Photo 1: Dripper and soil monitoring with GPRS data transmitting
and actual evaporative demand.
When this ratio drops, it indicates
that soil water supply becomes limiting and that water stress is occurring. The deficit at this point in
time is the maximum depletion level, while the ratio before this drop
occurs is the crop factor.
ble, if probe data from a field is not
collected in a given period or when
the deficit on a field exceeds a certain critical level. These warnings
can be displayed on the computer
screen or smart phone and can be
sent by SMS to the person responsible for attending to the situation.
All calculations are automated and
allow irrigation managers to easily
check the results in easy to access
graphs and tables (see Figure 2)
either on a computer or on a smart
phone.
Water saving is due to the following factors:
The system enables the user to
determine the maximum safe
depletion level. This enables the
maximizing of irrigation
amounts and the minimizing of
evaporation losses. The longer
irrigation intervals help to create
soil conditions with more oxygen for root and microbial life.
The program automatically checks
all data and warns users if something needs attention. For instance
if a probe battery needs to be replaced, if any probe sensor is unsta-
Better decisions due to accurate
refinement of parameters such as
crop factors, field water capacities
and application rates lead to more
accurate decisions. For example:
Both water use and evaporative
demand are measured and the
crop factor is calculated automatically as the water used divided by
the evaporative demand.
Quicker decision making by applying a standardized process and
following the recommendations.
More accurate execution of the
decisions due the results that are
displayed in graphs.
It is important to state that the
purpose of irrigation scheduling is
not confined to saving water only,
but is to optimize water use. In
most cases crops are over irrigated for most of the time and under
irrigated for shorter periods from
time to time. The scheduling system can therefore, in some cases,
lead to increases in water use efficiencies without any savings in
water use.
Proven saving of water with precision irrigation
The Irricheck system has been in use
since 2008 at the Karsten Farms, one
of the largest irrigation farming enterprises in South Africa, They are
growing mainly table grapes for export on 1082 ha on 9 farms on the
banks of the Lower Orange River be-
Figure 2: Graph with water content per soil layer