Effective Measures and Key Technical Points for Controlling Shoots and Promoting Flowering in Longan
Measures for Controlling Shoots and Promoting Flowering in Longan
1. Timely pruning
If one uniform autumn flush is planned, pruning after harvest should be slightly delayed, and can be carried out about 10-15 days after fruit harvest when the branches begin to sprout. Bearing branches should not be heavily renewed by cutting back; more leaves should be retained to help restore tree vigor. If two autumn flushes are planned, pruning should be carried out immediately after fruit harvest to promote early sprouting, growth and maturation of the autumn flush.
2. Fertilization to promote shoots
(1) Shoot-pushing fertilizer
Apply when each new flush begins to sprout, mainly nitrogen fertilizer, with an appropriate amount of phosphorus and potassium fertilizer. Based on a yield of 50 kg of fruit per tree, apply 0.50-0.75 kg each of urea and imported compound fertilizer per tree.
(2) Shoot-strengthening fertilizer
Apply when the new flush has basically stopped elongating and the leaves turn green, mainly phosphorus and potassium fertilizer. Based on a yield of 50 kg of fruit per tree, apply 0.50-0.75 kg of potassium sulfate and 0.25-0.50 kg of imported compound fertilizer per tree. Apply in a ring-shaped trench opened below the canopy drip line or in 4-6 radial trenches dug under the canopy.
(3) Foliar topdressing
Spray 0.3% monopotassium phosphate + 0.2% urea or Jindaduo 800 times foliar fertilizer, once every 5-7 days, for 2-3 consecutive sprays, to promote the autumn flush to mature and fill out within the planned time.
3. Preventing winter flush emergence and promoting flower bud differentiation
(1) Restricting fertilizer and water
Control the amount of nitrogen fertilizer in late autumn and winter. For spraying hormones to kill winter flushes, winter flushes that sprout from late November to early December must be killed before the buds reach 5 cm, using 1.0%-1.5% urea solution or 500-600 mg/L ethephon, spraying only the tender shoots and not the old leaves.
(2) Manual shoot removal
Removing longan winter flushes mainly refers to early winter flushes, or removing the leaves on winter flushes. This is generally done in early to mid-December.
(3) Tree injury to promote flowering
For relatively vigorous bearing trees, after the last flush matures, in early December use tree injury measures such as girdling, ring barking, root cutting and root exposure, combined with spraying foliar fertilizer containing phosphorus, potassium and trace elements, to increase nutrient accumulation in the branches and shoots and promote flower bud differentiation.
(4) Girdling and ring barking techniques
Generally, make 1 to 1.5 girdling rings on secondary or tertiary branches, or use half-moon or closed ring barking, with the depth reaching the xylem without damaging the xylem.
(5) Root cutting and root exposure techniques
Before winter flushes sprout, lime can be broadcast on the tree basin, 0.5-1 kg per tree, and the surface soil can be turned 15-20 cm deep inside and outside the canopy drip line to cut and expose roots.
Through tree injury techniques, vegetative growth of the tree can be reduced and water absorption decreased, thereby inhibiting winter flush emergence. Use with caution on weak trees and poorly managed orchards, and choose only one of the aboveground or belowground measures to avoid excessive tree injury. Tree vigor is weakened.
(6) Spraying shoot-control and flower-promoting chemicals
In early and mid-December, spray once each time with 40% ethephon at 300 mg/L. When spraying, wet the leaf surface only; do not spray until the leaf surface is so wet that it drips, so as to avoid an excessive dose causing heavy leaf drop. Do not spray weak trees or old trees. Alternatively, spray flower-regulating agent twice during the same period, using a concentration of 10 mL of flower-regulating agent mixed with 12.5-15.0 kg of water. After early to mid-January, choose 3000 times Aiduoshou solution + 0.15% glucose mixed solution, or choose 2000 times cytokinin solution, spraying once every 7-10 days for 2-3 consecutive sprays, to promote flower bud formation.
4. Applying flower-pushing fertilizer
(1) Flower bud differentiation fertilizer
Around the Winter Solstice, apply 25-30 kg of farmyard manure, 1.0-1.5 kg of calcium magnesium phosphate fertilizer and 0.5-1.0 kg of potassium fertilizer per tree.
(2) Flower-strengthening fertilizer
Around the Beginning of Spring, apply 0.25-0.50 kg of imported compound fertilizer, 0.5-1.0 kg of potassium sulfate and 0.25-0.50 kg of urea per tree.
