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Unformatted text preview: VEN 2 IRRIGATION OF GRAPEVINES IN CALIFORNIA Dr. Larry E. Williams Department of Viticulture and Enology INTRODUCTION The Coachella Valley has a desert climate characterized by extremely hot summers (maximum temperatures of 50 o C are not uncommon) and mild winters. Budbreak will occur in mid-January when vines are sprayed with hydrogen cyanamide, and harvest concluded by late May – early June. Fortunately, the extremely high summer temperatures occur in July and August. Rainfall is usually less than 50 mm (there are 25.4 mm per inch) per year. The soils are sandy with low water and nutrient holding capacities. Rooting depth in these soils is limited because they are highly stratified. The evaporative demand (reference ET [ET o ]) in the Coachella Valley from mid-January to the end of harvest can range from 650 to 800 mm. Yearlong ET o can be 2000 mm. The maximum ET o value will approach 8.5 mm per day close to harvest. The San Joaquin Valley is a semi-arid region with hot summers (maximum temperatures approximately 44 o C) and cool winters. Grapevines and deciduous fruit trees will generally accumulate enough chilling units each winter so as not to affect budbreak. Budbreak of grapevines will occur early to mid-March and harvest (depending upon grape type) will occur from the end of July to September. Rainfall is a function of location within the valley, more to the north and less to the south. For example, rainfall in Stockton (at the northern end of the valley) may approach 400 mm per year. Rainfall in the central San Joaquin Valley (Fresno) averages 250 mm per year while that in Bakersfield (southern end of the valley) is approximately 180 mm. The major portion of the rainfall will occur during the winter months. The majority of grapevines are grown in the eastern portion of the San Joaquin Valley where the soils are mostly sandy loams, although there are small areas that can be very sandy. Soils in the western portion of the San Joaquin Valley are heavier, clay loam type soils. The rooting depth of the eastern San Joaquin Valley can be limited by clay-pans. The soil water and nutrient holding capacities of these soils are moderate to good. There can water infiltration problems on some of the soils. Reference ET from the time of budbreak to the end of October will range from 1000 to 1250 mm in the San Joaquin Valley (Figure 1). Daily maximum ET o may approach 7 mm. The coastal, wine grape production areas of California are characterized by warm days and cool nights although high temperatures (40 to 47 o C; 104 to 116 o F) may occur for a few days each growing season depending upon location. Some areas may have fog lasting late into the morning. Rainfall is greater in coastal valleys located further north and diminishes as one travels south. For example, rainfall in the Napa and Sonoma Valleys will range from 500 to 1000 mm (20 to 39 inches) per year while the Salinas Valley averages only 250 mm (10 inches) per year. Reference ET between budbreak and 1 harvest will range from 800 to 1000 mm (31 to 39 inches) in the coastal valleys (Figure...
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This note was uploaded on 09/29/2010 for the course VEN 81437 taught by Professor Larrywilliams during the Fall '10 term at UC Davis.
- Fall '10