Confessions of timid gardener, part 2: what does ‘soil health’ mean anyway?

To read part 1, click here.

As I’ve been browsing different websites and resources about planning and designing my native plant garden this spring, I’ve kept coming back to something – I don’t know much about the soil in my garden. So while sure, I’m excited to plan the garden and look forward to getting new plants, it seems prudent to spend a little bit of time assessing and improving the condition of the environment that hopefully will sustain those new plants (aka, let’s not spend good $$ on something and then not set the stage for it to succeed).

Our house was built in the last ten years, and the garden bed that I’ve designated for my native plant experiment was dug only three years ago when we installed our deck and patio. I know from the deck construction that the in-situ soil is quite sandy with a lot of cobbles in it (evidenced by the much colorful language voiced from my husband and his helpers when digging the holes for the deck foundation). In making the garden beds, I know fill was brought in and mixed with the soil after we removed portions of the lawn. And I know I’ve added some bags of compost since then and we have a layer of mulch on top.

That is the extent of my knowledge about the dirt in my garden. Is it good soil? Is it ‘healthy?’ I don’t really have a great gauge on that – the existing plants seem to be doing ok, but they also haven’t gotten much bigger in the three seasons since they were planted.

It’s time to learn more. Let’s dig deeper! (ha – sorry, couldn’t help it.)

The target garden bed for my native plant journey. This picture was taken approximately 2 hours after the landscape workers left in 2019. Hostas, daylilies, and some spreading geraniums are what we have in the ground.

The University of Minnesota’s Department of Soil, Water, and Climate hosts a Soil Testing Laboratory, and for $17, they are willing to take a sample of submitted soil and tell you all about the soil texture, soil pH, its organic content, and levels of key nutrients like phosphorus and potassium. Your results then will also include some recommendations for improving the soil based on what type of garden you’re trying to build (flower vs. food vs. tree/shrub vs. lawn). Turn around time for the analysis is about 2 weeks.

Sounds like a good place to start.

So this past weekend I got out my gardening gloves, a bucket, a trowel, a quart sized ziploc, and some printed sample collection instructions from the UMN Soil Testing Lab. I waited for a moment where the sun crept out for twenty minutes between the rain/slush/snow storm stuff that is Minnesota in April, and started digging some holes in the ground.

It took me about 10 minutes from start to finish to collect the sample. I dug and combined soil from four different holes in my target garden.

Collecting the sample is quick and easy. You want a representative sample across the garden of interest, so it is important to collect soil from a few different spots and mix it together. To dig a hole, you remove the surface material (mulch/plant debris) and then go down about 6 inches (the UMN info sheet gives guidance on hole depth depending on your intended garden type). Take a few scoops from each hole you dig and put them in your bucket. Once you’re done digging, you mix the soil in your bucket so its solidly combined and place about 2-4 scoops (2-3 cups) in your ziploc bag or container. Make sure you label your sample and fill out your paperwork. Your soil is ready for submission either by mail or dropoff at the soil lab.

I am curious to see my results and I am also intrigued to learn what I can do to improve the soil. As I’ve worked more with gardening-inclined folks and farmers this past year, I’ve heard the phrase ‘soil health’ a lot, and I feel it’s one of those terms that people throw out there and we all have a different picture of what it actually means. Does it refer to how well plants grow in the soil? Is it a texture or a water retention related metric? pH? Balancing nutrients? A combination of all these things?

What’s become clear in my conversations with folks is that soil health is less about the physical dirt and more about building and maintaining a diverse soil ecosystem. Yes, soil is composed of inorganic content like weathered rock material, minerals, air, and water, but it also has living and decomposing organic components. In just digging my four quick holes to collect my sample, I encountered plant roots and disintegrated leaves and decaying mulch. I even turned up a couple earthworms (which by the by, are totally invasive). And this environment of inorganic and organic materials is what sets the stage for microbial activity that transforms soil into a truly magical substance capable of feeding plants, retaining water, filtering pollutants, cycling nutrients, and providing a solid medium for plant roots and our infrastructure.

A handful of soil has more microbes (e.g. bacteria, fungi, etc) than there are people on Earth. And those microbes do a LOT of really important work. Microbes take nutrients and process them so they then are available to the plants. They help protect plants from diseases and pests. They break down organic material that improves soil structure and can even sequester carbon. It is these microbial populations that really help determine your soil’s health and subsequently, the health of your plants.

Seeing my soil as a living entity – a ecosystem of interactions and feedbacks of billions of microorganisms with their surrounding environment – suddenly makes it that much more interesting to me. My garden is an integrated system versus just inputs of various things. It gives me my ‘why’ when I think about what I can do to improve my soil – let’s support those microbes!

Hopefully the results from my soil test will provide some good guidelines on how to do just that.