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Grape Vineyard Water Use Calculator Background Discussion |
| Knowing the amount of water used by a grape vineyard under "well-watered" conditions is useful in two ways: |
| 1. Maximizing Yields -- UC research work has indicated that maximum crop yields are attained by providing 60% to 80% of what would be the "well-watered" use of a grapevine. |
| 2. Regulated Deficit Irrigation -- RDI is used in winegrape production to minimize canopy development and to modify berry growth characteristics. |
| The five input parameters needed to calculate well-water use are given below with descriptions: |
| 1) Weather Station Data -- Average (normal) temperatures are used to determine the accumulation of degree-days starting on March 15 and the Reference Evapotranspiration (ETo) at a specific CIMIS weather station. |
| 2) Trellis Type -- The amount of water used by a grapevine at different times during the growing season is a direct function of the "percent of shaded area" (i.e. vine canopies that intercept more sunlight use more water). This calculator uses the Trellis Type to select a specific Crop Curve. The crop curve for the Trellis Type is based on the following trellis systems: |
| California Sprawl (Bilateral Cordon with one cross arm) |
| California Sprawl (Head Trained/cane pruned with or without cross arm) |
| Lyre (or Wye) |
| Quad Cordon (with one cross arm at cordons) |
| Quad Cordon (with cross arm at cordons & cross arm above) |
| VSC (Vertically Separated Canopy) - Scott Henry |
| VSP (Vertical Shoot Positioning) |
| 3) Cross Arm Width -- The width of the trellis cross arm (use zero inches if you have no cross arm or use the widest of cross arms if there are two). This will be used to adjust the Kc value for the cross arm width used during research to the users cross arm width. |
| 4) Row Spacing -- Grapevines planted with closer spacing intercept more sunshine, therefore have a higher water use. |
| 5) Vine Spacing -- In-row vine spacing is used to convert the "inches" of water use to gallons/vine/week. |
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