Irrigation looks beyond the latest equipment

Current commercial irrigation technologies may not be enough to help irrigated agriculture perform to its potential, particularly in times of water scarcity.

Research being undertaken by Richard Stirzaker at CSIRO and funded by the National Program for Sustainable Irrigation is combining different lines of information in an attempt to get a clearer picture of how well irrigation is being managed. These include knowledge of the irrigator based on experience, actual irrigation as a fraction of maximum potential crop water use, soil water potential monitoring, depth of wetting front penetration and electrical conductivity at the wetting front.

The National Program for Sustainable Irrigation project is titled Adaptive Learning Through Five Strands of Root-zone Knowledge. As the title suggests, the aim is to combine grower experience with simple monitoring in a “learning by doing” approach.

Value of the multi-strand approach has been shown in field trials where one line of information indicating a crop is under-irrigated can be contradicted by another line of information, prompting managers to reframe questions and deepen their understanding. Management can be further refined by strands of knowledge which show when loss of water beyond the root-zone is likely to occur or when nitrate leaching should be monitored. In essence, a new way to learn about what matters in irrigation is being built.

An example Richard Stirzaker offers is the overwhelming focus on water in measurement systems, when inclusion of solutes in the pool of knowledge gives a greater insight into irrigation performance while being a tracer that provides a bigger picture view of the effects of irrigation.

“There are also sustainability reasons for an interest in salt because this is a bigger threat to agricultural production than lack of water,” he said. “Similarly, nitrogen, being the biggest greenhouse contribution from agriculture, deserves much more attention.”

This illustration highlights the need for ecology to be considered alongside engineering in the design and management of irrigation systems. The human factor comes into the picture more strongly too, with producers able to combine their practical experiences with monitored data.

A development in progress arising from work to date is a data collection and delivery system that can accommodate the five strands of knowledge. It is being developed and tested in laboratory and field conditions and includes automatic salt measurement by a new sensor fitted inside the reservoir at the base of a Full Stop wetting front detector.

Measurement Engineering Australia (MEA) took on the task of manufacturing, programming and testing sensor prototypes. A contribution to the costs of developing the tooling for manufacture was made by the Cooperative Research Centre for Irrigation Futures. The final product, yet to be commercialised, includes a four-electrode temperature compensating conductivity sensor.

By monitoring salinity at the wetting front, the “addition knowledge” picture described by Richard Stirzaker appears. The measurement of salts by electrical conductivity (EC) showed low levels at the end of winter at a Riverland vineyard field site, with levels rising during the irrigation season and spiking with each irrigation event. There was a clear correlation of rising EC levels with canopy development and in increase in transpiration. Effects of rainfall were also clear. The first two falls of rain in the irrigation season made little difference to EC levels but a third front of rain caused a significant lowering of levels.

Engineering director and co-founder of MEA, Andrew Skinner, believes accuracy and simplicity of the device will be welcomed by researchers as well as growers seeking data. Options until this time have included complex and expensive devices mainly used for research purposes, and sampling methods where applied vacuums and evaporation could cause errors. All tools for measuring solutes, however, are currently under examination by CSIRO.

“The technology acts as a window below ground to see something that is important to the crop as well as the environment, namely the movement and concentrations of salt fluxes,” Andrew Skinner said. “This is the first practical soil salinity monitoring tool to be developed for producers of irrigated crops.”

With parties like MEA and a number of scientists and producers involved across several experimental sites in different regions, new approaches to irrigation management are emerging.

Citation

Land & Water Australia. 2010. Irrigation looks beyond the latest equipment . [Online] (Updated March 24th, 2010)
Available at: http://lwa.gov.au/node/3722 [Accessed Wednesday 29th of February 2012 08:16:27 PM ].