permanent layout was evaluated.
The individual sprinklers were evaluated on the sprinkler test bench of
the ARC-Institute for Agricultural
Engineering, and the installed systems were evaluated in-field. The
performance of the Coefficient of
Uniformity (CU), Distribution Uniformity (DU) and the Scheduling
Coefficient (SC) were determined.
The importance of this is that high
values of CU, and DU values in-field
has a direct influence on the potential yield of the crop. In this research it was illustrated that layout,
pressure variation, droplet size and
maintenance of sprinkler systems
have a significant impact on the
irrigation system’s performance.
Measuring of water
In a WRC supported project, research work undertaken over the
last 10 years has shown that suitable technologies and devices are
available for the measureme nt of
irrigation water, even in challenging
situations with regards to aspects
such as water quality and installation conditions. Failure of measuring devices or systems can usually
be blamed on incorrect selection,
application, installation or maintenance rather than on the technology itself. Under demanding conditions, it is imperative that the best
technology or device available and
affordable is obtained, to ensure a
sustainable system that will serve
the purpose that the owners of the
system intended it for. The benefits
of a suitable system will pay for
itself within a short period of time
but an unreliable system will only
cause frustration and lead to unnecessary expenses and an additional work load on the water managers of a scheme.
Managing surface- and subsurface drip irrigation systems
Drip irrigation is considered as one
of the most efficient irrigation systems available, but through a WRC
supported research project evidence
was obtained from literature as well
as on-farm and in-field testing that
even this system can also be inefficient, as a result of poor water
quality,
mismanagement
and
maintenance problems. Apart from
the research on the performance of
various types and ages of drippers
and filters under different water
quality and typical farming conditions, guidelines were developed to
make the correct dripper and filter
choice. Through this research excellent guidelines were provided for
proper choice, maintenance schedules and management of filters and
drip irrigation systems. As a follow
up further research resulted in two
manuals on “Technology transfer
on the technical aspects and cost
estimating procedures of surface
and subsurface drip irrigation systems”, one for designers and one
for farmers to manage their sys-
Infiltrometer to size centre pivots
tems.
The water balance approach
In a recently completed WRC research project on irrigation efficiency, the selected approach is that
irrigation efficiency should be assessed by applying a water balance
to a specific situation, rather than
by the calculation of various performance indicators, based on once
off measurements of samples. The
purpose of an irrigation system is to
apply the desired amount of water,
at the correct application rate and
uniformly to the whole field, at the
right time, with the least amount of
non-beneficial water consumption
(losses), and as economically as
possible. When applying water to
crops, it should be considered both
as a scarce and valuable resource
and an agricultural input to be used
optimally. Not all the water that is
abstracted from a source for the
purpose of irrigation, reaches the
intended destination where the
plant can make best use of it – the
root zone. The fraction of the water
abstracted from the source that is
utilised by a planted crop, is called
the beneficial water use component. Optimised irrigation water
supply is therefore aimed at maximising this component and implies
that water must be delivered from
the source to the field both efficiently (with the least volume for
production along the supply sys-
Testing of sprinklers