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December 2009
Welcome to the December 2009 edition of Fertile Minds, the newsletter of Sydney Environmental & Soil Laboratory.
In this issue we comment on the NSW State Government’s proposal to replace productive farms in Sydney’s west with yet more houses.
If you have any questions you would like answered in Fertile Minds, please write to info@sesl.com.au. If you have any special requirements, we would be pleased to talk with you and tailor a package and price. Please contact the office on (02) 9980 6554 or write to us at info@sesl.com.au.
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In this issue
- The Loam Ranger – Soil remediation
- Loss of prime agricultural land in Sydney Basin to urban sprawl
- Contaminated fill – don’t risk a fine!
- Recycling irrigation runoff
- Hilton Hotel “green wall” reinvigorated
- Did you know ... ? – Perlite
The Loam Ranger – Soil remediation
Our reader Lynn Collins sent us this query:
I found the cadmium item useful as, following analysis of our garden soil with your company, we have a bit of the stuff polluting what was our veggie patch, along with other nasties.
- The soil we inherited is polluted with benzopyrene, lead, PAHs and zinc (and, sadly, but to a lesser degree, manganese, copper and arsenic) and we’d like to assist Mother Nature [to] repair this soil – any suggestions for neutralizing agents; stimuli for organic agents going about their regenerative/curative work; plants that might absorb. I had heard that water hyacinth and bracken may be particularly useful cleansing plants: an old wives’ tale?
- Are home-kits available for ongoing testing of areas of the garden for poisons? I noticed a basic lead-sensing device in the paint department of my hardware store the other day.
- Are fruit trees – say, orange, banana, blueberry, plum – likely to uptake lead and other poisons in a season’s crop sufficient to harm (very young) humans?
Avoiding the problem
The first question you need to answer is whether it is even necessary to remediate the soil. If you would like to reuse your former vege patch to grow veges again (because it has a good aspect, for example), you can use the raised-bed design favoured by Peter Cundall, formerly of Gardening Australia, by organisations that cater to the disabled and elderly (e.g. Sustainable Canberra), and by the late Esther Deans in her “no-dig” gardening design.
If you don’t intend to use the garden to produce food, the question then becomes whether anyone is likely to ingest any soil. If you have a crawling baby who likes to eat dirt (a behaviour called pica), obviously this is a concern, and it will be several years before any child playing in the garden stops getting caked with dirt (which then goes into the mouth with food). A simple solution to this is to turf the area or otherwise plant it with groundcovers that will prevent access to the soil.
Remediation
If you really are keen to remediate the soil, the key factor is bioavailability: how available are the contaminants to plants (and thus humans)? Many heavy metals can be rendered unavailable to plants by adjusting the soil pH to above 5.5 (usually with lime). Plants then can’t take them up (or take up less).
Click here for full details of soil contaminants and remediation (1400 words, 6 minutes)
Loss of prime agricultural land in Sydney Basin to urban sprawl
In a recent interview in the Sydney Morning Herald, Adrian McGregor, of McGregor Coxall, one of SESL’s clients, is quoted as saying that the NSW State Government’s Sydney Metropolitan Strategy proposes to allow as many as 400 000 new homes to be built on prime agricultural land (640 000 in all). The strategy fails to take into account the value of agriculture in the Sydney Basin, the vastly increased costs if we have to truck our food from further west, the impact of climate change and the increased likelihood of inland droughts.
If the strategy goes ahead in its current form, it will replace more than half of the remaining 1052 farms (totalling 2025 ha) with houses in the proposed Southern and North-West Growth Centres.
The strategy lists seven key strategies for development. Food isn’t one of them. What, then, shall we eat?
