Irrigation scheduling and Smart technologies – Is your irrigation system ready?

By David Hunt, GIA Smart Farming Project Officer
 

For many years the nursery industry has promoted the benefits of installing an irrigation system to industry best practice as a way of improving water use efficiency and reducing a business' operating costs. However, as we move into a new era of smart technologies and automated production systems, having a highly efficient irrigation system is proving to be more important than ever before.

A good irrigation system is more than just a method of applying water to plants. An efficient well designed irrigation system will influence nutrient availability and leaching, root development, plant health and marketability, disease and pest susceptibility, as well as water, energy, and labour costs. An irrigation system that can be adjusted to suit the life stage and water requirements of the plants is just as important as having customers to buy the plants.

An efficient irrigation system is one that matches the irrigation application rate to the water infiltration rate of the growing media and the plants’ water requirements. Combining an efficient irrigation system with new smart technologies can help to provide a good balance between resource use and producing a healthy marketable plant. Installing various smart technologies such as integrated weather stations, soil moisture sensors, weight scales, plant sensors, flow meters or pressure transducers can help to manage the irrigation system and other associated production systems to reduce water, energy and fertiliser usage. These sensors can also act as an early warning mechanism if some part of the irrigation system fails (Hunt 2008).

As part of the Smart Farming Partnerships project funded under the National Landcare program, Greenlife Industry Australia (GIA) and Hort Innovation, a number of smart irrigation sensors have been installed at key locations around the project’s Smart production nursery.

Soil moisture sensors and weight scales can show when container moisture is below acceptable levels or how long to the next irrigation. Plant sensors can show when the plants are in stress. Flow meters or pressure sensors can help to identify the system is operating to specifications or if there is a pipe blowout, and leachate sensors can identify the right amount of water has been leached from the containers. Once the sensors are calibrated and connected to the irrigation controller, they will automate irrigation by starting or pausing irrigation according to the plants’ water requirements or alert the nursery manager if the system fails to operate as programmed.

However, smart technologies cannot correct a poorly designed or installed irrigation system. Substantial amounts of money could be spent on purchasing smart technologies and calibrating the system, but unless the uniformity and efficiency of the irrigation system is first addressed, the addition of smart technologies will not improve the application efficiency of a poorly designed irrigation system. That is, smart technologies installed into a production nursery may improve irrigation scheduling practices but will not fix the issues of uneven water application, incorrect operating pressures, or a poor water distribution system.
 

To achieve the most benefit from installing smart irrigation technologies, the irrigation system itself should be assessed and upgraded to ensure it meets the nursery industry Best Management Practice for an irrigation system. The irrigation system should have a mean application rate (MAR) equal to or less than the absorption rate of the growing media (or less than 20 mm/h), apply water evenly over the whole area with a coefficient of uniformity (CU) of 85% or higher, and have a scheduling coefficient (SC) between 1 and 1.5 (Rolfe, et. al. 2000).

There are several components of an irrigation system that influences the application efficiency which should be assessed if the system does not meet any of the efficiency measurements. These include:

• Sprinkler type, jets, plates and trajectory e.g., spinner or rotating stream
• Sprinkler spacing – correct spacing to suit sprinkler type
• Height above crop – appropriate for plant growth, and sprinkler trajectory and spacing
• Operating pressure – meets sprinkler specifications
• Flow rate – meets sprinkler specification
• Energy efficient irrigation pump – provides the correct operating pressure and flow rate while using the least energy possible. Incorrect operating pressure and flow rates will increase energy usage.

All these components should be considered when assessing the efficiency of an irrigation system as each component will affect how the system works. However, if the irrigation system meets the operating and efficiency parameters then incorporating smart control technologies and sensors has the potential to increase productivity, save resources, and reduce plant stress by more precisely matching the irrigation to the plants’ water requirements. So, if you are considering installing smart technologies or sensors, it is a good idea to check your irrigation system is ready and able to provide all the benefits of smart technologies.

References

Hunt, D.S., 2008. Increasing Adoption of Irrigation and Water Recycling Technologies in Australian Nurseries: FINAL Report for Project PA 57134 http://era.daf.qld.gov.au/id/eprint/2502/1/PA57134_Increasing_Adoption_of_Irrigation_and_Water_Recycling_Technologies_in_Australian_Nurseries.pdf
Rolfe, C., Yiasumi, W., & Keskula, E., 2000. Managing water in plant nurseries. 2^nd Ed. ISBN: 0734711808. NSW Agriculture. (3^rd Edition available)

Further Readings

Rolfe, C., 2006., ‘Scheduling irrigation to maximise efficiency’, Greenlife Industry Australia, Nursery Paper, August 2006 Issue no.8, viewed 23 August 2021. https://www.greenlifeindustry.com.au/static/uploads/files/ngia-np-2006-08-august-wfpuyrjtefqu.pdf
Irrigation Toolbox Calculators: https://nurseryproductionfms.com.au/irrigation-toolbox-calculators/