5 ways to boost your soil

If you want your garden to really flourish, then it’s time to talk dirt!

It's every gardener’s dream to have beautifully rich soil – packed with nutrients and beneficial microbes. Soil that retains moisture easily, yet still drains freely. This kind of soil promotes healthy root systems and vigorous plant growth, with an abundance of flowers and fruit. Unfortunately, most soils are far from perfect and often in desperate need of improvement. Here are five ways you can improve your soil:

 

1. Test your soil pH

When soils are too acidic, or too alkaline, plants can have trouble absorbing certain nutrients. Even though the nutrients are physically sitting in the soil they become ‘locked up’ and plants can suffer from deficiencies. The sweet spot for most plants is a soil that is neutral to slightly acidic (pH6-7). The good news is you can easily test your soil with a pH test kit or probe, available from nurseries. If the soil is too acidic (pH below 6) then apply lime or dolomite, and if it’s too alkaline (pH above 7) apply sulphur. Test the soil again in 3-6 months to see if further applications are needed.​

2. Add missing ingredients

You can improve the structure of your sandy and clay soils by adding special ingredients called ameliorants or amendments. For sandy soils, the addition of bentonite or kaolin clay makes the soil a bit ‘stickier’, which in turn efficiently improves its water- and nutrient-holding capacity. For many clay soils, the addition of gypsum effectively helps to break up the clay and improve the soil's drainage. And lastly, you can increase the mineral levels in all soil types with the addition of slow-release rock dust.

3. Boost the organic matter 

The other magic ingredient for improving any kind of soil is organic matter, most commonly in the form of compost, aged manures and worm castings. These high carbon ingredients add valuable nutrients along with beneficial microbes to improve soil fertility and structure. Be generous when applying for maximum benefits.

4. Grow green manure 

Another way to boost organic matter in your soil is to grow a 'green manure' crop. Nurseries sell green manure seed blends (typically a mix of legumes, brassicas and grasses) which should be thickly sown over the area you want to improve. Let the crop grow to approximately 30cm high, then cut the growth off at ground level. Use a garden fork to turn everything into the soil, where it will decompose to improve structure and fertility.

5. Mulch like mad

Given our harsh climate, it’s important to always mulch over any bare soil. This acts as a protective blanket to help conserve soil moisture which would otherwise be lost from wind and hot sunlight. Mulch can also help reduce erosion during heavy rains. And if you choose a fine mulch, like lucerne, pea straw or sugarcane mulch, this will act as another source of organic matter as it breaks down over 6-12 months.

ASK THE SOIL DOCTOR

ANSWERED BY DR. UWE STROEHER PhD. MICROBIOLOGIST

QUESTION: 

What are soil probiotics and how do I use them?

ANSWER: 

The easiest way to think about soil probiotics is much like a probiotic used for human gut health. The key similarity between the two is that probiotics aim to maintain and enhance microbial diversity over a long period, whether in the soil or in the gut. The bacteria and fungi in soil perform a wide range of beneficial functions that support plant health, including increasing nutrient cycling, promoting plant growth by producing growth enhancers, and suppressing disease. But for all this to occur, you need not only the right balance but also a high level of microbial diversity. Because soil microbes perform such varied roles, a soil probiotic should contain as many different species as possible.



A broader microbial mix also increases the likelihood that microbes will survive and thrive in your specific soil type. Regular use of soil probiotics on a seasonal basis is recommended, as shifts in soil conditions between seasons can affect microbial diversity. Probiotics are also helpful whenever you're planting seedlings or new plants, ensuring roots are supported by a rich and diverse microbial community. A critical part of using any soil probiotic is minimising its exposure to UV light, so always water it in well after application. Microbes also need a food source to survive and multiply, so organic matter in the soil is essential for building and maintaining a healthy soil microbiome