Strawberry Establishment with Drip or Sprinkler Irrigation

Strawberry, a major crop grown in Ventura County, California, has an annual value of $394 million.  Each September, 1.2 m-wide raised beds are constructed with two drip irrigation lines placed 5-10 cm deep and covered with polyethylene mulch.  Narrow holes are cut into the mulch and by October, bare-root plants from high elevation nurseries are planted such that each drip line waters two rows of plants, one row on either side of the line.  For the first 5-8 weeks after planting, however, overhead sprinkler irrigation in daily amounts ranging from 50-60 mm is used instead of drip to rapidly hydrate plants, aid adventitious root development, and leach salts from the root zone.  In a large-scale field study conducted at Camarillo, CA in 2009, we compared strawberry establishment using standard overhead sprinkler irrigation to either reduced sprinkler irrigation or drip-only irrigation with two different placements of four drip lines. Water use, electrical conductivity of soil in planting holes at 5 cm depth (EC), disease incidence, and strawberry performance were measured during the 8-week plant establishment period.  Water use was reduced 34% in drip-only treatments and 20% in the reduced sprinkler irrigation treatment compared to standard sprinkler irrigation.  Soil pore EC was generally greater in drip only treatments than in sprinkler irrigation treatments, ranging from 3.4 to 7.9 dS/m.  In drip-only plots, placement of four drip lines on the bed surface and in planting rows reduced EC of soil 10-40%.  Strawberry mortality was 70% greater in plots where drip tape was buried 5-10 cm deep compared to standard sprinkler, but was less than 2% in all treatments, a level acceptable for commercial production.  Incidence of leaf spot and leaf blotch on strawberry leaves was 75% less in drip and reduced sprinkler treatments compared to standard sprinkler.  Strawberry plants were also 13-18% smaller under standard irrigation compared to other treatments, but more uniform in size.  Dry biomass of new leaves was similar among treatments, but new root biomass in reduced sprinkler and surface drip treatment was 26% and 51% greater, respectively, than with either standard sprinkler or buried drip irrigation.  In drip-only systems, less root biomass was observed in central rows where soil EC was greater.  Early fruit production was similar among treatments. These results suggest that reduced irrigation and precise water placement are adequate for strawberry establishment, provide substantial savings of water, and minimize runoff, a major benefit to the environment.