Go Eat Dirt, Nerd.
From the same garden advisor who brought you Dirt Nerd, welcome to a new column that is exactly like the old column but with a different name. Neither of these columns have explicitly focused on dirt or soil but, as this is the medium through which plants historically and prehistorically have grown in, both feel like fitting and adjacent primary noms de plume. I plan to continue being nerdy and educational, and as such, a transition from “nerd” to “ed” feels sensible as well. Nothing has changed and everything is different. In some future column we’ll surely address the reasons for the name change (spoiler: It wasn’t exactly my choice, barely a choice at all, really). But this month, as an homage to the nomenclature, let’s dig moderately deep into dirt and soil and mediums that aren’t exactly either, and what to use for what and where when gardening.
I’ve definitely written about mulch in the past, and lead poisoning, and raised beds, and the best soil for potted plants, and probably have addressed dirt in innumerable other ways through the years, but never has it all been in one place all at once for you to consider as a unified whole.
Let’s begin by differentiating dirt from soil. Informally, the term “dirt” is used interchangeably with “soil” all the time, by me and you and everyone we know, even by corporate agro bigwigs such as Miracle-Gro.
However, by definition dirt cannot support plant life. It is nothing more than a lifeless ground up combination of silt, sand, and clay, lacking in organic matter with little or no capacity to retain liquid or air, and without any living matter within it (though it still does have a mineral content as it is pretty much just tiny ground up rocks).
Soil, on the other hand, contains dirt and so much more. Soil is an ecosystem in its own right, one that supports multiple life systems, helps facilitate the exchange and retention of nutrients, works actively within the carbon cycle, retains oxygen and water, and helps make life on this planet possible.
Turning dirt into soil takes millenia, and we have been scraping off topsoil made of organic matter and turning verdant landscapes and farmlands into erosive dustbowls at a disastrous pace for a few thousand years now. This is a problem that cannot be fixed easily. On a local scale, however, you can totally turn dirt into soil with the use of compost. Because, at the end of the day, it really just takes organic matter (i.e., life) to bring life to your soil. A little bit of compost brings fungi and worms and all sorts of microscopic organisms together to bring all that aeration and water retention into a world where plants can grow.
We might as well get into compost while we’re here. It is not dirt or soil. But, like dirt, it is a necessary component to making soil. More importantly for the home gardener, it’s a fantastic addition that helps to continue to enrich soil through the ages, and it’s never ever a bad idea to use it in any garden as frequently as possible. However, while it is totally feasible to grow plants in pure compost, it is generally not a great idea. Without a dirt or soil base, compost can often be far too dense to let roots breathe properly, and if it is too high in nitrogen it can also burn your plants. Ironically, compost is a great addition to soil to help make it less dense and more porous, and you absolutely want nitrogen added to your garden beds. All things in moderation.
When it comes to what kind of soil you want in your garden, it very much depends on what kind of garden you’ve got going on—the most important factors here are density and access to broader ecosystems. Basically, smaller spaces (like container gardens) need the fluffiest, most porous and nutritious potting soil you can afford, whereas larger spaces (like row cropping out of the ground) will work just fine with some bulk topsoil and regular additions of compost and mulch. It follows that situations closer to the middle (like raised beds) need porous, light, nutritious soil, but this can be accomplished with a winning combination of topsoil, compost, and coir, peat, or something of the like that facilitates air flow and water retention.
Regularly adding mulch to a garden bed of any scale can feel a bit luxurious, but the benefits are extremely worth it in a few ways, especially in the context of building healthy soil. Mulch retains moisture and helps invite and introduce the soil microbiome you want to see in your little world. It also breaks down with time, adding fresh compost to your soil and helping to develop its health and growth over the long term.
Just as the texture and quality of your soil needs differ depending on what and where you’re growing, the type of mulch you use is also extremely important. Mulch is generally very carbon-rich and needs nitrogen to break it down into organic matter. Unfortunately your plants also need nitrogen to grow and thrive. As such, using a heavily carbon-based mulch such as wood chips, shredded wood, or cardboard to mulch can severely inhibit the growth of plants, especially young or annual plants. Compostable pots are also a terrible idea for this reason. For plant growth, plastics rule, carbon drools. Sorry. Woody mediums also encourage fungal growth over other sorts of positive ecosystematic growth, which is great for larger plants like shrubs or trees, but not great for herbs or vegetables. Lean towards leaf matter and pine straw for your babier babies.
I hope this was a winning introduction to Soil Ed for the lot of you nerds. Stay dirty.
illustrations by Rachel Speck