Value of Sydney Basin agriculture
A 2003 estimate put the value of agriculture in the Sydney Basin at $1 billion (thousand million), with a multiplier effect of 4.5: that is, it creates a total value of $4.5 billion. Further, the Sydney Basin provides:
- 80% of Sydney’s fresh mushrooms
- 90% of Sydney’s fresh vegetables
- over 90% of cut flowers sold through the Sydney markets
- nearly 100% of Asian vegetables sold at the Sydney markets
- a large amount of stone fruit, apples and oranges
- most of Sydney’s fresh tomatoes
- 1/3 of NSW’s poultry production
- more jobs than any other single industry employer in western Sydney.
In addition, Sydney Basin farms return $5433 per hectare, 40 times the state average. Do we really want to give up all of this production and employment?
Contaminated fill – don’t risk a fine!
Through our interactions with out clients, we’ve learned that a lot of people remain unaware of the new legislation covering the use of landfill in NSW. Because breaching this legislation can result in fines of up to $1 million, and we don’t want to see any of our clients do the wrong thing, we’ve put together this article to outline the basics of compliance with the law.
Why it’s regulated
- Because much fill that has been offered as “clean” has turned out to be contaminated with poisonous chemicals.
- To prevent the contamination of home sites, parkland, bushland, groundwater and waterways with poisons leached out of contaminated fill.
- To crack down on shonky dealers looking for a quick buck at the expense of the unwary.
“Clean fill” no longer
The term “clean fill” has no legal standing. Fill cannot be offered as “clean”. It can, however, be offered as “virgin excavated natural material” if it meets the definition.
Click here for advice on approvals, documentation and testing (650 words, 3 minutes)
Recycling irrigation runoff
As water becomes more scarce in Australia’s increasingly drier climate, we have to find more ways of making better use of the water we do have. Recycling runoff provides an excellent way to get more out of this water.
Unfortunately, simply collecting runoff (for example, in drainage canals or dams) and pumping it back is not enough. As water runs over and through soil, it dissolves salts and nutrients. The more times it is recycled and collected, the more it picks up.
Salts cannot be removed from water (except by prohibitively expensive desalination treatment), so we have to find ways of coping with what’s there. Depending on your situation, you have a number of options.
Click here for options and for legislative requirements (500 words, 2 minutes)
Hilton Hotel “green wall” reinvigorated
Sydney’s Hilton Hotel, built in 1969, was for several decades a triumph of concrete over style. In 2000, it was redesigned to improve both its look and its patronage. In July 2005, it was reopened with a radically improved design. One striking feature of the new design is a “street” that passes through the hotel between Pitt and George streets. This street brings visitors into a courtyard and a glass-fronted main entrance, opposite which a vertical garden cascades 11 storeys.
TLC Indoor Gardens installed this “green wall”, planting Cissus rhombifolia. When first installed, it looked eye-catching and grew well, but around 12 to 18 months later it started to decline. The landscape architect called in SESL to investigate in 2008 with a view to reinstalling the green wall.
We found that the normal organic potting medium they had used had decayed and collapsed, causing waterlogging. So Simon Leake, a member of the Australian Standards potting mix standard committee since 1989, designed a special-purpose long-lasting mix using highly specialised components not normally used in the potting mix industry.
Click here for more details and a photo of the new green wall (400 words, 2 minutes)
Did you know ... ? – Perlite
Perlite is the white crunchy material we see commonly in potting mixes. In the wild, it is a volcanic glass (an aluminosilicate) with a water content of 2% to 6%. Raw perlite is typically greyish or brownish, but can be shades of other colours.
On heating to above 850 °C it melts, and the trapped water expands in a flash, puffing up the glass. A similar process creates popcorn and puffed rice. The myriads of trapped gas bubbles repeatedly reflect the light, giving expanded perlite its brilliant white appearance.
Before expansion, perlite has a bulk density of 2.2 to 2.4 g/cm3. After expansion, its density ranges from 0.055 to 0.3 g/cm3. This represents an increase in volume of anywhere from 7 to 40 times.
Click here for more info on the uses of perlite (300 words, 1 minute)