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Soils ain’t soils

Terry O’Shea – Group Director

I really hate that catchphrase but it fits the bill as the waste-based soils available on the market are generally not really soil at all. They consist of a high percentage a partially composted green waste and some so-called mineral, sand or ‘site soil’. Ok, they masquerade as passing AS4419 which defines them as soils while some manufacturers do indeed pass the test inconsistently but that is not the whole story.

So some landscape soils may pass the Australian Standard AS4419 test from time to time but the testing regime conveniently neglects the predominant ingredient, the partially composted green waste. This component really is the most important portion which dictates the general quality of the soil. Why? Because the compost component of a manufactured soil dominates the mix and itself should be tested under another Australian Standard AS4454 for Compost. This test gives a comprehensive analysis of the compost itself, so if it does not pass this test then how can it be part of a ‘good’ soil even though the resulting mix passes AS4419? For example, you can mix real dirt that initially fails AS4419 because of the low percentage of organics with as little as 5% by volume of fresh sawdust or green waste and it will probably pass AS4419. Go figure!

Quite simply, if the compost is ‘wrong’ then so will be the soil. This is a fault in the Australian Standards system and allows producers to make poor quality soils displaying the AS4419 ticks of ‘so-called’ quality assurance. It’ a real issue in the industry and it must be addressed. We are doing just that with our new UltraGrow Collection of waste-free but nutrient-rich living soils and potting mixes by controlling every ingredient, production and analysis.

Don’t get me wrong, the AS4419 standard is a good basic assessment required for manufactured landscape soils. Though criticised by many in the industry, as a basic standard it is not all that easy to pass and simply passing it does not guarantee a product suitable for supporting good plant growth. That’s is probably why it’s criticised and why most soil manufactures don’t get the test done on a regular basis. It’s also reasonably costly which is another deterrent to regular testing. But more importantly, it neglects the quality of the composted organic component which is critical for a healthy soil that supports vigorous plant growth. Isn’t that the whole idea?

What did I just say? The soil should support healthy plant growth. Gosh, that’s a novel idea! I must admit, I am being slightly harsh as some manufacturers do use clean streams of organic materials to produce reasonable soil mixes. However, I don’t believe the industry in general places enough emphasis on the quality of the composted material as they focus on recycling the huge waste streams of organic and inorganic materials that just keep on coming.

Green organics are a great resource for composting if handled correctly. But we have a long way to go to change the current culture. I have a simple view. Why spend all this money on sustainable compost recycling, and get it wrong?

Cheers for now and enjoy digging & planting in your garden landscape.

Terry O’Shea

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