Fruit may also shrivel under conditions of water stress. Growers should have an adequate and dependable supply of good quality water throughout the growing season. Several factors need to be considered when scheduling irrigations. The rate at which soil moisture is removed by the plant depends on the air temperature, amount of solar radiation, humidity, wind speed, plant age, stage of plant development, etc. Water will also be lost from the soil surface by evaporation, and cover crops also use available soil moisture.
Soils differ in water holding capacity.
The following example shows how to determine the water holding capacity of the rooting volume, assuming that blueberries are planted on a sandy loam. The total water available in the rooting volume should not drop below 35 to 50 percent of the total water holding capacity. This assures easy access to water by roots and prevention of drought stress. Continuing the example above, the total amount of water available should not fall below 1 inch, half of the 2-inch total water holding capacity. A blueberry plant growing vigorously in summer can evapotranspire up to 0.25 inches per day.