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  • Writer's pictureGlenn Christie

Can You Grow a Soil in the Arid Zone?

Let’s grow a #soil; not just in the #AridZone, (pretty hot, pretty dry, pretty salty…sound familiar?); let’s build a soil from scratch on top of 8 metres of ash…


Let’s just use 6 tonnes of coloniser #seed & #rainfall; no soil amendments/additives…


What?! NO irrigation? NO fertiliser? NO gypsum?


That’s a HUGE (t)ask isn’t it?


We like a challenge, a bit of “character building” here at Succession Ecology Pty Ltd.


So, a little bit of background...


Where is this site? What was there before?


Answer: 3 coal fired power stations, (built in 1954, 1965 & 1985 respectively) which operated on this site in Port Augusta, South Australia, until May 2016.


What does a coal fired power station make a lot of?


Answer: (apart from electricity), a LOT of ash!


At the time of closure, the Ash Dam, (where all the ash was stored), covered an area of 273 hectares; (170 Adelaide ovals!).


On the surface it looked like this, (photo in top right).


A 30 hectare Borrow Pit was started in early 2017 to supply 700,000m3 of material to provide a 15cm deep “cap” for the Ash Dam.


Why? The ash was 8 metres deep & nothing grew there; not even weeds, (remember that first photo?)


Lesson from the Arid Zone: if weeds won’t grow, you’ve got a problem (soil).


The seeding of the 6 tonnes started in June 2017, (see second photo; yep, 273 hectares sown in 10 days using standard farm spreading machinery).


Remember; no irrigation; no soil amendments; no extra seed or planting; just that initial 6 tonnes…& what the “rain gods” would deliver.


So, where are we up to?


The #seeding now has an average of 12.04 plants/m2.


And? This means?


This means that the 2017 seeding has 120,400 #plants per hectare.


120,000 or so plants per hectare , looks like the third photo….


What does this all result in? The site is thriving after 5 years; it’s thriving because it’s making its own seed, it’s own plants, it’s own insulation, (protecting those vulnerable roots; remember; only 15 cm of material provided).


This is all very nice, but how is all this plant material going to grow a soil in the Arid Zone?


Good question;


The site is “housing” trillions of tiny grazers; ants, termites, beetles, earwigs, earthworms, slaters, grasshoppers; that are all feeding on the 120,000 or so plants per hectare, (& their roots).


There’s spiders, birds & lizards all feasting on this staggering amount of grazers; a veritable food chain of frass, moulted skins, leaf litter, too much seed to poke a stick at…


Plants being powered by the sun; plants being eaten by gazillions of tiny grazers; all this enabled by rains…pretty good/cool, eh?


What does all this life result in?


Soil; soil being grown in the Arid Zone.


Can you imagine the implications?


Thoughts?


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