I’ve been aware for years that to make really good compost, you need to get the right balance between materials so that you get a good ratio of carbon to nitrogen, or c:n ratio…. Why? Because it is these two elements which all the bacteria and fungi feed on in order to make your compost. Yes that’s right. Compost is a process of actively feeding a huge number of micro-organisims the right stuff in the right amounts, so that they munch and breed and munch some more, converting your pile of poo, paper, greenstuff, whatever into what we call compost. So really, it’s basic organic decomposition, accelerated by the right chemical balance so you don’t have to wait 2 years between having a pile of muck and something that can be a growing medium and general nutrient source for plants (and, therefore in turn, you).
But how to get the right c:n ratio is not something that is intuitive to most people (certainly not me) – I can’t just look at a pile of grass cuttings, or a bucket of food scraps, and say ‘Ah! Clearly that’s a 54:1 ratio right there…’ – it’s tricky… but not anymore! We have a Compost Calculator!
Nick knocked up this little Compost Calculator for us (and you) to use – its an online widgety thing that does the hard thinking for you – you just plug in what materials you have and wiggle their amounts until you get a good ratio. Then, you use those accurate amounts to make a compost pile . Ta da!
So – i went to it, using the compost calculator, and amassed my composty assets. One garbage bin’s worth of food scraps, one bin of grass+weeds from next door, one bin of straw, and one bin of used office paper from our recycling stash. This all comes out with a ratio of 21:1 – which is good. It should make quite a ‘hot’ compost – i.e. one which will heat up quickly and need to be turned more regularly – but that’s fine – in fact, that’s what I want… I need compost and I need it now, so I’m happy to use a 18-day compost method, which requires turning on the 4th day after building the pile, then every second day after that. Theoretically, in 18 days, it should be a steaming pile of goodness, ready to be unleashed on my seedlings, cuttings and general planty bits. But more on the turning later –
To make the pile, make sure you add everything in layers, like a lasagna, so that everything gets as good a mix as possible… and make sure the pile is damp, but not dripping wet – all those micro-organisims need water too, as well as all that lovely food. As a rule, make sure yr pile is at least 1meter cubed in size – smaller than this and it may not work under this method.
If you don’t have enough space to be making a 1m cubed pile (and usually you do, even if you think you don’t – unless you have less than about 3m square outside to use), I would say go find yr nearest spare block and do it there – realistically, ain’t no-one going to steal your pile of decomposing bits in the night, and someone making a pile and then covering it with a tarp in a unused space isn’t an offence, as far as I’m aware. This not only will save you a heap of money on packaged compost and potting mix, it will also get you actually working with the basics of soil and life and all that fabulous stuff, and, last but not least, you’ll get buff! Why on earth would you go to the gym or on a diet when you could just make some damn fine compost instead?
Next: the turning…..