Management of hydrophobic soils
Hydrophobic (water-repellent) soils are an issue because the water from rainfall or irrigation does not wet the soil to its full water-holding capacity, which in turn reduces the amount of water available for plants.
Our research compares different treatments to find the most effective solution. This involves measuring the amounts of rainfall and irrigation against soil moisture levels.
Since 1994, Royal Botanic Gardens Melbourne has taken a lead role in implementing management strategies for the efficient use of water.
Protecting the heritage landscape of RBG Melbourne depends on improved understanding of the future trends in available soil water. This knowledge assists us to plan and manage living plant collections and day-to-day decisions regarding plant selection.
Over the last 13 years of record drought, water-repellent or hydrophobic (literally ‘water hating’) soils are one of the emerging issues in the landscape. While 2010 has seen the return of reasonable rainfall to the RBG, the 2010 total has actually only been 10% above Melbourne’s long term average of 649mm It is possible that once the influence of the current unprecedented La Nina (since the 1970’s) departs, that a return to drier conditions may be ‘normal’ again.
Soil water repellency is a problem as water from rainfall or irrigation often runs off the soil surface or moves down through the soil without wetting it properly. This limits the amount of water that a soil can hold for plants to use. It is also a concern that continued global warming and less reliable rainfall may worsen this problem.
RBG Melbourne is completing a research project to discover which treatments work most effectively without causing other environmental issues. A total of 6 sites have been selected for trials across the Gardens. A portable soil moisture sensor is being used to measure soil water at regular times, and catch-cans are being used to measure the amounts of rainfall and irrigation that are applied.
Related documents
Water running off the surface of water-repellent sandy soil
Water-repellent soil under mulch
Section of soil in the Australian Forest Walk showing preferential flow of water downwards. The soil remains dry in between these narrow 'fingers' of moistened soil, which in turn limits the soil water-holding capacity.
Last updated 24 Jan 2011
