TECH CORNER
Using microirrigation to
By
S
One way of conserving water during strawberry plant establishment and freeze protection is the use of micro/ low-volume sprinklers.
trawberry (Fragaria × ananassa Duch.) is a small berry fruit from the Rosaceae family that is well appreciated and consumed worldwide. In the
U.S., strawberries are primarily grown in California and Florida, which account for 91% and 8% of production, respectively. Although Florida has the smaller market share, strawberry production in Florida occurs during the off-season for California. The Florida growing season starts in late September to mid-October to supply fresh strawberries from November to March, when the price is higher than during the rest of the year. In 2022, strawberries were planted on 10,600 acres in Florida, resulting in a production value of $511 million.
Water use in strawberry production in Florida is unique due to its heavy reliance on both sprinkler and drip irrigation systems. Typically, commercial strawberries are planted on raised beds covered with black plastic mulch, with plants in twin rows in a staggered fashion. The plastic mulch serves as a tarp for soil fumigation to control soil-borne pathogens and weeds, and as mulch for conserving soil moisture, warming the soil during the cooler months and keeping the berries clean. The drip tape installed in the center of the beds provides water and fertilizer during the growing season, whereas sprinkler irrigation is used at the beginning of strawberry growing season for bare-root transplant establishment and later in the season for freeze protection. Typically, impact sprinklers are used with fixed square spacing to supply water during both phases.
Although availability of strawberry plug transplants has increased, bare-root strawberry transplants still predominate because of the higher cost of plug transplants. The bare- root transplants have impaired root systems, which make them vulnerable to heat stress during plant establishment, as they are unable to uptake water from the soil efficiently and withstand the high temperatures associated with black plastic mulch (see fig. 1). Consequently, an overhead sprinkler irrigation system is required to maintain a cooler microclimate around the transplant crowns to foster the growth of new roots and avoid the desiccation of the plants (see fig. 2).
Figure 2. Formation of ice over strawberry fruit and leaves during a frost/freeze protection irrigation event.
Overhead sprinkler irrigation is not only used during transplant establishment but also later in the growing season during winter to protect flowers and fruits from cold injury when there is a potential drop in air temperature to freezing and near freezing. Typically, growers turn on their sprinkler systems for cold protection when the temperature reaches 34 degrees and keep them on during the cold event generally until the sun melts the ice.
Figure 1. Planting strawberry bare-root transplants into raised beds covered with black plastic mulch.
30 Irrigation TODAY | Winter 2024
Both management practices use significant amounts of water. For example, the establishment phase for bare-root transplant can last 10-14 days with water applied for eight to 10 hours a day to lower the plastic mulch temperature to promote establishment and early growth. This accounts for one-third (~ 374-534 hundred thousand gallons/acre) of the total water use over the growing season, 97% of which flows off the plastic mulched beds. In Florida, between late September to mid-October this water use accounts for 14.7 million cubic meters of water, which not only lowers the aquifer levels but also constrains water availability for metropolitan areas in west-central Florida, which is the major strawberry growing area in Florida.
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