Soil Moisture Management

Author: Stefan Palm   Date Posted: 21 January 2021 

Soil moisture management is critical to health of any lawn. So what's the difference between a wetting agent and a water retention agent and how can you utilise them both to ensure a healthy lawn with less water?

Last weekend on ABC talkback gardening, we talked about moisture management, with particular reference to both wetting agents and water retention agents. As I’ve talked about before (a lot!), most soils in South Australia don’t absorb water evenly. Some don’t absorb it at all leading to wasted water and patchy lawns, especially during Summer.  The best way to make the most out of all the water that is applied to your lawn (both rain and irrigation) is with the use of wetting agents and water retention agents.

Both wetting agents and water retention agents do amazing things for lawns so let’s talk about both of them individually.

Wetting Agents:

Liquid wetting agents are used to treat lawns that are non-wetting or repel water or simply as a treatment to ensure the even penetration of water. They break the surface tension of water and help to dissolve waxy and oily residues in the soil. This allows water to freely and evenly soak in without wastage or runoff. Wetting agents are critical to lawn health, especially during Summer.

Wetting agents:

  • Instantly overcome non wetting or water repellent soils
  • Allow water to penetrate deep into the soil
  • Ensure that water penetrates evenly across the entire surface

Apply a hose on wetting agent such as Paul Munns Betta Wet in November and January every year. Available in a 2L hose on pack which covers 100 square metres

Water Retention Agents:

While most people have heard about wetting agents, water retention agents are something you may not be aware of. As the name suggests, these products have the capacity to store water in the soil meaning you won't need to apply water as  much or as often. Water retention agents work in lawns in a similar way to how water storage crystals work in gardens, the difference being that water retention agents are applied as a liquid (either sprayed on or via a hose on applicator) and then cure in the soil where they absorb and hold onto water. 

If your soil is not water repellent, you can simply use a water retention agent as part of your management program in an effort to conserve water, especially in situations where water drains quickly from the soil.   If you do have a water repellent soil, you’ll have to use a wetting agent before you use a water retention agent, otherwise the water retention agent will not be able to evenly filter down into the soil profile.

Water retention agents:

  • Can reduce irrigation requirements by half
  • Can increase moisture content by up to 5x in the root zone
  • Last for up to 6 months

For best results, apply a water retention agent such as SST Bi-Agra once per year in November.  Available in a 2L hose on pack which covers 150 square metres. Remember, if you soil is water repellent, you’ll have to apply a wetting agent first. Once watered in, you can apply Bi-Agra straight away, on the same day.

In a nutshell, wetting agents overcome non-wetting soils and draw water in. Water retention agents keep it there for longer.


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