Article and photos by Felix Reinders
ARC-Institute for Agricultural Engineering
Precision agriculture can be seen as site specific crop management and is a
farming management concept based on observing, measuring and responding to
variability in crops.
C
rop variability typically
has both spatial and temporal components which
makes statistical/
computational treatments quite
involved. This is complimented with
precision irrigation to accurately
manage the irrigation water. Although there are various technologically advanced approaches, precision scheduling is of huge importance. Irricheck’s Irrigation
scheduling water management system, a South African development,
is one of the available options.
The system integrates all the information influencing the crop-soilclimate system, in order to ensure
accurate decisions in all circumstances. The system utilizes the Irricheck Scheduling program, DFM’s
continuous logging probes, a
weather station on the farm, a
weather forecast and regular service by consultants to ensure accurate recommendations.
The Irricheck Irrigation Scheduling system
The heart of the system is the Irricheck Scheduling program. The
computer program automatically
“draws” the weather forecast via
the internet and the actual weather
data from an automatic weather
station (see figure 1). The actual
evaporative demand according to
the actual weather data and the
expected evaporative demand according to the weather forecast are
calculated using the PenmanMonteith equation.
The soil moisture is measured continuously every hour at six depths
by DFM soil moisture probes. The
probe data is collected twice a
week using a portable data logger
or it can be transmitted continuously via GPRS (see photo 1).
The probe measurements (%) are
calibrated to volumetric water con-
tent (mm/m). The program automatically integrates the hourly soil
moisture data, the evaporative demand and the information of the
crop-, soil- and the irrigation system to calculate the required irrigation for each irrigation block for
the coming week.
The system provides lots of information which allows the accurate
refinement of parameters like safe
depletion levels and crop factors.
The program continuously calculates the ratio between water used
Figure1: The Irricheck irrigation scheduling program