Technical solutions to restore durian trees after saline drought

After saline drought, durian trees often lose their leaves, burn their leaves, lose their roots and lose their ability to support fruit. Instructions for classifying the level of damage, washing salt slowly, restoring roots and leaves, cutting off excess fruit/branches and taking care of the tree in the first 60-90 days.

Summary: After the salinity drought, the most dangerous thing is the eagerness to "save the tree" by watering a lot and fertilizing strongly. The durian roots are weak at this time, the soil is still salty, the tree is easily shocked a second time. Restoration must go in this order: classify the level of damage, stop the salt source, gradually remove salt water when fresh water is available, reduce fruit/branch load, restore the roots and then restore the canopy.

Applies to: Durian orchards in the Mekong Delta are affected by drought, salinity or wrong watering.
Duration: The first 60-90 days after having a stable source of fresh water.
Difficulty level: Advanced. Be careful, do not do it all at once without classifying the trees.
Estimated additional costs: 5-20 million VND per hectare depending on the level of damage, recovery materials and care.

Classification of damage level

Before processing, divide the plants into three groups:

Light

Slight leaf edge burn.
The leaves are still green at over 70 percent of the canopy.
The tree has not shed many leaves yet.
The hairy roots are partly white or light yellow.

This group has good resilience if handled correctly.

Average

The leaves burn a lot, 30-50 percent fall.
Dried buds.
The plant wilts at noon, recovery is slow.
Few hairy roots, yellow brown.

This group needs strong offloading and root recovery first.

Heavy

Defoliation over 60 percent.
Dry branches, wrinkled bark.
Dark roots, bad smell or most of the hairy roots are missing.
The tree is bearing a lot of fruit but the leaves are no longer enough to feed.

The heavy group must prioritize saving the tree, not keeping the fruit.

Stop salting and check the water

Do not continue to take water from ditches/canals without measuring salinity.
Use an EC meter or suitable device to check the water source.
Close drains and embankments to prevent salt water from entering the orchard.
Only irrigate when there is a relatively stable source of fresh water.

Just because the water looks clear doesn't mean it's fresh. Durian has poor salt tolerance, so one more wrong watering can cause the tree to completely decline.

Wash the salt slowly

When there is fresh water:

Irrigate moderately to dissolve salt in the root zone.
Opens the drainage path so that water carries salt out of the tissues/lips.
Do not water around the base for a long time.
Many light repetitions are better than one too strong repetition.

If the soil is poorly drained, watering too much to wash away salt can cause root rot. Therefore, you must check the ditches and grooves before washing.

Reduce the load on trees

With a tree bearing fruit:

Light trees: prune small, distorted, diseased fruits.
Average trees: drastically reduce the number of fruits, only keep them if they still have enough leaves.
Heavy tree: remove the fruit to save the tree.

With branches:

Cut dry branches and severely burned branches.
Do not prune too hard at once if the tree is still weak.
Apply protection to large cuts.

Trees after drought and salinity do not have enough strength to both restore their roots and grow many fruits. Keeping the fruit at all costs often results in the loss of the tree.

Root recovery

After washing the salt and the soil started to feel fine:

Apply organic fertilizer around the edge of the canopy, not close to the base.
Add antagonistic microorganisms if the soil is no longer salty/waterlogged.
Water evenly, don't let it dry too quickly.
Do not apply heavy chemical fertilizers in the first 2-4 weeks.
A light dose of nutrients can be sprayed through the leaves to support when the roots have not recovered.

New roots are the foundation for recovery. The leaves may turn green temporarily after spraying, but if the roots do not recover, the tree will still decline.

Canopy restoration

When you see new hairy roots and the plant begins to sprout:

Apply balanced fertilizer in light doses, divided into several times.
Spray with micronutrients, aminos or seaweed if appropriate, do not overdo it.
Keep the canopy clear.
Prevent anthracnose and leaf blight on buds.

The first flush after drought is very important. If the buds are sick or lack water, the tree will take more time to recover.

Early flowering should not be treated

After drought, you should not force plants to flower immediately even if the price is good:

The tree needs to restore its leaves and roots.
Blooming treatment puts additional pressure on the plant.
If flowers bloom on weak trees, the drop rate is high, the fruit is poor and the tree declines.

Only count the crop after the tree has had at least 1-2 waves of healthy leaves, the roots have clearly recovered and there are no longer any lingering yellow leaves.

Common mistakes

Water heavily as soon as fresh water is available: if drainage is poor, the plant will become more waterlogged.

Use strong fertilizer to help plants grow quickly: weak roots can burn easily, salt in the soil is still high.

Keeping fruit on a failing tree: losing both fruit and tree.

Not measuring salinity: continue to water with the wrong salt water.

Forcing early flowering after recovery: the plant is not strong enough, there is a risk of losing the next crop.

Monitor and record

[ ] Salinity of water source each day/week.
[ ] Level of leaf loss and leaf scorch in each group of trees.
[ ] Salt washing day, number of washing times.
[ ] Number of fruits/branches removed.
[ ] The condition of hairy roots after 30-60 days.
[ ] The first batch of new leaves after recovery.

Recording groups of trees helps decide which trees to save, which trees need to be replaced, and which plots need to be renovated.