The last of a four-year study to investigate the effects of irrigation frequency on Thompson Seedless productivity was concluded in 2001. The irrigation frequency treatments included: a.) The application of water whenever the vines in a weighing lysimeter used 2mm (2.11 gallons) of water, b.) The application of water once a day (the amount being equivalent to the day’s use of water by the lysimeter), c.) The application of water every three days (the amount being equivalent to three days use of water by the lysimeter) and d.) The application of water once a week (the amount being equal to seven days use of water by the lysimeter). In addition to the frequency treatments, water was applied in three different amounts: 60, 80 and 100%of lysimeter vine water use. Lastly, three different trellis treatments were included. The trellis treatments consisted of a single wire, a 0.6 m (2 ft) crossarm and a 1.2 m (4 ft) crossarm. Vine density in the vineyard was 1318 vines per hectare (533 vines per acre).Irrigation of the vines in the lysimeter and the rest of the vineyard commenced on May 29th. Vine water use between budbreak and harvest was 4599 liters (1217 gallons). The water use between budbreak and harvest was equivalent to 609 mm (approximately 24 inches). Applied water between budbreak and harvest was 3915 liters (1035 gallons) or 518 mm (20.4 inches) of water. The amount of water applied to the 60, 80 and 100%of ET irrigation amounts was 58, 76 and 100%of actual vine water use (measured with the weighing lysimeter). There were significant effects of irrigation amounts, frequencies and trellis type on berry weight and soluble solids in 1999 and 2000, but no significant interactions. There were no significant effects of irrigation amounts or frequency on final yield in either 1999 or 2000. The results in those two years at the three irrigation amounts were similar to those obtained in previous studies in this vineyard when irrigations commenced prior to bloom, as done in 1999 and 2000. During the 2001-growing season, irrigations were delayed purposely to see how this could affect the results. There were significant irrigation amount by irrigation frequency effects on berry weight, soluble solids and yields in 2001. The delay in starting irrigations resulted in smaller berries for all treatments compared to data from 2000. In general, vines irrigated at the higher frequencies and/or irrigation amounts at 100%of ETc had the largest berries and highest yields in 2001. These results illustrate that deficit irrigation management practices for Thompson Seedless grapevines can maintain productivity similar to that of fully irrigated vines, if the irrigations are commenced prior to bloom under the conditions of this study.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF2002-10-17 11:10:242017-10-17 11:11:03Effect of Irrigation Frequency on Productivity of Thompson Seedless Grapevines Grown in the San Joaquin Valley Using Drip Irrigation