Unfortunately, in many urban environments the native soil was severely damaged during development – stripped of topsoil and organic matter, compacted so it doesn’t drain, and left containing construction debris.
In this section we will explore the basics of building healthy soil, addressing compaction, organic matter, permeability, water retention, nutrients, and microbes. Below are some starting tips. Also see the Resources Area for some good references while additional content is being prepared.
It helps to understand what lies hidden beneath the sod in your yard. Typical development practices destroy the health of native soil – just look at these photos from a typical suburban development.
So, before you spend a lot of money on plants, build healthy soil first. Start with these steps:
1. When planting new garden beds, trees, or shrubs, over-dig the bed and break up compacted soil. Break the soil into clods clumps the size of golf balls or tennis balls. You don’t have to till the soil into fine particles, but you do need to create fractures in the soil that will allow plant roots to grow downward.
2. Add organic matter. Mix it into the soil to keep the clods from compacting back together. This is especially important if you have clay soils. I prefer compost over peat moss because it is a renewable product and provides beneficial microorganisms (see suggestion 4).3. If you have clay soil you may be tempted to add sand to your soil to loosen it up but you will need to add a lot (probably 50% of the mix) to keep the clay from smearing back together. If find that organic matter does a better job of improving the soil.
4. Add beneficial microorganisms to your soil. Fungi, bacteria, and other microbes in the soil are typically unseen but are hugely important. The photo below shows a handful of soil from the forest floor by my house. The white threads in the soil are fungal mycelia. The mushrooms you see in the forest are just the fruiting bodies of fungi; most of their growth is below the soil and the fungal threads that grow through the soil form intimate networks with plant roots making minerals and water more available to plants. Bacteria and other organisms also provide similar benefits. Compost is a good starting point to add microbes to your garden soil, or try applying compost tea. Suppliers of compost tea are becoming more common as the benefits are becoming better known.5. Once you get your garden bed soil improved and your garden established, whether flower or vegetable garden, try to avoid tilling the soil. Tilling harms the microorganisms in the soil; it breaks apart fungi, exposes the soil to sun and light, and oxidizes the organic matter and microorganisms. Try to stick to no till as best you can.
6. If you have a lawn that is highly compacted with poor soil underneath, it would be a lot of work to rip it out, improve the soil, and replant. So work to restore it a little each year over time. Try core aerating your lawn each fall and top dress with compost. Over time that will work organic matter into the upper portion of the soil.
7. Go organic. Avoid pesticides and use organic fertilizers. Chemical fertilizers are harsh on the soil and the microorganisms within it. Overuse of pesticides harms pollinators and other beneficial insects whose populations are already in serious decline across the globe.
8. Get a soil test before amending your garden beds or lawn. They are low cost or free through university extension offices in many states. The fertilizer recommendations that come back with most tests assume you will use chemical fertilizer, so talk to your county extension agent when you get the results back and ask them to provide recommendations for organic alternatives. The books in the Resources section are also good references on understanding soil nutrient test results.