Nutrient Management Research Database

The effect on crop yield of drip-irrigation frequencies of two irrigations per day (2/d), one
irrigation per day (1/d), two irrigations per week (2/week), and one irrigation per week (1/week) was investigated for lettuce (Lactuca sativa), pepper (Capsicum annuum),
and onion (Allium cepa) grown on sandy loam and processing tomato (Lycopersicon esculentum) grown on silt loam during experiments conducted
during 1994 to 1997. All treatments of a particular crop received the same amount of irrigation water per week. Results showed that the 1/week frequency should be
avoided for the shallow rooted crops in sandy soil. Irrigation frequency had
little effect on yield of tomato, a relatively deep-rooted crop. These results suggest that drip irrigation frequencies of 1/d or 2/week are appropriate in medium to fine texture
soils for the soil and climate of the project site. There was no yield benefit of multiple irrigations per day.

• Crisphead lettuce, processing onion, pepper, and processing tomato were grown from 1994 to 1995 at the University of California Westside Research
  and Extension Center, Five Points, CA.
• Drip irrigation frequency treatments were 2/day, 1/day, 2/week and 1/week.  Each treatment was replicated 6 times in a randomized block experimental design.
• Tomatoes were grown on silt loam; other crops were grown on sandy loam.
• The same amount of water was applied weekly to all treatments of each crop, equaling the calculated crop evapotranspiration.

• Onion: About 30 inches of water was applied to each treatment and maximum marketable yield occurred for the 1/day treatment, while minimum occurred for the 1/week treatment. Differences between other treatments were not statistically significant.
• Lettuce: Cotton defoliant sprayed onto nearby cotton drifted onto the lettuce and damaged the plants in three of the blocks.  Applied water for spring lettuce was 4.5 inches.  There were no significant differences in average lettuce yields between treatments
• Pepper: 15.6 inches of water was applied for each treatment.  The largest yield occurred in the 1/day treatment, and was significantly larger than the 1/week yield.
• Processing tomatoes: Applied water was 16.7 inches. There were no significant differences between treatments in yield, marketable fruit fraction, soluble solids or color.