showed air temperature dropping from approximately 18–20°C during the day to 11–13°C at night. Nutrient-solution temperature changed more slowly but tended to remain below the optimal range throughout the night.

For many leafy vegetables, a typical target range for nutrient solution is 18–22°C. When solution temperature drops below 16°C, nutrient uptake can become very limited even when nutrient concentration remains sufficient.

Solution: heating the hydroponic solution at night

UTEK deploys a dedicated nutrient-solution heating system designed for Da Lat's climate.

Operating principle

• A sensor continuously measures solution temperature.
• When temperature falls below a configured threshold, such as 18°C, the heating system starts automatically.
• The system maintains a stable temperature through the night while minimizing sudden temperature changes around the roots.

Key features of the UTEK heating system

• Even heating to minimize localized hot spots.
• Two-layer over-temperature protection for the nutrient solution.
• Electrical leakage protection for safer operation in humid environments.
• Fully automatic operation without routine manual intervention.
• Energy-conscious operation during nighttime hours.

Observed results at the Da Lat farm

After applying nutrient-solution temperature control, the farm observed:

• Whiter, longer roots with more root hairs.
• Improved nighttime nutrient uptake.
• Growth rates reported to be 10–20% faster than before.
• Thicker, darker green leaves and greater consistency between trays.
• Lower incidence of root problems during cold periods.

More importantly, the growing cycle became more predictable, helping the farm estimate harvest dates and plan market supply more effectively.

Conclusion

Under Da Lat's climate conditions, hydroponic nutrient-solution temperature control is a critical operating factor for stable and efficient production. UTEK's solution-heating system addresses one of the main constraints of cold-night hydroponics and helps plants maintain more consistent growth, nutrient uptake, yield, and quality throughout the year.