Remote water quality monitoring – an easier way to watch every drop
By David Hunt, GIA Smart Farming Project Officer
The nursery industry has invested decades of research and development in irrigation Best Management Practice (BMP) to assist nursery managers to maintain water quality and supply. However, there is always room for improvement if we are to help nursery operators embrace more efficient water management, smooth out the water cycle, and increase the industry’s environmental sustainability.
Installing water quality sensors (pH, EC, Redox) in runoff drain
We all know that Australia is the driest continent on earth. However, it seems our attitude to water is related to how much we have at any given time. When water is plentiful, we throw it around like there is an unlimited supply. When it is scarce, we act like this problem is happening for the very first time. New technologies are being implemented to help nurseries smooth out this water cycle roller-coaster.
Greenlife Industry Australia (GIA) as part of the Smart Farming Partnerships project funded under the National Landcare program and Hort Innovation, is installing new remote monitoring technologies that help nursery managers get a real-time overview of their water storage and quality. This project aims to maximise the industry benefit from environmental monitoring to support real-time decision making. The project firmly targets the parameters within EcoHort, the industry’s environmental BMP program, and considerable effort is being put in to develop remote monitoring and digitisation options.
The EcoHort guidelines have some very effective irrigation monitoring criteria and provide checklists for irrigation managers to ensure the irrigation system and water quality meets industry BMP standards. This includes applying irrigation with a mean application rate (MAR) of less than 25mm/hr, a Coefficient of Uniformity (CU) of above 85%, and a Scheduling Coefficient (SC) less than 1.5. In a nutshell, it is about applying water at a rate that the growing media can absorb, having the sprinklers laid out in an appropriate grid pattern to ensure uniformed coverage, and that the system efficiently applies water so not to waste fertiliser inputs by overwatering and flushing nutrients in to drains, dams, or local waterways.
Irrigation line pressure
For example, if we assume that an irrigation system meets the BMP standards, what else can be done to ensure the best growth and plant health outcome? EcoHort provides other vital criteria that can help to meet and surpass BMP requirements. The first of which is irrigation line pressure. If the sprinklers are laid out in an appropriate grid pattern to suit the sprinklers type and model, the sprinkler specification sheet will provide the optimum operating pressure (usually in kPa) that will ensure the sprinklers meet their performance target. Too much or too little pressure will change the sprinklers’ application efficiency and negate much of what was gained by installing a system to industry best practice. Installing pressure transducers in the irrigation line will monitor line pressure to allow the pump operation to be adjusted to sprinkler requirements, increasing pump and application efficiency.
A second criteria often overlooked or misunderstood is the ‘Leaching Fraction’. EcoHort guidelines suggest a target of about 12% as an ideal amount. In theory, irrigation is applied at a rate to replace water lost to evapotranspiration. Therefore, irrigation will need to be applied so 12% of the irrigation water is leached from the container. This keeps fertiliser in the root zone where it is needed for maximum growth and allows for a modest flush of salts, which reduces any potential environmental impact from excessive leaching of nutrients.
The GIA Smart Farming project is implementing a system to remotely monitor basic water parameters such as pH, electrical conductivity (EC), nitrate and phosphate, as well as irrigation line pressure and the leachate volume for each irrigation event. This data is displayed and recorded on an ‘operations dashboard’ to show the historical fluctuations in irrigation and runoff water quality while providing a real-time alert mechanism if any parameter drifts outside of the EcoHort guidelines.
Example of the operations dashboard showing wastewater parameters