Challenge 

Most vegetable, berry, citrus and olive production in WA occurs on sandy soils which have a poor capacity to retain water and nutrients. Typically, over 60 per cent of irrigation water and fertiliser applied to vegetable properties on the sandy souls of the Swan Coastal Plain of Western Australia is leached past the rootzone. Nitrogen fertiliser, a significant cost for horticultural producers, is often lost through leaching and runoff.  When this occurs, nitrogen fertiliser can contribute to eutrophication in waterways and wetlands, and coral reef degradation. Water restrictions are also making production challenging for WA growers. For example, in the Wanneroo area, water allocations are being reduced by 10 per cent in 2028, and further reductions are expected in other groundwater areas. Growers must improve water efficiency or be forced to reduce their planting area to adapt.  

Response  

This project is investigating the use of geomembranes —synthetic, impermeable liners installed beneath the rootzone of crops— to collect leachate and divert it into dams for reuse. Key aspects under investigation include:  

• The design and construction of the production system.
• How many times can water be recycled before being dumped due to elevated salinity.
• Soil health and pathogen control.
• Return on investment for growers.  

A demonstration site will be established on a commercial property to extend the approach to industry and demonstrate commercial scale implementation. Growers will also be informed of research findings through field days, presentations, videos, and other communications materials.  

Benefit  

• Increased profitability: Recycling nitrogen and water will significantly reduce input costs, potentially cutting irrigation water and fertiliser use by over 50 per cent.
• Environmental protection: The system has potential to mitigate nitrogen runoff, reducing eutrophication of waterways and damage to ecosystems. This will enable horticulture to be practiced in environmentally sensitive areas like the Peel Harvey catchment, where unallocated groundwater resources exist. 
• Grower resilience: Adopting the system will enable growers to adapt to reductions in water allocations and better cope with drought conditions, supporting sustainability in the face of climate change.