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August 2008
Welcome to the August edition of Fertile Minds, the monthly newsletter of Sydney Environmental & Soil Laboratory.
Spring is here. Have you sent off your soil and tissue samples for analysis yet? If you've already got your results back, now is the time to implement any improvements before your plants start growing again. If not, then what are you waiting for!
If you have any questions you would like answered in Fertile Minds, please write to info@sesl.com.au. Or 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 – Changes to the NSW Protection of the Environment Operations Act
- Corrosion, aggressiveness and scaling assessment
- Urban toxicity
- Soils and tree roots: key requirements for tree health
- Did you know ... ? – Maximum rooting depth
The Loam Ranger –Changes to the NSW Protection of the Environment Operations Act
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Dear Loam Ranger, I've heard that the NSW laws covering waste reuse have changed, but I can't find a clear explanation. What do the changes mean for me? Changes to the NSW Protection of the Environment Operations Act 1997 (the POEO Act) took effect from May 2008. The intention was to simplify waste classification in NSW and to specifically prevent any waste from being placed on land as fill or as fertiliser without a licence, even where the waste has been extensively reprocessed, for example into compost. The only exception was where the waste is sold as complying with the NSW Fertilisers Act 1985.
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Corrosion, aggressiveness and scaling assessment
Corrosion is most commonly the conversion of a metal to its oxide and consequent loss of strength and function. The most familiar form of corrosion is rust, which is a mixture of oxides of iron. Other metals can also become corroded, but rust is the biggest problem, both because iron is the commonest construction metal and because of the way iron rusts: Iron oxides take up more room than iron, and so rust expands, cracking structures.
Aggressiveness is the propensity of a soil or water to dissolve cement structures. This is mostly a function of total salt load, the sulphate level and the acidity.
Scaling is the deposition of insoluble salts, oxides and hydroxides from water on surfaces. Inside pipes, this can block flow. Common scaling substances include calcium carbonate, calcium sulphate, magnesium hydroxide and iron oxides.
The durability of concrete, steel and other metal structures is influenced by the soil and water environment. The corrosion or scaling potential of soil and water poses important limitations on how structures are built.
Urban toxicity
Despite the steady market in complete fertilisers, trace element deficiencies in urban areas are so rare as to be negligible. In fact, the fertilisers are part of the reason. We at SESL almost never come across trace element deficiencies in Sydney and other urban centres. The modern lifestyle has a lot to do with this situation.
In addition to deliberate application, plenty of trace elements have been added unintentionally. An excellent example is zinc. There are two major sources of environmental zinc: galvanised iron and car tyres.
Click here to see why urban soils are chock full of trace elements (500 words, 2 minutes)
Soils and tree roots: key requirements for tree health
The soil gives a tree's root system five critical requirements: oxygen, water, nutrients, space to explore and anchorage. Soil compaction through human and livestock activities is detrimental to all of these, and thus to tree health.
Click here to read how soil compaction harms trees (500 words, 2 minutes)
Did you know ... ? – Maximum rooting depth
The roots of a wild fig tree (Ficus natalensis) at Echo Caves, near Ohrigstad, Mpumalanga, South Africa, reach 120 m deep (Guinness World Records).
Even apart from this record-holder, though, many species regularly put roots down to more than 10 m, and specimens of Boscia albitrunca (the shepherd’s tree) and Acacia erioloba (the camel thorn), both of which grow in southern Africa, can put down roots to more than 60 m.
Pine tree roots revealed by erosion along the Waimakariri River in New Zealand (photo by Murray Fraser)
Click here to read about the benefits of increased rooting depth (700 words, 3 minutes)