I got this tip from a local certified organic farmer and it should work very well for mangos as it did for all my bananas last year. I posted the following on bananas.org last Nov.
“OK ----- here it is. The solution to force a banana flower to push out earlier.
For you guys in California it's cheaper than for me. I had to pay $45.00 for shipping alone.
Peaceful Valley sells a Sulfate of Potash
product made by Diamond K. It only comes in 50 lb bags. To get the best fast result use the water soluble, ultra fines
version. It meets organic certification requirement.
Using a strainer, I apply 2 tablespoons around the near to fruiting size pstem on each mat -- followed by a second and final application a week later. Seems like a small dose --- that's because NPK is 0-0-50. That's it! It's a fine powder - just tap the strainer and you get a good even distribution of the powder. I put the powder in the strainer sitting on a paper plate to avoid loss. The strainer sits on the plate - not me!
All my fruiting height pstems have produced the flower in 1 to 4 weeks after the S of P sprinkle. Exception is the Pisang Klotek at 9.5 ft.
And that's not all ------ to maintain organic certification he only ferts his naners with Purdue chicken mix (with caiticin, sic, and yucca added by our local Ag supplier -- Diamond R). His appl rate is 2 cups per mat every 2 weeks from March till end of Nov. He uses it on everything from his grafted tomatoes, lettuces, chard, kale, papayas to his bananas, to name a few.
So I started to add the chicken mix (3-2-3) to my mats along with the non-organic 6-3-16. It also helps to bring the nitrogen up closer to K/2 for better K utilization.
Chicken mix breaks down slowly so I expect to see the full effect in next years production.
Here's a good pic of the 4 to 6 week early result-----------------