Alternate Furrow Irrigation Reduces Water Applied without Yield Reduction In California Processing Tomatoes.

Irrigation methods that use less water, but produce high yields, contribute to agricultural sustainability. Alternate furrow irrigation (AFI) is based on the partial root zone drying technique, which manages soil moisture to reduce applied water and increase crop water use efficiency (yield/water applied; WUE). Past research has shown promising physiological responses to partial root drying, but strategies for reliable crop management need more attention. AFI consists of selectively watering only every other furrow at each irrigation, while the ‘dry’ furrows receive water at the next irrigation. Furrow irrigation in California is used on ~50% of tomato fields. We hypothesized that, compared to every furrow irrigation (EFI): 1) AFI may reduce vegetative growth and soil canopy cover at the beginning of the season, but this difference may disappear after plant establishment and development of an extensive root system; 2) Plants under AFI may slightly reduce their stomatal conductance because of less water availability in the root zone, but photosynthetic rates may not change; 3) Yields under AFI and EFI may be similar, but total applied water may be reduced, increasing WUE. Two highly-productive processing tomato cultivars in a field study were used to evaluate the effects of AFI on plant morphological and physiological responses, and yields. Total applied water, soil moisture, canopy cover, leaf gas exchange measurements, aboveground biomass, yield and fruit quality were measured. Preliminary results show that stomatal conductance was unexpectedly higher in AFI at ~60 days after transplanting, and otherwise was similar to EFI. The irrigation treatments had similar total aboveground biomass and soil canopy cover. Water applied to AFI was reduced by 25% with no significant differences in yield (fresh weight) or fruit quality. AFI increased WUE by 30%.