●The principle of increasing grape sugar content - Grape farming becomes easier when you know the principle. 1. Blockage of xylem - Most grapes have blocked xylems just before ripening. The branches of all grapes are composed of xylem and sieve tubes. ■Xylem - The part inside the branch that absorbs nutrients and water through the roots. ■Sieve tubes - The passageway that transports carbohydrates, which are assimilation products made in the grape leaves on the outside of the branch. In a normal grape growing process, the xylem closes before ripening, preventing the delivery of nutrients and water to the grapes. In other words, this means that water does not escape from the grapes. 2. Sugar content of grapes? - The sum total of sugars delivered by potassium (K+) outside the granules, which is delivered in exchange for the hydrogen ions (H-) produced during the malic acid decomposition process + the sugars created by the decomposition of ●malic acid● inside the granules. That is, in order for the sugar content to increase, it must be created before the fruit matures, and as it decomposes, a lot of sugar and hydrogen ions are created, and the amount of hydrogen (H-) ions must increase, so that the amount of potassium (K+) ions that transfer sugar increases, and the sugar content increases. What creates malic acid? - It is a carbohydrate (sugar), an assimilation product of photosynthesis. It plays an important role in reducing the consumption of nutrients stored from the previous year, which occurs due to excessive fruit setting or branch overgrowth during the growth process, and in creating new glucose through photosynthesis. That is why it is important to maintain thick, moist, and healthy leaves with clear veins, as I mentioned before. 3. Crisp grapes - During the discoloration period, the water vessels are blocked, but the nutrients created in the leaves are transferred to the grapes through the sieve tubes, so the soft grapes become hard again, giving them a crunchy texture. 4. Fertilizer management During this period, we recommend fertilizing with a focus on potassium and foliar fertilization with a focus on calcium and magnesium. Now, I also recommend foliar spraying of a growth inhibitor so that all the energy can go to the fruit. 2 cycles in the order of potassium sulfate - potassium sulfate - potassium phosphate ◇ Phosphoric acid - Fills the inside of the fruit with roots, flowers, and energy ◇ Potassium - Large fruit, increases sugar content... ◇ Calcium - Firms cell tissue, increases hardness of fruit ◇ Sulfur - Improves taste, aroma, and color ◇ Magnesium (potassium phosphate) - Improves leaf photosynthesis 5. Water management - After the softening period, I recommend afternoon irrigation even during the discoloration period. The situation will be slightly different for each farm, but I recommend that you manage the orchard to always maintain a moist state by giving a little water frequently rather than giving a lot at one-week intervals. I irrigate for 50 minutes every three days in the afternoon. And as I said, U-bi-mu-hwan, after the rainy season comes heat waves and tropical nights. It is a difficult time to increase sugar content. I hope you manage the leaves well and look forward to a bountiful harvest this year as well.