Mulch and compost

To buy or not to buy, that’s the question.

Now that we’ve got some idea of what vegies to sow when, we’re starting to think about how to find enough mulch, seed raising mix and compost to keep them all going. When we lived in the suburbs, the only option was buying in everything – you can’t really grow enough mulch on a suburban block, unless perhaps you tear down your house and grow mulch there instead. But here – woohoo! – we might be able to make our own somehow. So…


Not that long ago, we discovered that if we whippersnip a uteload of grass in the paddock, we have about a week’s supply of mulch for the garden and the chook coop.  What fun!  I have a great photo of Felice standing in front of a uteful of grass, looking aghast after spending the afternoon raking to the noise of the whippersnipper.  Unfortunately, she won’t let me put it online.  Whippersnippering and raking is fun for the first 30 mins or so, then not.

But wait – is there a better way?  Could we either:

  • dispense with the loud fossil fuel whippersnipper, and use a scythe?
  • use an actual lawnmower with a catcher, so we don’t have to rake up all the cut grass?

The jury is still out on both of these.  If anyone has sage advice, please feel free to comment.

And by taking grass out of the paddock to put on the garden, are we taking too many nutrients from the paddock soil?  So far, we’ve only been whippersnippering the overgrown 4wd track around the outside of the paddock.  And there are deep-rooted trees nearby that bring up nutrients from way down in the soil and drop them in the form of leaves on the paddock.  But clearly, continuous removal of grass can’t be good in the long term.  So do we:

  • keep taking the grass and bugger the nutrients?
  • buy in mulch, spending money (and not being particularly self-sufficient) but also saving time and actually adding nutrients to the property, instead of just moving them around?
  • grow mulch plants nearer to where we need the mulch (ie near the fruit trees, summer garden, chook coop), thus cycling nutrients vertically (sustainable and useful) rather than shifting horizontally (unsustainable and hard work)?

We’ve decided for now to try growing mulch plants closer to where we need the mulch: (constrained) comfrey, and legume cover crops on/near garden beds and lemon grass/lomandra on contour on the slopes.  While the plants are still growing, we’ll continue to clear the road of grass (might take some time!) with a view to eventually getting some animals (maybe a couple of Dexter cows?) to mow and compost the grass for us.  We also currently have more blady grass patches than we would like, so we plan to use those as mulch until we can replace them with something less flammable.

Any thoughts by anyone welcome.  Especially if you know about Dexters.

This is a story about compost, but also about marketing and trust in authorities.  About 3-4 months ago, we were struggling to make enough compost for the garden. Our soil here is quite good, but could do with a heap of organic matter added.  We were establishing the summer garden, and needed a lot of compost now.  Do we buy it in?  or do we keep putting off sowing until we’ve made enough compost to take care of the ones already growing?

It turns out that there’s a worm farm associated with Lismore tip.   It sells vermicompost, made from Lismore residents’ green waste, by the ute load.  We decided to go and have a look, and the man in charge there was very helpful and answered all our questions patiently and gave us a good price.  Yes, the chemical analysis of the vermicompost satisfied all the criteria for a NASAA certified organic “soil conditioner”.  Yes, some of the composts have lots of little bits of plastic in them, but here’s one that has less.  The vermicompost has more nutrients than the plain compost but costs a bit more. And so on.

But here’s the thing: when we got the uteload of vermicompost home and had a good look at the results of the chemical analysis (and then a google), we found that:

  • our vermicompost had a lead concentration of around 150 ppm.  Lead (Pb) is a toxic heavy metal and a cumulative poison.  I’ve spent a fair bit of time at a couple of unis doing research on environmental lead, so it’s the first thing I look at in an analysis.
  • the NASAA criterium for safe Pb concentration for a soil conditioner is 250 ppm.  So our vermicompost, as promised, satisfied the NASAA guidelines for a soil conditioner.
  • the NASAA criterium for safe lead levels in garden soil (as opposed to soil conditioners) is 100 ppm.  So if we kept buying the vermicompost and adding it to our garden, eventually we would fail organic certification.  We don’t necessarily want to be organically certified, but we do want our garden to be organic, and the NASAA guidelines are a good place to start when it comes to levels of contaminants.

So we decided that buying in Lismore vermicompost is not practical for us.  Perhaps what we need is a compost suited to use as a garden soil, rather than simply an amendment?  That would at least have a Pb concentration of less than 100 ppm.

But then we looked further at the NASAA guidelines.  We knew that:

  • background levels of Pb in soils (ie those occurring naturally, and with which our bodies have evolved) are generally below 50 ppm.  Carl Rosen, a soil scientist at the University of Minnesota, wrote in 2002: “Background concentrations of lead that occur naturally in surface agricultural soils in the United States average 10 parts per million (ppm) with a range of 7 to 20 ppm. Soils with lead levels above this range are primarily the result of lead contamination.
  • Pb in soil is taken up in varying amounts by plants that grow there.  Vegetables tend to take up more lead than say, citrus trees.  We’re planning to grow vegies in our garden, not citrus.  And we intend to eat them, ie ingest any Pb that they’ve taken up.
  • according to Wikipedia, “No safe threshold for lead exposure has been discovered—that is, there is no known amount of lead that is too small to cause the body harm.

