SmartIrrigation Avocado was developed by the University of Florida and operates on iOS and Android platforms. The app determines an evapotranspiration (ET)-based irrigation schedule using crop evapotranspiration (ETc), irrigation systems characteristics, soil characteristics, and root depth. As shown in Equation 1, ETc is calculated from crop coefficients (Kc; Table 1) and reference evapotranspiration (ETo) data, with the ETo data being determined by using the FAO 56 Penman-Monteith method (Allen et al. 1998):

ETc = KcETo (Equation 1)

Weather data from the Florida Automated Weather Network (FAWN) are automatically downloaded from a station in the network close to the field locations or from a station assigned by the user.

The SmartIrrigation Avocado app generates a 15-day irrigation schedule based on the previous five days of ETc calculations. This schedule is updated any time there is a 50% or greater change in the average ETo for the previous five days.

Table 1.Kc values to compute the ETc values

Growth Stage

Description

Kc

Dormancy Occurs during fall (Nov./Dec.) when temperatures and water demand are generally low.

0.6

Flower bud development Generally Dec. through Feb. depending upon cultivar; low demand for water.

0.8

Flowering and fruit set Occurs during mid- to late winter. Trees typically drop their leaves during this period, although flowering panicles and set fruit require some water.

0.7

Fruit growth Occurs over a 5- to 15-month period depending upon cultivar; high demand for water.

1.0

After harvest Demand for water is reduced during this time.

0.7

Source: Crane (personal communication)