Compost has been on my mind recently- I just completed a new compost bin and reorganized our composting station. Based on some questions I've gotten, it sounds like there is interest and that people have basic questions about home composting. So, in the spirit of International Compost Awareness Week, my wife and I decided to co-author a post to get the word out and hopefully to inspire some intrepid composters out there to get after it.
Composting is a very simple process that people have been using in their gardens since, well, since people started to have gardens. But, unfortunately, if you read articles online about composting, it is easy to get overwhelmed and discouraged by all the information about the do's and don'ts.
Soil does not only come from a bag at the home center. Like many things, it all begins at home.
Composting plays a big role in our garden, our home and our landscape's sustainability. Apart from diverting waste to the landfill, composting kitchen scraps, yard waste and vegetable garden waste is a critical component of maintaining nutrients and resources locally; very locally- within our own yard. By composting plants and leaves, you are taking the nutrients you have given them and put them back into use.
Composting can save a lot of money- you have the ability to make your own garden soil, and it is really a very simple process.
Compost is a great additive for soil structure problems. For example if you have clay soils, adding compost will help make it less clay-ey and better drained. Likewise, if your soil is rocky and too well-drained, compost will help you to retain soil moisture. It is the truly magic fix all. Sort of.
HOW to compost.
Unfortunately, the mystery and details that surround composting keep people from doing it. You can read up on all the minutiae about C:N ratios, proper temperatures for optimum composting, worm composting, compost bin types, compost accelerators, etc... and it is easy to get overwhelmed. In its simplest form, it is just a pile that allows air, water, bacteria, microorganisms, and invertebrates (worms, insects, etc...) to feed on and interact with food and yard waste to break it down and turn it into soil. It goes on everywhere in the world- with or without people maintaining it.
Keep it simple and just do it. You don't even need a fancy bin. A pile will work just fine. Forget temperatures and ratios.
1. Keep it turned. This is just literally turning the pile over with a shovel or pitchfork a little at a time on a regular basis. Turning it exposes it to oxygen so the microbes and insects can stay alive and do their important work.
2. Keep it moist. Some parts of the year in Missoula you have to water it like it was a plant or a pet. It is a living thing after all. We have a micro-emitter in our compost that is in-line with our vegetable garden, so it gets watered automatically during the warm months (June-September).
3. Keep it warm. Put your compost heap in a south facing location. A well-tended compost pile will generate its own heat and won't even freeze during the winter. Even dedicated compost tenders sometimes struggle with the temperature in Missoula, so help yourself out and put it in the sun.
What goes into the compost? Everything expect meat (fish and fish parts are fantastic, though) and oils. Paper, kitchen scraps, coffee grounds and even filters, vegetable garden scraps, yard waste, leaves, cut grass (unless it has been sprayed with herbicides), yard cuttings (unless they have been sprayed with herbicides) etc... Another thing we are careful of are weed seeds and rhizomatous grasses- our compost might not get hot enough or stay hot enough to kill these, so typically we send those to the landfill.
What about manure? Although manure is really helpful for your garden and compost pile, be careful of adding animal manure to your compost, because if the source animal ate anything that had been sprayed with an herbicide, the herbicide has most likely traveled through that animal and come out in the manure. This is surprisingly common. We recently learned the very sensible trick of doing a quick test on manure: all you have to do is plant some bean seeds in a sample of that manure. If it has herbicides in it, the bean will sprout and then get very sick or die. If the bean is fine, then the manure is fine and you can compost it.
Does compost smell? Not if you're doing it right. If it does smell bad, then something is wrong; most often the compost pile needs to be turned so it can get more oxygen.
How do you know when it's done? At some point, you will have a big heap of "stuff", some of which is compost and some of which is still decomposing scraps- not everything breaks down at the same rate. This is where the screening process comes in. Shovel your mix onto a screen of some sort, shake it, and the "finished" part will separate from the "unfinished" part (here is a link to a post showing the sifting or screening process).
Below is a picture of the compost that has been screened and is now ready to put on the garden.
You can also test the nutrient richness and composition of your compost with a soil test kit (we love ours, see below). We test our vegetable garden soil to evaluate its pH, and the relative quantities of N, P, and K and it is a lot of fun. It takes the mystery and guesswork out of diagnosing plant and soil issues. For example, most of our raised beds suffer from a lack of N.
So, it is easy to think that the compost is nitrogen poor, too. We don't routinely add manure to our compost (too afraid of pesticides in the sources), but we do add fish waste (entrails, etc...), which is a fantastic source of N. When I tested freshly sifted compost yesterday, I was surprised to find that the fresh compost is actually very high in N and P.
So if our compost is rich in N, and we add it to the garden beds, why are the garden beds still low in N? They are a couple of things at play. One is that the compost is initially high in N and P, but as it gets watered (and plants grow in it), the nutrients leach out (or get taken up by the plants). Since we don't know what type of N (and its availability to plants), it could be that it is all getting used quickly. So we also add blood meal to the raised beds during the growing season.
Another important tool for the garden (not just compost testing) is good record keeping.
So, from your friends at Montana Wildlife Gardener, we wish you a joyous International Compost Awareness Week!