Organic Gardening: Fall right for compost

While many people associate autumn with a kind of death and a return to school, ugh, gardeners know that this is the season of bounty. There’s a reason that Thanksgiving happens in fall as it coincides with the harvesting of crops and the culling of animals. But along with the harvest comes a surplus of dead plant material including leaves, spoiled produce, spent plants and the bales of decorative straw that the neighbors bought for Halloween. This secondary harvest can form the beginnings of a compost pile.

Gardeners use compost as an extremely slow-release fertilizer, but also for its ability to buffer pH and soil moisture and as food for the billions of micro-organisms that inhabit every square inch of healthy soil. Compost itself is living stuff, containing multitudes of beneficial fungi, bacteria and other microbes. Although it contains nutrients, compost makes these available slowly by feeding the micro-organisms that in turn feed the plants. Contrast this with water-soluble fertilizers that feed plants directly and then sink out of the system before needing to be re-applied. Compost often only needs to be added once a year.

As mentioned above, compost acts as a sponge, holding onto excess moisture to keep the garden moist, but not wet. It also improves the physical properties of soil by adding and feeding microbes which emit exudates – also known as “goo” – that bind soil particles together. This process encourages aggregation – the formation of loose or hard soil into crumb-like particles–that allows a gardener to more easily work the soil while also providing pathways for water and roots. It’s no wonder that a seasoned organic gardener’s suggestion for improving soil often amounts to two words: “add compost.”

Fall supplies a bounty of both “green” and “brown” materials for starting a compost pile. The “green” materials are high in nitrogen and would include things like spoiled produce, grass clipping, recently dead plants and manure. “Brown” materials are high in carbon and include leaves and straw.

If you have a lot of both materials, you can make a large pile all at once by layering your greens and browns at 8 inches deep or so and capping off the pile with a layer of brown material to suppress any sort of smell. This creates the right chemical balance of nitrogen and carbon and also allows air to penetrate the pile through the relatively fluffier layers of brown material.

When building such a pile it’s good to water constantly with a hand-sprayer, wetting down every layer as you build it. Water as well as food – in the form of green and brown material – and air are the three primary things you need to keep the composting microbes going. Many composters will also add some amount of finished compost or rich topsoil to their piles to inoculate the heap with micro-organisms, although such microbes will always find a way in one way or another.

If your pile is big enough–say 4 feet wide, deep and tall – it should heat up quickly and then cool down after a few weeks. As it starts to cool down, turn the pile using a pitchfork moving the outside materials to the inside and wetting it as you go. This restores moisture and air to the pile and expedites the composting process. You can do this several times in the life of a compost pile.

Those with smaller amounts of compostable materials may want to take a “build-it-as-you-go” approach. In this case, stockpile brown materials and add them after every addition of green kitchen or yard waste, slowly creating a pile like the one mentioned above. This pile may not ever fully heat up, but it will break down in time and keep materials out of the landfill.

Once you start composting, you are unlikely to ever look at your neighbor’s bags of dead leaves the same again. They certainly won’t miss them.

Brian Allnut is a freelance writer and organic gardener in Metro Detroit. You can reach him at detroitfarmandgarden@gmail.com.