If one uniform autumn flush is planned, pruning after harvest should be slightly delayed, and can be carried out about 10-15 days after fruit harvest when the branches begin to sprout. Bearing branches should not be heavily renewed by cutting back; more leaves should be retained to help restore tree vigor. If two autumn flushes are planned, pruning should be carried out immediately after fruit harvest to promote early sprouting, growth and maturation of the autumn flush.
2. Fertilization to promote shoots
(1) Shoot-pushing fertilizer
Apply when each new flush begins to sprout, mainly nitrogen fertilizer, with an appropriate amount of phosphorus and potassium fertilizer. Based on a yield of 50 kg of fruit per tree, apply 0.50-0.75 kg each of urea and imported compound fertilizer per tree.
(2) Shoot-strengthening fertilizer
Apply when the new flush has basically stopped elongating and the leaves turn green, mainly phosphorus and potassium fertilizer. Based on a yield of 50 kg of fruit per tree, apply 0.50-0.75 kg of potassium sulfate and 0.25-0.50 kg of imported compound fertilizer per tree. Apply in a ring-shaped trench opened below the canopy drip line or in 4-6 radial trenches dug under the canopy.
(3) Foliar topdressing
Spray 0.3% monopotassium phosphate + 0.2% urea or Jindaduo 800 times foliar fertilizer, once every 5-7 days, for 2-3 consecutive sprays, to promote the autumn flush to mature and fill out within the planned time.
3. Preventing winter flush emergence and promoting flower bud differentiation
(1) Restricting fertilizer and water
Control the amount of nitrogen fertilizer in late autumn and winter. For spraying hormones to kill winter flushes, winter flushes that sprout from late November to early December must be killed before the buds reach 5 cm, using 1.0%-1.5% urea solution or 500-600 mg/L ethephon, spraying only the tender shoots and not the old leaves.
(2) Manual shoot removal
Removing longan winter flushes mainly refers to early winter flushes, or removing the leaves on winter flushes. This is generally done in early to mid-December.
(3) Tree injury to promote flowering
For relatively vigorous bearing trees, after the last flush matures, in early December use tree injury measures such as girdling, ring barking, root cutting and root exposure, combined with spraying foliar fertilizer containing phosphorus, potassium and trace elements, to increase nutrient accumulation in the branches and shoots and promote flower bud differentiation.
(4) Girdling and ring barking techniques
Generally, make 1 to 1.5 girdling rings on secondary or tertiary branches, or use half-moon or closed ring barking, with the depth reaching the xylem without damaging the xylem.
(5) Root cutting and root exposure techniques
Before winter flushes sprout, lime can be broadcast on the tree basin, 0.5-1 kg per tree, and the surface soil can be turned 15-20 cm deep inside and outside the canopy drip line to cut and expose roots.
Through tree injury techniques, vegetative growth of the tree can be reduced and water absorption decreased, thereby inhibiting winter flush emergence. Use with caution on weak trees and poorly managed orchards, and choose only one of the aboveground or belowground measures to avoid excessive tree injury. Tree vigor is weakened.
(6) Spraying shoot-control and flower-promoting chemicals
In early and mid-December, spray once each time with 40% ethephon at 300 mg/L. When spraying, wet the leaf surface only; do not spray until the leaf surface is so wet that it drips, so as to avoid an excessive dose causing heavy leaf drop. Do not spray weak trees or old trees. Alternatively, spray flower-regulating agent twice during the same period, using a concentration of 10 mL of flower-regulating agent mixed with 12.5-15.0 kg of water. After early to mid-January, choose 3000 times Aiduoshou solution + 0.15% glucose mixed solution, or choose 2000 times cytokinin solution, spraying once every 7-10 days for 2-3 consecutive sprays, to promote flower bud formation.
4. Applying flower-pushing fertilizer
(1) Flower bud differentiation fertilizer
Around the Winter Solstice, apply 25-30 kg of farmyard manure, 1.0-1.5 kg of calcium magnesium phosphate fertilizer and 0.5-1.0 kg of potassium fertilizer per tree.
(2) Flower-strengthening fertilizer
Around the Beginning of Spring, apply 0.25-0.50 kg of imported compound fertilizer, 0.5-1.0 kg of potassium sulfate and 0.25-0.50 kg of urea per tree.