in HortScience
Author: T.K. Hartz1
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  • 1 Department of Vegetable Crops, University of California, Davis, CA 95616

Drip irrigation scheduling techniques for fresh market tomato production were compared in three consecutive seasons (1989-1991) in the southern coastal environment of Irvine, California. Three techniques were compared: 1) reference evapotranspiration (ETo, corrected Penman) × programmed crop coefficients (Kc), ranging from 0.2 (crop establishment) to 1.1 (full canopy development); 2) ETo × Kc, based on % canopy cover as estimated by average canopy width per row; and 3) irrigation at 20% available soil moisture depletion (SMD) at 30 cm, with recharge limited to a maximum of 0.8 × cumulative ETo since the previous irrigation. The use of programmed crop coefficients and Kc values based on % canopy cover gave equivalent yields and fruit size distribution in all years; there was no difference in crop response between daily irrigation and irrigation three times a week. Both scheduling techniques maintained soil water content in the top 45 cm near field capacity throughout the growing season. The use of Kc based on % cover required less total irrigation in all seasons, averaging 78% of seasonal ETo vs. 88% with programmed coefficients. Irrigation at 20% SMD required an average of only 66% of seasonal ETo; marketable yield was equivalent with the other scheduling techniques in 1989 and 1991 but showed a modest yield reduction in 1990.