Sunday, August 9, 2009

Compost recipe

Last night we had some friends around for dinner and I cooked a Moroccan-style tagine recipe called 'Lamb Tagine with Seven Vegetables', served with couscous. So this morning my vegie scraps bin was almost looking photogenic, which is not the word you'd usually use to describe it! And the thought soon popped into my head that this would be as good a time as any to do a little blog on the recipe I use for cooking up compost here in Amateur Land.

There's all sorts of things in here: carrots, beans, onions, garlic, zucchini (courgette), pumpkin (no seeds though), turnips, chick pea husks, strawberries, scraps of mint, coriander and parsley, plus apple and pear cores, a banana skin, tea leaves, coffee grounds, etc.

And this is where it goes: into the tumbler bin. The problem with all these lovely scraps is that they are a bit wet, and also a bit acid, too. Hence the need for a compost 'recipe', as the vegie scraps are the things most commonly added to this bin.

Next ingredient: dry stuff, in this case two handfuls of sugar cane mulch, the cheapest and most plentiful mulch available here in Sydney. Sometimes, if I could be bothered, I use shredded office paper, but mostly I go for mulch, as it's in a big bag in the shed, about 10 feet away, and it's easy. Shredding paper is very boring, and I don't think it's as good as mulch at soaking up moisture, anyway. Dry leaves are another option, if and when you have them. So, virtually every time I add a bin of vegie scraps, I add a few handfuls of mulch, as well.

Next ingredient is a good heaped handful of dolomite lime. This 'sweetens' the mix, keeping its pH closer to neutral. Before I got onto using dolomite, my composts had alarmingly low pH levels, which acidified the soil here, which is inherently acid anyway. I don't add the lime every time I add a bin of scraps. About once a month seems to be enough.

The next (and last) ingredient is air, and it's probably the most important one, in fact. I give the bin three or five spins, making sure that the end that was facing up prior to the tumbling faces down at the end of tumbling. (Not sure whether this hopelessly disorientates all the poor worms inside the bin! And there are quite a few in there, as I also add in a bit of worm-laden ordinary garden soil to help the whole composting process to get going.)

Dolomite lime is readily available at any local garden centre here in Sydney. It's just crushed rock, and looks and feels like a soft yet grainy powder. As well as using it in the compost bin, I also use it in the vegie garden regularly, when preparing beds for planting (about a handful dolomite lime per square metre, mixed in with lots of compost and a handful per square metre of chicken manure). Dolomite lime also adds good amounts of magnesium and calcium to the soil, which is generally beneficial for plant growth and health. And, best of all, its action is gentle, so it's the stuff to use. It works slower than ordinary garden lime and it's unlikely to get you into too much bother if you're a beginner by either using too much or using it near the wrong plants. The only exception to that little comment is, of course, if your soil is already alkaline. You'd be mad to add dolomite lime, or garden lime, to already-alkaline soils. In Australia, acid soils are the rule in most areas, including mine, but alkaline soils are common in some areas around Adelaide and Perth, for example, where the underlying rocks are limestone.

This is the alternative to dolomite lime: garden lime. It's faster-acting and stronger than dolomite lime, so you need to be more careful in applying it. It doesn't contain the magnesium that dolomite lime has, but it's loaded with calcium. I never add it to my compost bin, and I rarely use it in the garden, as it's a bit too heavy duty for my needs.

So that's my el-basic compost recipe.
kitchen scraps + mulch + dolomite lime + air
Mix, and repeat endlessly!


Dot said...

Hi Jamie,
I really enjoyed your post. My parent's worm farm takes care of my veggie scraps but I would love to someday do my own compost. Its a newb question I know, but what do you use to test your soil's ph?

And your right. Your scraps were quite photogenic ;)

Jamie said...

Good question, Dot, and I think I'll do a little blog entry on that to answer the question more fully. However, the shortish answer is that you can buy a soil pH test kit at any decent garden centre.

Why I'd do a blog on that is that some pH test kits are better than others. The one I use is sold by a company called Manutec, and it's the same one used by field officers in Agriculture. It's easy enough to use, but does involve about three steps to use it, but it's very reliable in its results. Some other testers, which involve prongs with dials that you insert in the ground are extremely easy to use, but not so reliable.

glen said...

I'd like to add that most of these rapitest-type PH probes sold in many garden shops don't work (ripoff I think)- you usually need to buy the real digital ones that cost more.

Jamie said...

Hi Glen
I'm not keen on any probe-style pH tester. My kit (made here in Oz by Manutec) consists of a small bottle of liquid, a small bottle of powder, and a coloured plastic chart (plus instructions). It's the same kit they use to test soil pH in agricultural settings, and it's quite simple, reliable and accurate.

To use it, you take a small sample of soil, wet it with the liquid, then dust it with the white powder, and it changes colour in 60 seconds. Match the colour to the plastic chart and you know your pH.

Yes, it's a bit more hassle to use than a probe, of course, but all the gardening experts I know say it's the most reliable way to test pH, so that's what I use.