So why is the NASAA guideline double what the naturally-occurring levels are likely to be?  Seems a bit odd.  Can that be right?  I don’t really want to ingest any more Pb than my body has evolved to deal with – that’s why when I couldn’t grow my own food, I’d buy organic, in the belief that it was essentially free of heavy metals and other contaminant toxins.   But it seems that my idea of “essentially free” is different from that of one of the most stringent certifying bodies in Australia.  And if “organic” food is allowed to grow on land with up to 100 ppm Pb, what kind of levels can industrial agriculture soil contain?

I don’t want to scare anyone away from eating organic  food – of course it’s way less likely to have toxic levels of contaminants/residues than non-organic.  (I couldn’t even find a standard for Pb concentration for non-organic agricultural soils – does anyone know if one even exists?)

And I certainly don’t want to scare people away from growing their own food in their backyard.  If you have your backyard tested, you know exactly how much lead there is (or isn’t) and even if you don’t, you can take some simple steps to reduce your lead exposure. Far better to grow your own, with lots of organic matter to lock up the lead in the soil, than buy industrial ag food for which the lead safety soil guideline is either non-existent or very hard to find online.

It’s just that putting blind faith in certifying bodies (who have an interest in making it easy enough to certify that farmers will go through them rather than a different certifying body) may be leading to standards that aren’t as stringent as people think.

So, we decided against buying even a 100 ppm Pb “garden soil” compost.  Dammit!  The problem is not the Lismore worm farm, or the helpful man in charge.  Both appear to be operating according to standard “best practice” – all their soil is tested to conform to guidelines.  We just found that our idea of what guidelines are appropriate are different to what the packaging says is appropriate.  Paranoid?  Depends on who you talk to.

So perhaps we could go one step back in the chain, and buy the ingredients for our own home-brewed compost.  That way, we could avoid potentially contaminated green waste from Lismore residents, as well as cutting down on the time-consuming process of gathering/shredding/shovelling materials to compost.  But – arrg! – it turns out it’s also really difficult to find out where most commercial compost materials come from.  So how can you know what’s in them?

The situation reminded me a little of the time I wanted to buy something called “organic cow manure (guaranteed chemical free)”.  I phoned up to order and just offhand asked the lady where it came from.  Lucky I did.  “Oh, probably feed lots out west, I’d imagine”, she said.  What?  How is it organic then?  “Well, it comes from cows.  They’re organic.”  I see.  And how can you guarantee it’s chemical free?  “Well, we don’t add any chemicals to it.”  Aha.  I’d fallen for the old “define-it-differently” trick: use a word that most people think of as meaning one thing, but actually mean it to refer to something else.  Then when you’re caught lying, you can point to the obscure meaning, which is technically true.

I felt pretty stupid.  I’d even had direct experience of the wide variety of ways people use the words “chemical” and “organic”.  I spent a few years being a chemist, and to a chemist, pretty much all matter is made of “chemicals” – pure water, oxygen, wood, even unleaded compost.  And “organic” means containing lots of carbon and hydrogen, and often manipulated in a lab to produce something of industrial or pharmaceutical significance.  After much resistance, I’d accepted the use of “chemical-free” to mean “not having industrially-produced/petrochemical-derived/toxic chemicals added”, and “organic” to mean something like “certified as chemical-free by an organic certification body”, but still I get a little trembly when I use the non-chemist definitions, because I remember how I used to see things.  So I should have sussed the “define-it-differently” trick a little quicker.

But I’ve learned my lesson, and now when I see a bag of cow manure labelled “Organic!!!” I don’t fall for it until I’ve read the fine print.

So after all that, these are the main ingredients we’re currently using in our home-brewed compost here:

  • shredded lantana and other bits and pieces we’ve cleared from our own gardens and paddock.
  • cow poo we’ve shovelled from properties of people we know don’t spray.  We compost it thoroughly to try to eliminate any residues of worming drenches.
  • used chicken straw from our “girls” (sorry – “ladies”)
  • kitchen scraps that the ladies turn their beaks up at

It’s bloody time-consuming gathering all that, and we’re getting a lot of practice at shovelling poo, but when you buy compost, or even just ingredients for compost, our experience has been that it’s ridiculously hard to find out for sure what’s actually in the stuff you’re buying to put on your garden.  If anyone ever starts selling compost with no contaminants, and you can prove it, please contact us and we’d love to support you.

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2 Responses to Mulch and compost

  1. Rebecca says:

    If you’re desperate for mulch, pulled weeds can be left to rot on the ground. Just make sure they haven’t flowered yet or you may end up with more weeds than you had. Paper (ripped up, or shredded if you have a shredder) also works well in a pinch, although it’s better in the compost, I find. Compost (once you’ve got yours really going) is a great mulch, especially on top of your grass clippings/pea straw/paper, etc. I put half rotted compost on top of pea straw/grass/old paper around my fruit trees and it’s like having a mini compost heap around each tree.
    Another thing, I’ve heard that comfrey is a great compost activator when you want it all to start rotting in a hurry. Tansy and nettles are great, too. Just a few leaves are enough. You could plant some comfrey next to your compost so it’s always handy. Tansy’s a good one for your chooks, too.

    Hope this helps!

    • Felice says:

      Hi Rebecca,

      Thanks for all your wonderful suggestions. Piling on the weeds works well.

      We’re slowly getting on top of the compost situation having simultaneously discovered an ongoing supply of cow and goat poo, as well as sawdust.

      What a joy!

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