How To Manage a Compost Pile Using Temperature

compost temperature chart

I’ve always been confused about when to turn a compost pile. Some people suggest lots of turning while others don’t turn at all. I built a pile in December using a technique I learned from Will Bakx, soil scientist and operations manager of Sonoma Compost. Bakx recommends keeping the pile between 131° F (55° C) and 163°F (72°C) for a period of 15 days. The only time you turn is when the pile starts to dip below 131° F or to prevent the pile from going above 163°F.

The technique is simple–all you do is take the temperature once a day with a compost thermometer and write down the result on a calendar. The graph above is the result that I got from a pile made out of horse bedding, chicken manure from our hens, plant materials, straw and brew waste from a local brewery.

The red area on the chart is the thermophilic temperature range (135° -160° Fahrenheit). The dip you see at day 15 is the one time I turned the pile so that I could keep it in the thermophilic range. Using temperature as a clue to when to turn the pile has a number of advantages:

  • You can make sure that the pile does not get too hot. Above 160° F  you start to kill off the thermophilic bacteria that decompose your pile. To decrease temperature you turn and add more carbon material and water.
  • Washington State University recommends subjecting all of the pile to temperatures above 150° F to kill potential pathogens. I’m fairly certain that, with the turn I did at day 14, all of the pile got up to 150°F.
  • Weed seeds are killed above 130°F–another reason to watch temperature.
  • Failing to get high temperatures can be an indication of too much carbon or a lack of water. To correct, add more nitrogen and water and turn.
  • A loss of temperature could indicate that the pile is going anaerobic. The solution is to add more carbon material and turn.

Once the pile has had 15 complete days over 131° F you just let it sit. Compost is done when it is dark, smells like earth and you can’t recognize the original ingredients. It will likely be several months before it’s ready to use. I’ve found that I need to turn the pile periodically and add water after the initial thermophilic period due to our dry climate.

The mass of the pile is a factor as well–I’ve found that it needs to be a minimum of one cubic yard of material to start with. So I save and scavenge materials that I can use to build a pile all at once. The small trickle of kitchen scraps we generate each day goes into our worm bin.

Despite the geekery with using a compost thermometer, I’ve found that this method saves labor. Back breaking turning only happens when it’s necessary.

Tracking the Mood of the Gardener

Swiss chard--January 2010

Swiss chard from the winter of 2010

A Root Simple reader I ran into this weekend took issue with my assertion that fall is the best time to start a vegetable garden in Southern California.

Thinking about it some more I think she may have a point. Some of you may have noticed that we have a new feature on the blog–if you click on an individual blog post you’ll see a list of related posts at the bottom. Looking at some of those older posts showed that I have an annual vegetable gardening freakout around November. Why? Two factors: freak heatwaves (that are common here in the fall) as well as skunk activity which is related to applying compost (they are digging for grubs). So it may be, in fact, better for us to delay planting by two months, at least in our central Los Angeles microclimate.

The moral of the story is that it’s valuable to keep records for your vegetable garden, specifically:

  • Planting
  • First and last harvest
  • General observations–taste, flavor etc.
  • Mood!

Gardening and human consciousness are very much intertwined. Our thoughts effect what happens in the physical world and vegetables are heavily dependent on our interventions. Looking back at old blog posts as well as reader comments have led to many insights. If you don’t already, keep a gardening diary.

So what kind of records do you keep?

Anne Hars’ Top Ramen Keyhole Vegetable Garden

keyholewide

“I call it my Top Ramen garden,” says gardener, Root Simple neighbor and artist Anne Hars, “I planted things that go well in Top Ramen.” Hars is referring to her keyhole vegetable bed that she created this winter. With the keyhole, Hars has made good use of a very small front yard with a dense planting of Ramen friendly veggies including bok choi, three kinds of kale, sunflowers, carrots, peas, garlic, radishes, spinach, romaine lettuce, cilantro and parsley.

keyholeanneanebill

Anne with husband Bill and Petra the chihuahua.

She was inspired by a video by the British charity Send a Cow that shows the construction of a keyhole bed in Uganda. Keyhole beds are raised, circular vegetable gardens that contain a compost pile in the center. The compost pile provides nutrients and worm habitat. The keyhole form is said by permaulturalists to maximize space and ease of access.

Hars’ keyhole bed replaced two square raised beds that were made out of wood. “Gardens have to be rethought every couple of years and I feel less guilty then I did when I was using wood,” says Hars referring to the straw wattle she used to edge the keyhole. Straw wattle is a (mostly) biodegradable material made out of rice straw and plastic netting. You can find it at irrigation supply stores and on order at Home Depot. It comes in 25 foot lengths.

Soil for the bed came from the ground, from bagged soil that used to be in the wooden raised beds and from compost that Anne makes herself.

keyholeuta

“I’m going to plant things under things,” says Hars. As the winter garden reaches maturity Hars plans on putting warm season crops in under the winter greens. “It will be a lazy summer garden.”

Ute, one Anne and Bill’s two chihuahuas, agrees.

An Aquaponic System in Oakland

Root Simple pal Federico alerted me to an interesting aquaponics project in Oakland, CA created by Eric Maundu. I share with Federico some skepticism when it comes to aquaponics–the concept seems a bit complicated and plastic intensive to me. But Federico thought, and I agree that this project might be simple enough to be practical.

If any of you have experience with aquaponics, let us know what you think.