10 Feb 2024

Organic gardener Kath Irvine: all you need is compost

From Saturday Morning, 10:40 am on 10 February 2024

Compost is the heart and soul of the food garden, says Edible Backyard gardener Kath Irvine.

And homemade compost really is the ultimate, she tells Susie Ferguson.

“The powerful thing about homemade compost that's very different from bought compost, from the myriad of bought fertilisers you can buy, is that it's full of life and that's super important.

“That's the key to less disease, a lot less pests and steady, abundant cropping, which is what we're all after. That's everyone's dream. That's our dream garden.”

Kath Irvine on the porch of her house truck

Kath Irvine Photo: Kath Irvine

Be wary of bought compost, Irvine says.

“Have you ever walked past a stack of compost bags and it’s got a bit of a yucky wiff? That really is honest to goodness, a very good judgment.

“Compost, ideally, should never be bad. In my dream world, compost would all have a date on it. And even with a couple of little holes in the bag.

“It's a living thing and it's been suffocated and then if you stash it in the sunshine outside, like lots and lots of bought compost bags are, it's even worse. It's just putrefying and quite frankly becoming dangerous.”

Commercial compost also uses inputs that may be full of damaging herbicides and fungicides,she says. If you buy commercial, her advice is to buy organic compost that has been stored in the shade.

You can set up a garden that needs a lot less fertilising, Irvine says.

“Simple things like cosying up and positioning all your fertile things, or your fertile places together.

“So, your citrus trees, your veggie garden, your greenhouse, if you have chickens having those close by and your compost bins all in the same space.

“That's very simple that the fertility spreads from each area and greatly reduces your composite needs.”

Another strategy is to surround your veggie garden with perennial companions, she says.

“This is where we tap into the benefit of that incredible life force below ground that is actually the providing the true nutrition for our veggies.

“It's not the stuff we necessarily put on top that's keeping that life going and nurtured and fed, it lives in the rhizosphere, which is the area around the roots of plants. So having perennials through your veggie garden, if it's a big garden, or around the outside, is providing these hubs of life force for which can plug in and spread out into your veggie garden.”

Her favoured compost set up is very simple.

“A really simple bin made with pallets. I think that's really cheap and easy. You can make that in two seconds flat.

“I just love to drive in some waratah metal star pickets, and slide the pallets over the top two seconds, there's your bin. Just with an open-sided front.”

This method has the advantage of bringing air to the heap, she says.

“I'm not a fan of those black plastic bins, not enough air. For most places, if you have three or four of those pallets side-by-side on the edge of your veggie garden so the garden can also be benefiting from that fertile that runoff from your compost bin, that will be enough and that will really do you.”

Compost boxes with composted soil and garden waste for backyard composting

Photo: 123RF

Make your compost in such a way as it needs no turning, she says. This saves time but it means getting the ingredients right at first.

“Over the years, I've evolved to no turning because I'm really wanting this to fit into a busy person's life. And it takes longer, but actually if you have lots of air coming from your compost by itself, and if you're using a lot of coarse, dry matter in your compost itself, that also brings the air in, that coarse, dry stuff is the thing that is missing from nearly every compost heap, I visit or I consult with people over - it's that coarse stuff.”

After that, it’s all about variety she says.

"The best thing to make the bulk of your compost with is your good old garden waste. It's a good balance of green bits and stalky bits and nice chunky hollow stalks like your borages. Coarse stuff and fine stuff.”

Most home gardens end up light on brown carbon-rich material to balance out the abundant green stuff, she says.

“If you get if have too much of the green stuff you just end up squashing, there's no air and the and you just end up with a putrefying, stinky sludgy mess at the end which is a little disheartening.”

She tends to make a heap in one go, she says. Starting off with a layer of thin twigs to bring air and fungi to the heap.

“The way I like to make compost is to have a big old garden clean up. Don't worry about cleaning up your garden until compost making day, and go round any spent crops, or anything blocking the pathway or crops that are falling over top of other crops, all that kind of stuff, do a bit of deadheading and just walk around with a wheelbarrow and chop everything into it as you go round.

“The smaller you chop up, the better the bit of the breakdown. Take that back to your compost bay and tip it out mix it all together and assess it.

“Maybe you think, it needs some more dry stuff. There's too much fine green stuff.”

Stockpiling dry brown materials such as leaves or hay is a good idea, she says, so you can easily tweak the mix.

Then add in something mineral rich like perennials or seaweed, she says, and keep it covered.

Food scraps are best avoided, Irvine believes, unless you’ve generated a lot through preserving and you mix that all though the heap in one go.

“Food scraps are dense and heavy. Making compost is a very sensory thing, it's a feel that you get for it. And the end product you want to be quite airy.

“It's got some nice moisture, but it’s nice and airy.”

Go with a Bokashi bin or worm farm for your kitchen scraps, she says.