Clever composting: what you need to know
Here are what I’ve found to be the most important things to get right when composting.
1. Experiment with compost materials
If you are like me and gather your compost materials from various sources you may find that the compost changes from batch to batch. That’s ok. It’s a learning curve of finding out what works best for you. I started using as much garden waste as possible, but found I had too much of a mix of greens and browns all in one load and also far too much soil attached to the plants (see this article for a more basic explanation of composting). Due to this bad mixture, the pile was not getting hot enough and at the end there was far too much soil in the compost. It was good compost for seedling raising but too sandy for my garden (my garden is already too sandy). I then tried using food waste from a cafe but the food already smelt terrible before it even went in the pile. Although it got really hot it ended up as a sludgy stinking mess, not making me a very popular neighbour or husband.
Still, through all this experimentation I was able to monitor the results of the compost since I was using a lot of it for making seedlings to sell at market. Because seedlings are so small and the only soil they use is actually my compost I could monitor the success or lack of success from batch to batch. I found that the initial batches (from garden waste) were far better than the latter batches (of kitchen waste).
During my PDC we were taught how to make compost as well as how to make compost for compost tea. Our teacher, Paul Taylor, owns a company called “Trust Nature”. Paul advocated the use of weeds, grasses and thin woody material to make the heap. Importantly, he told us to add the roots of plants (for green things like grasses..maybe not tree stumps) as they contain a large amount of minerals and fungus.
Paul used a large amount of manure because it was fresh and available on the farm. I don’t like to buy manure from shops or landscape yards as most of it comes from factory farming operations. It’s also pasteurised/composted to such high temperatures that it kills most of the benefincial fungus and micro organisms. I just use manure from my chickens.
Here is my current recipe (I used a wheel barrow to measure but you can use anything handy):
3 parts brown (straw, paper, leaves, thin branches (like 2-5mm) etc.) and then 1 part green (grass, weeds, manure etc.).
Water every time you add the wheelbarrow load (or whatever you are using) until it is pretty wet.
Continue this procedure until you have approximately 1 cubic metre and make sure the last layer is a carbon (brown) layer. This helps keep off flies and vermin.
2. Treat your compost heap right!
Once you’ve built it, cover the pile with something like a tarp or plastic sheeting. This stops the pile from getting over-wet (from rain) but also keeps the heat and moisture in making it sweat.
I like to wait at least a week before turning the heap, but you could turn it as soon as the temperature starts to drop.Check it every day with a thermometer to see when the change happens. The cheapest option for a suitable thermometer is one used for testing milk (for making latte) and can be purchased from dollar shops relatively cheaply.
Providing you don’t you too much manure or food scraps in the mix the pile should only drop about 25% in size.
Turn the pile 6-12 times (the fewer turns, the longer you need to leave the pile between turns) watering it each turn to maintain a good moisture level. The way to check this is by squeezing a handful of compost. You should only just be able to squeeze a single drop of water from it. Any more and don’t water it.
Once the pile’s peak temperature stays below 40 degrees Celsius the thermophilic composting process (hot composting) has finished. The compost can be used at this time but there is still one more stage you can wait for if you choose.
After hot composting is over, compost moves into the mesophilic stage (cold composting) where the worms and other bugs move in. For me, the use of my compost bays is exclusively for hot composting. I make a lot of compost and I don’t have the room to mature the compost in the bays. I bag it up and store it under the house where it is cool. The worms and other bugs, surprisingly, have no problem finding their way it to the bags.
The pile has been ready for a few weeks now waiting for me to bag it up. When I was making the pile I threw in lots of sticks which I had not chopped up finely enough. I was aware at the time that these would not break down during the thermophilic composting process. It is something I do regularly and I don’t worry about it. I have to sieve the compost anyway to make it useable for my seedlings, so all the large pieces of wood get taken out. The wood is mostly broken down and brittle. I either use these twigs as fantastic mulch or I throw it back into a currently working (hot) compost pile where it will be totally consumed.
Although this compost it now ready to be used around the garden, it is always better to bag it and store it. Some people advocate storing compost for 2 years before using it, but I don’t have the space to afford storing 2 years’ worth of compost at a time.
