The 2009 ASHS Annual Conference

The study was designed to (a) help small-scale growers understand water stress management, (b) assess water stress effect on tomato fresh fruit quality, and (c) document water savings strategies.  It includes five incremental irrigation treatments, based on CIMIS (California Irrigation Management Information System) evapotranspiration (ET) data: 0, 25, 50, 75, and 100% ET. 

Tomato variety ” Early Girl” was used since it has proven adaptable to water deficient treatments.  Eight week-old plants were transplanted to the field and watered for 10 days before drip irrigation regimes were imposed.  The 100% ET treatment received all the water needed to satisfy its ET needs, while the other treatments received decreasing increments of water. .

Each plot consisted of 40-foot long bed spaced at five feet.  All treatments were watered at the same time.

Data collection included fruit yield and yield components, sensory evaluation, and chemical analyses.

Yield data revealed that “Early Girl” showed remarkable elasticity to water stress.  Treatments biological yields did not significantly vary.  Marketable yield fell by 15-20% in the driest treatments.  However, 100 and 75% ET treatments netted more of extra-large fruit, 21-23% respectively relative to their marketable yield.  At the same time, 0 and 50% ET resulted in more medium and small fruit.  Similarly, combined blossom-end-rot (BER) and sunburned (SB) fruit incidence were higher in the drier treatments (25-29%%) than in the well-irrigated plots (12-13%).   The two driest treatments also resulted in the highest percentages of rejects due to insect and disease presence.

Ripened fruit color was good (hue values of 37.4 to 39.3) for all treatments with no significant differences.  Skin toughness showed very little difference due to water stress.

Taste panels generally favored fruit produced in the stressed plots over those receiving 100 and 75% ET.  Some reported some skin toughness especially in well-watered fruit.  In general, stressed plots produced fruit that tasters favored in terms of flavor, aroma, appearance, texture, and overall fruit quality. 

Laboratory analyses confirmed most of these sensory preferences.  Sugar glucose and fructose, concentrations were highest in the 0 and 25% ET fruits (48 and 47 mg/L, respectively) and significantly decreased as water input increased.   The dry weight and soluble solids showed similar trends.  Lycopene content increased from 5mg/g FW at 100% ET to 7µg/g at 0% ET.   Fruit Ascorbic acid content, pH, and titratable acidity were not significantly different among treatments