If you want to produce high-quality sitao that is sweeter than those you find in the market, you should listen to Danny Mateo, an award-winning farmer from Sulucan, Angat, Bulacan.
Danny swears that his sitao is sweeter than most varieties in the market because he applies enough potash (0-0-60) to his plants just when they start bearing flowers. You can apply 50 grams per hill. The potash should be buried in the soil because it is not readily absorbed by the roots if the fertilizer is just broadcast over the soil surface.
Simple, is it? Yeah, and you can easily do it.