Make your garden thrive: tips for healthier soil
Sydney's Inner West has been found to have high levels of metal in its soil as well as a tricky soil texture but that doesn't mean your garden can't thrive. PhD student Liana Johnson shares simple tips to improve soil health.
An analysis of soil contamination has found the highest lead concentrations in Sydney exist in residential areas.
This research was conducted by University of Sydney PhD student, Liana Johnson, from the 听in conjunction with听Associate Professors 听补苍诲
focused on the Sydney estuary catchment (with Parramatta River at its centre) using state-of-the-art geospatial data and statistical models.
鈥淭he biggest area of concern was to the south of the catchment, in Sydney鈥檚 inner west.鈥�
Soil contamination in Sydney
鈥淲e found that 5 percent of this area had a predicted topsoil lead concentration exceeding the safe guideline for residential soil (300 mg/kg),鈥� said Liana.
鈥淭he biggest area of concern was to the south of the catchment, in Sydney鈥檚 inner west.鈥�
Other areas of concern lie closer to Sydney鈥檚 CBD where there has been significant pollution.
鈥淭his area contains older houses, which up until 1950 were coated in paint containing high amounts of lead.
鈥淓xhaust fumes from traffic was also a large contributor to lead contamination in soil adjacent to roadways prior to the ban on leaded petrol in 2002.鈥�
What鈥檚 causing high lead concentrations?
Soil has been significantly impacted by the human population and activities over time.
鈥淭he presence of heavy industry in parts of Sydney and other cities around the world has had a direct impact upon the soil.听 Another factor is cars themselves. Emissions, brake pads and tyres all contribute,鈥� said Liana.
It鈥檚 normal for soil to contain low concentrations of heavy metals, it鈥檚 just the high readings that communities need to be cautious of.
鈥淭here is no such thing as 鈥榖ad soil鈥�,鈥� said Liana. 鈥淎ll soils have a purpose and can still foster growth 鈥� they might just not be as healthy for humans so it鈥檚 important to know about soil health.鈥�
In light of contamination findings, homeowners need to be aware of how they can manage soil health to ensure a safe backyard for their families. Likewise, increased knowledge of soil conditions will give gardeners a better chance to have their plants thrive.
How to assess soil health
Become a detective. Look out for obvious indicators within your garden and assess your local surroundings.
If you are concerned, Liana recommends purchasing a lead test kit from a hardware store or online. Alternatively, you can get your soil tested by a laboratory so you know for sure.
Sydney鈥檚 soil types
鈥淭he type of soil you may encounter is often linked to the underlying bedrock. The bedrock in Sydney is mostly sandstone and shale. Areas upon sandstone are likely to have sandy soil, while areas located over shale are most likely to have clay based soil.
鈥淣either of these two natural soil types in the Sydney region are particularly rich in plant nutrients.鈥�
Each soil type has pros and cons.
鈥淪andy soil is well drained, but it also means nutrients can be washed out, while clay soil has poor drainage and can be easily compacted. This makes it harder for plant roots and organisms to move through the soil.鈥�
In an ideal world, a combination of these soil textures will provide optimal conditions for plants and soil organisms, along with a healthy dose of organic matter.
Ways to improve soil health
鈥淎dd compost,鈥� said Liana, 鈥渢his organic matter contains much needed nutrients for plants and soil organisms to survive and grow.
鈥淎pplying it to sandy soil can also help improve soil moisture and help retain nutrients for a longer period of time.
鈥淚f your soil is a heavy clay meaning it traps a lot of water, is hard to dig in, or plant roots can鈥檛 spread, it can help to add gypsum to help break up it up.鈥�
Liana suggests that gardeners should be wary using pesticides as this too may negatively impact the soil. Instead you should introduce plants which encourage beneficial insects to help control the pests.
鈥淚nsects help break up the soil, and depending on the species they can help to break down organic matter (e.g. the Dung beetle), or eat other insects (e.g. lady bird eating aphids 鈥� a common garden pest).鈥�
Provide optimal conditions for soil organisms such as this and you will help your plants thrive.
鈥淓arthworms break down organic matter, turning it into a source of food for plants. They also break up the soil and aerate it, providing air for the millions of helpful microbes living in the soil.鈥�
Keep your garden safe
鈥淚f your topsoil has high concentrations of heavy metals, the biggest concern is ingesting or inhaling the soil 鈥� especially if there are children playing in the yard,鈥� said Liana.
鈥淚t鈥檚 a good idea to avoid leaving areas of exposed soil. Covering the area with turf can help.鈥�
Plants can also be a great way to absorb metal contaminants Liana suggests, with many known species being able to withstand high metal concentrations in the soil.听
鈥淭hese plants are known as 鈥榟yper accumulators鈥�, examples include Pig face, which absorbs cadmium, and Bracken Fern which is able to accumulate high amounts of arsenic.鈥�
It鈥檚 still possible to have a veggie garden in Sydney too.
鈥淐oncerned veggie gardeners should use lots of compost on the garden which can capture the metals present, preventing them from being absorbed up by the plants.鈥�
鈥淚f metal concentrations in the soil are very high, veggies should be grown in raised garden beds filled with clean soil to prevent plant roots taking up the contaminants.鈥�
鈥淲e also recommend rinsing veggies before use.鈥�
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