Cultivar differences
Strawberry cultivars vary in their vigour, leaf area and fruit production which suggests that different amounts of irrigation and fertiliser are required. For example, Fortuna is recognised as being a smaller, less vigorous plant. Its root system may not explore the soil to the same degree as Camarosa and Festival.
Most growers in Western Australia treat all varieties the same but this may not be the best option, especially for water and fertiliser.
Research at Wanneroo has shown that stand-alone evaporation-based irrigation scheduling does not work well with strawberry crops grown under black plastic mulch, high tunnels or plastic cloches.
Irrigation requirements
Evapotranspiration and the impact of rainfall are altered by plastic mulch and cloches or tunnels.
When rain falls throughout the cooler months, growers often reduce or stop watering in the belief that water falling in the pathways can be accessed by the plants. However, on coarse sandy soils this is not so. Some water does enter the beds during heavy falls (25mm or more) but it is largely below the root zone and serves mostly to leach fertiliser.
Soil moisture monitoring is essential to determine the effectiveness of water applied and the water potential of the soil. Details on using soil moisture sensors to fine-tune irrigation can be found here.
Previous research in Western Australia suggested that replacing 70% of evaporation was adequate to supply plant needs over most of the season. More recent experience indicates that water requirements could be as high as 100% of evaporation for maximum production.
Using soil moisture monitoring equipment to fine-tune irrigation for each particular variety/plant spacing/irrigation configuration and soil type is the best practice.
In Western Australia's sandy soils irrigation should be split into two or three times a day, even four times when daily evaporation gets to around 10mm per day. The aim is to apply small amounts more often (<3mm at a time) to keep fertiliser in the root zone rather than flushing it below the roots.
Many modern soil moisture probes also monitor EC (the concentration of salts in the root zone). That can be useful when levels start to climb, given strawberries are a salt-sensitive crop. If levels rise apply water only, for a day, to leach out the build-up of salts.