|Williams, L - UNIVERSITY OF CALIFORNIA|
|Phene, Claude - BCP ELECTRONICS|
|Grimes, D - UNIVERSITY OF CALIFORNIA|
Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2002
Publication Date: March 18, 2003
Citation: Irrig Sci (2003) 22: 11-18. Interpretive Summary: Accurate scheduling of irrigation can reduce water use and increase crop yield and quality. Scheduling irrigation is especially difficult for young crops. Using a weighing lysimeter, a precise method of measuring the water use of a crop, the water requirements of newly planted grapevines was measured for three years. The water use was related to weather factors that affect evaporation (potential evapotransporation, ETo) to develop a crop coefficient for the young grape vines. The vines in the lysimeters used about 300 mm of water the first year, and 400 and 580 mm the second and third years, respectively. The seasonal crop coefficient begins low as the vine begins to leaf out, then increases through the season as the vine grows. With the coefficient and ETo, which is available to growers in most western states, growers can precisely schedule irrigations for their young vines.
Technical Abstract: Water use of Thompson Seedless grapevines during the first three years of vineyard establishment was measured with a large weighing lysimeter near Fresno, California. Two grapevines were planted in a 2 m by 4 m by 2 m deep lysimeter in 1987. The row and vine spacings in the 1.4 ha vineyard surrounding the lysimeter were approximately 3.51 and 2.15 m, respectively. Vines in the lysimeter were furrow irrigated from planting until the first week of September in 1987. They subsequently were irrigated with subsurface drip irrigation whenever they used 2 mm of water, based upon the area of the lysimeter. The trellis system, installed the second year, consisted of a 2.13 m stake, driven into the soil 0.45 m with a 0.6 m cross-arm placed at the top of the stake. Crop coefficients (kc) were calculated using measured water losses from the lysimeter (ETc) and potential evapotranspiration (ETo) obtained from a CIMIS weather station located 2 km from the vineyard. Water use of the vines in 1987 from planting to September was approximately 300 mm, based upon the area allotted per vine surrounding the lysimeter. Water use just subsequent to an irrigation event could exceed ETo (> 6.8 mm per day) for a day. Water use from budbreak until the end of October in 1988 and 1989 was 406 and 584 mm, respectively. The initiation of subsurface drip irrigation on May 23rd in 1988 and April 29th in 1989, doubled ETc measured prior to those dates. The seasonal kc in 1988 increased throughout the season and reached its peak (0.73) in October. The highest kc in 1989 occurred in July. The seasonal and year-to-year variation in the kc was a result of the growth habit of the vines due to training during vineyard establishment. The results provide estimates of ETc and kc for use in scheduling irrigations during vineyard establishment in the San Joaquin Valley of California and elsewhere.