Agriculture Reference
In-Depth Information
Geospatial
Maps
Gps
Chemicals
Fertilizers
Pesticides
Water deficit
determination
Calendar-based
Evapotranspiration
Soil sensing
Plant sensing
Irrigation controller
Programmable device
Analog interface
Analog-to-digital converter
Communication
Irrigation execution
Solenoid valves
Pressure gauges
Flow meters
Clock
Water source
Pressure
Filters
Booster pump
Electric/generator
Fuel (gas, diesel)
FIGURE 11.1
Schematic of an irrigation control system with separate modules and functions.
is an electronic device capable of storing and executing irrigation scheduling pro-
grams written and managed by human operators to determine if, when, and how
much to irrigate following a number of decision-making steps:
r The irst step is to assess water demand or water deicit determinations
using either a calendar-based soil water balance assessment, a meteorologi-
cally based evapotranspiration estimation, or a direct measurement of soil
or plant water status using
in situ
or remotely located sensors. Direct con-
tinuous communication between these sensors and the irrigation controller
is essential. This can be achieved by directly connecting the sensor outputs
to the analog interface panel for wired systems, or through wireless trans-
mitters/receivers (Kranz et al. 2010).
r If an irrigation is required, the second step is to check water source avail-
ability, which is determined by water pressure in the supply pipe or to initi-
ate an irrigation event through a pressurized system (may include actuation
of an existing well pump or of a booster pump used in conjunction with
water storage, and the pumps may be operated electrically or fossil fueled).
r If an irrigation command is executed, the third step is that a set of con-
trol and monitoring devices are also deployed to complete the irrigation.
Latching solenoid valves are commonly used to turn water flow on or off
with the amount monitored by flow meters or timers using an internal clock
in the controller. In situations where site-specific irrigation (SSI) is per-
formed, such as in center-pivot or linear move systems, geospatial data
will be needed for the controller. Fertigation or chemigation are also com-
monly used in the pressurized irrigation systems with or without system
automation.
