Irrigate right after planting, on the 3rd day, then weekly. Stop irrigation 15 days before pruning and 15 days before harvest. The source gives a drip schedule by growth stage, with most water during shoot growth and ripening. Nutrient needs vary with variety, vine age, soil and water — the source advises fertilizing based on soil, water and petiole tests. Too much nitrogen gives leafy growth and fewer bunches; phosphorus helps flower-bud formation; potash helps cane maturity and bunch quality.
Pending expert review
Source
Crop Production Guide – Horticulture Crops 2020 (Directorate of Horticulture and Plantation Crops, Tamil Nadu & Tamil Nadu Agricultural University (TNAU)), Grapes – Irrigation; manures and fertilizers, pp. 21–23
