Australia…. summers are hot and long. This can affect the water absorbency of our soils.
For many of us in the West, our soils are sandy – gutless, hydrophobic and nutrient-less. It is worth noting that many plants grow well in this type of soil, with one of the main advantages of sand over clay being that it has good drainage. However, sandy soils can often become water repellent over time, or hydrophobic. It results in uneven wetting of the soil profile, leading to patchy and uneven plant emergence and reduced productivity. Water repellent soils occupy more than 5 million hectares of western and southern Australia (Roper, 2004)1.
Nature has worked up a waxy coating around the particles of sand which repels water instead of absorbing it to provide moisture for plant growth. The problem can be worsened by prolonged periods without rain or water – often the case in our region. The good news is hydrophobic soils can be remedied; what we need to do is wash that coating away.
Nature is amazing… Some trees fix this on their own; clever things. Rain drips its way down the trunk of the tree, collecting chemicals as it goes, creating a foam at the base of the tree that acts the same as a soil wetter you’d buy from your local nursery. It’s quite amazing to watch.
Soil that repels water will always end up with streams or tunnels through it, sometimes washing away our good topsoil and never getting to the entire root system of our precious plants.
Managing water repellence
Soil amelioration activities such as adding compost, clay, and mulch will greatly improve soil health, which will become a haven for the hard working bacteria responsible for bringing life to overworked or barren ground.
It goes without saying that Perth’s nutrient-depleted soils need soil conditioning. Usually, a ratio of between 30 and 50% soil conditioner to 70-50% soil is recommended; the amount varies depending on the soil’s quality. Soil improver comes in bags or bulk quantities. Manure is also often added to the planting hole.
Clay, because of its density, retains moisture well. It also tends to be more nutrient-rich than other soil types. This is because the particles in clay soil are negatively charged, which means they attract and hold positively charged particles, such as calcium, potassium, and magnesium.
Using organic mulch will also help to retain moisture as it breaks down into the soil.
Soil Wetting Agents
The simplest way to improve water take-up by hydrophobic soils and help it spread more evenly throughout is to use a soil wetter. Soil wetting agents reduce the effects of repellence by lowering the water’s surface tension, which improves infiltration. They have combinations of chemicals that can help water enter and be retained in water repellent soils.
There are economics involved, but it is clear that the benefits far outweigh the overall outlay. There are affordable options of adding a wetting agent along with your fertiliser treatment or product to get better plant quality even during stressful conditions.
It is proposed that WA water licence holders reduce their water usage by 10% in coming years, and this is certainly one effective way to contribute to this target. Soil wetters are also advisable for school gardens and turf where the pressure to save water is constant. The City of Geraldton uses Richgro’s professional strength wetting agent Ezi-Wet as part of their regular ongoing maintenance.
Wetting agents have also become an integral ‘tool’ in turf management. During times of water restrictions, or extended periods of water stress to turf, playing fields’ profiles can also become hydrophobic. Wetting agents will significantly increase the water-holding capacity of soils, therefore, reducing the quantity and frequency of irrigation – a critical cost component of turf management.
Water….. It’s Life!!
1.Roper MM (2004) The isolation and characterisation of bacteria with the potential to degrade waxes that cause waterrepellency in sandy soils. Australia Journal of Soil Research 42: 427-433.