Durian & Boron – How Much and When?
Always a great surprise for everyone in the office when a customer sends freshly harvested Durian. At retail prices of up to 1,000 Baht per kg, Durian can be very fruitful for the farmer as well.
A lot of farmers ask, how much boron should I use and when should I apply? It can be a complex answer without doing a complete soil test.
Good soil levels of available Boron are between 1.00 – 2.0 ppm and are deficient below 0.70 ppm. Due to the toxic nature of Boron and the fact that it is very mobile in the soil, raising soil levels of Boron can be tricky.
For mature durian trees (over 5 years) we recommend 1.6 - 2.4 kg per rai per year (80 - 120 g per tree) of Granubor® or Fertibor®, both of which contain 15% water soluble boron. Apply at the post-harvest and vegetative phases before flowering.
We also recommend using 200 grams of Solubor® (20.5% B) per rai as a foliar application up to four times during the growing season at the post-harvest, vegetative, and flowering stages. Solubor can be mixed and applied at the same time as your insecticide/fungicide.
“Even though soil and leaf tissue analysis usually show no B deficiency, fruit trees often have difficulty in transporting enough B to new flower buds,” says Dr. Timothy Righetti. “B is especially immobile in most plant tissues and will not readily move from other parts of the tree to the buds when it is needed for pollen tube growth, pollen production and other reproductive functions.”
“Under cool or otherwise poor growing conditions, flowers can deteriorate before fertilization is complete,” says Righetti. “Foliar B enhances fruit set in these situations by accelerating the fertilization process.” (‘Fruit tree foliar nutrient sprays’, RTM, U.S. Borax)
Some General Tips About Boron:
Many fertilizers and soil amendments contain boron and are a great way to ensure even distribution in the field. Be sure to ask about the B content as it may not be listed on the label.
Boron rates of application may need to be adjusted if you are applying with Lime or Dolomite.
Boron rates will vary based on the age of the tree. Fruit-bearing trees will require more boron.
Annual applications of boron are required as B is very mobile in the soil and immobile in the plant. Deficiencies will show up in new leaves and affect fruit quality, shape, and yield.
While Calcium puts the starch into the leaves, boron takes the starch out of the leaves and puts it into the fruit improving quality and size.
Good levels of organic matter and microbial activity will help with boron availability. Excess potassium in the soil will tie up boron.
Never use more than the recommended amount of Boron. Always consult your local agronomist for more information.