Technical solutions for cultivating durian trees to cope with drought and salinity

Durian has poor salt tolerance, so orchards in the Mekong Delta need to prepare before the dry season. Instructions for storing fresh water, measuring salinity, bunds, root cabinets, reducing evaporation, adjusting crops and protecting roots when salinity drought comes.

Summary: With durian, coping with drought and salinity must be done before salinity enters the orchard. When trees have burned leaves, fallen leaves, or lost roots, recovery costs are very high. This article provides instructions on what needs to be done to prepare: storing fresh water, measuring salinity daily during the dry season, keeping soil moist, reducing evaporation, protecting orchard ditches and adjusting flowering and fruit growing schedules to avoid peak salinity periods.

Applies to: Durian orchards in the Mekong Delta, especially riverside areas, islands, and areas at risk of saltwater intrusion in the dry season.
Duration: Prepare 2-3 months before the dry season, monitor continuously during the salty season.
Difficulty level: Advanced. Need to proactively manage water, not waiting for salt water to enter before treating it.
Estimated additional costs: 10-100 million VND per hectare depending on investment level in reservoir, embankment, irrigation system and measuring equipment.

Response principles

Durian is a plant sensitive to salt. When the soil and irrigation water contain salt, the roots have difficulty absorbing water, and the plant experiences "physiological thirst" even though the soil is wet. Response principles:

Do not water with salty water.
Storage fresh water before it becomes salty.
Keep soil moist to reduce irrigation needs.
Good drainage when salty washing is needed.
Do not let the tree bear too much fruit during the salty season.

Don't rely on the feeling of tasting water. A salinity measuring device is required.

Prepare water

Store fresh water

Dredging ditches, ponds and lakes before the dry season.
Line or reinforce water storage areas if there is a lot of water loss.
Cover the water if possible to reduce evaporation.
Calculate the amount of water according to the number of trees and expected salinity time.

Salt measurement

Use a suitable EC pen or salinity meter.
Measure before pumping water into the ditch/orchard.
Measure many times a day if the tidal area is strong.
Record measurements to know when to turn on/off the water.

Canal water may be usable in the morning, but in the afternoon it will be salty. Not measuring is a big risk.

Embankments and culverts

Check the embankment before the dry season.
Reinforce leaks and low points.
Sluices must be closed when salinity rises.
Do not let salt water overflow into the orchard ditch.

The orchard already has an internal ditch, but if salt gets into the ditch, it is very difficult to quickly handle it, because the salt will seep into the tissue/drain.

Moisturizes and reduces evaporation

The base is made of straw, dry grass, coconut leaves, and clean materials; Leave the root collar intact.
Keep the grass low in the middle of the row if competition is not too strong.
Avoid strong pruning right before drought.
Spray leaves lightly when plants are stressed, do not overuse.
Drip/root irrigation to save water.

The goal is to reduce the amount of water plants need during periods of limited fresh water resources.

Seasonal adjustment

If the area often experiences peak salinity:

Avoid allowing trees to grow large fruits at times when salinity is severe.
Do not treat flowering when irrigation water sources are at risk.
Consider an off-season flowering schedule if it helps avoid salinity and the orchard is qualified.
The tree has just gone through a heavy crop so it should be rested, not pressed further.

Fruit trees need steady water. If there is a lack of fresh water during the fruit growing stage, fruit drop, wilting and tree failure all increase.

When the salinity drought is happening

Measure salt before every watering.
Irrigate sparingly, right at the root zone, do not over-water.
Prioritize water for fruit-bearing trees or high-value trees, but do not keep fruit on severely weakened trees.
Do not apply heavy chemical fertilizers when the soil is dry/salty.
Watch for leaves to burn at the edges, drop leaves, and wilt at noon.

If there is not enough fresh water, reducing fruit load and keeping trees alive must take priority over maintaining yield.

After having fresh water again

Wash salt slowly, combined with drainage.
Do not overwater for a long time.
Apply organic fertilizer and restore roots when the soil is stable.
Do not treat flowering immediately.
Classify trees for recovery according to damage level.

Incorrectly salting can cause plants to become waterlogged. If you want to remove salt, there must be a way for the salt to escape.

Common mistakes

Do not store water before the dry season: it will be too late to find water when the salinity rises.

Do not measure salinity: clear water can still harm plants.

Overwatering to save effort: wastes fresh water, increases root collar moisture.

Strong fertilization during drought: roots stress, poor absorption, easy root burn.

Keeping too much fruit when there is a lack of water: the tree will decline severely after the season.

Monitor and record

[ ] Water salinity by day.
[ ] Remaining water level.
[ ] Amount of water for each plot.
[ ] Leaf condition: burnt edges, falling off, wilting.
[ ] Number of fruits kept/cut off.
[ ] Starting date of salt washing and recovery.

This data helps prepare better for the next dry season, especially in saline areas that repeat for many years.