By Mollie Henry

As urban gardeners, strong soil health is a major factor in the health and vitality of our plants. Through mulching, crop rotation, cover crops and other best practices, we can protect soil from nutrient depletion and erosion. However, even these practices can sometimes fall short, and many gardeners turn to buying commercial fertilizers and store-bought soil with unknown origin.

But there’s a better way! By composting kitchen waste and leaves, you can “grow” your own soil, which saves money, provides better nutrients for your beds and cuts down on your household garbage and yard waste.

Kitchen waste – also known as “greens,” provide the critical nutrients of nitrogen, phosphorous and potassium that plants need for root, flower and fruit development. Dead leaves – also known as “browns,” provide carbon, the main fuel source for plants. Trees capture solar energy in their leaves, store it as carbon, use that carbon as fuel to grow, and when they drop their leaves in the fall, much of that carbon remains in those leaves that can feed the microbial workforce that turns compost into humus and continues to make soil good for plants. Humus provides structure and a continued source of carbon for our homemade soil. 

Composting is the way we make soil and is essentially mixing kitchen waste and leaves (or other dead plant matter) at a ratio of 1:3 and letting the mixture decompose. The rate of decomposition will vary, and you can accelerate the rate by chopping (mowing) your leaves before adding them to your compost, making sure your compost pile is large enough to retain heat (or is in a container that you can expose to sunlight), mixing the compost every week and keeping it moist (this isn’t very difficult, because kitchen waste generally contains a lot of water – but if your compost ever appears dry, it’s OK to water it). In my yard, I can convert a load of compost into a rich, dark amendment in about six months, which is why I have four separate compost containers in production all at once, at various stages. They give me about three one-gallon buckets of fertile, energy-rich, organic soil every quarter that I use for side-dressing or working into new beds. 

The fall season is a great time to start your soil farming career – in fact, soil farmers call this the annual “gold rush,” because free carbon is everywhere in places with deciduous trees. Many people have climbed aboard the “leave the leaves” campaign to support their yard’s insect ecosystem, which needs leaf cover for overwintering – and that’s a worthy endeavor. If you’re on that team but still want to grow your own soil, leave your own leaves and help yourself to your neighbors’ bags of leaves that will inevitably appear on curbs throughout Nashville. Pro tip: Bags in paper (rather than plastic) are easier to manage and save. Four or five leaf bags can be enough to feed your soil farm for an entire year!