3. Make sure it’s ready to use!
I suppose the first question should be “what difference does it make?”. If the compost looks soil-ish then it is probably more than ok to use on the garden. If the compost is not ready then the soil will act as a buffer until such a time it is ready for the plants to take it up.
Using unfinished compost as potting mix does not work. I lost several hundred dollars worth of seedlings last year due to compost that was not ready. I had made a batch of compost using mostly food waste and the seedlings looked bad. I was running short of time and had to hastily use a compost mix that I was not really happy with.
A couple of weeks later I listened to a podcast by Paul Wheaton (from the Richsoil.com and permies.com websites) talking with a lady called Helen Atthowe . Helen is a master gardener, farmer and all round soil genius. She was talking compost and described one of her earlier failures. She’d set up a tomato greenhouse and made large pots for the tomatoes using sacks of compost. A few weeks later, she came back and found all the plants dead. This was a commercial crop and the financial results were devastating. Helen explained that the compost was not finished, but did not go into too much detail about the how’s or why’s.
I remember immediately going to the greenhouse and looking at my plants and realising I had done exactly the same thing. Recently Helen gave another interview with Paul who asked for questions in advance. I wrote in and asked her to go into more detail about the issue. You can listen to the podcast here. My question starts at 12 minutes 15 seconds but the whole interview is great.
In simple terms this is how she explained how to see if compost is ready:
1. Do a PH test. If the test comes back with a high PH (like 9) it is not finished. If it somewhere near 6.5 it’s good to go.
2. Get a thermometer and check the temperature in the middle of the pile. Now check the temperature of ground soil next to the pile. They should be close in temperatures. If the pile is much warmer it is still composting and therefore not finished.
3. Know how to use your compost
I do not generally mix compost into the ground, but rather add it on the surface around new plantings and then re-cover with mulch. When I explain this technique to people they often find it quite strange and radical not to dig compost through your soil. That reaction doesn’t surprise me when virtually every gardening TV show and book tells you to “dig compost thoroughly through your soil to a depth of x cm”.
I have to quote Sepp Holzer here who, when asked questions on how solve various plant issues, regularly says, “You have to read from the book of nature”. I ask the question more literally as, “How would nature do it?”. When in nature, does freshly made compost (humus, leaf litter etc.) end up 30cm below the soil level? It doesn’t, does it? Leaves fall from the trees, grasses seed and die, animals poop and then die all- on the soil surface. That all slowly decomposes and earth worms come from below to eat the newly decomposed organic matter. Not only do they take the organic matter deep below the soil surface and excrete it as vermicast (worm poop); in the process they create tunnels in the soil, de-compacting the soil and allowing air and water deep down.
I have probably mentioned in other articles that digging, tilling or ploughing soil (irrespective of whether it’s a planting hole for a tree or an 10 acre field) immediately kills 30% of life in the soil (createing almost instant plant food which is why we think it to be so beneficial). Except, now instead of perhaps adding 10 kg of compost to that area, you now should add 13kg to make up for the loss created by digging. More work and more money spent for the same result. Doesn’t really make much sense, does it? However, if you are regularly top dressing soil with either mulch or compost (ideally both) your soil will be fully functional and powering out produce without needing to accelerate it by killing life. Lime also works by killing life, also giving the impression of being beneficial to the soil. If you need to raise the PH in your soil simply add compost! If you need to lower the PH in your soil simply add compost!
Compost is a great addition to your soil and is vital for making good seedlings. 1 cubic metre of compost (after being sieved) generally makes up enough potting mix (including all the other ingredients, but there is another whole article there) to make 10,000 seedlings using my 1.5″ soil blocker. That is more than enough for most serious gardeners for a year, so putting lots of effort in to making one really good pile each year is really worth it.
You could also save some of the compost to make a compost tea. 1 litre of your compost can be used in a tea to inoculate 1 hectare of land (10,000 m2), which is also another article in itself.
Making enough compost to regularly apply to your soil (as the books suggest) is another matter. I have never been able to do that (rather, I can’t justify the time and material required to make so much compost) so I now build my soil with limited compost and lots of mulch. Next article, I’ll tell you all about that and how to do it!
Meanwhile, have fun and happy composting!