The problem with soil is that most of it is underground. How are we supposed to learn about it or see how it’s doing? Last year, I polled a group of soil experts and wrote a post on what we actually know about how various prairie management techniques affect soil carbon. It ended up just being a list of all the things we don’t understand yet. It was disappointing, but not really surprising. Soils keep their secrets buried.
When I was growing up, my dad worked as a soil scientist. For many years, his primary job was to create soil maps – in part to help farmers, ranchers developers, and others understand what they could expect from or do with any particular piece of land. As I understand it, Dad and others used aerial photos and other clues to find where breaks in soil patterns might occur and then went out and poked a bunch of holes in the ground. They’d pull up a skinny sample of the soil, look at the color, texture, and other features, note the location, and then repeat that process many thousands of times. That’s a really difficult way to make a map.
I did learn one interesting thing from my father the soil scientist though, and it has stuck with me to this day. Maybe it’ll be helpful to you too. You’ve probably wondered about the difference between ‘soil’ and ‘dirt’. Well, the mantra I was taught is this: “Dirt is in your fingernails. Soil is in the ground”. There, doesn’t that make you feel smart?
This doesn’t necessarily count as an interesting thing, but I also know that the state soil of Nebraska is Holdrege Silt Loam. You’re probably thinking, “Wow, how does he know the state soil off the top of his head??” If you’d grown up in our family, you’d remember it too because Dad asked that question to nearly every person he struck up a conversation with – wait staff at restaurants, people sitting next to him at social gatherings, and anyone else within earshot. It wasn’t embarrassing at all.
Regardless of my soil-related childhood trauma, the more I learn about prairies, the more I appreciate how important enthralling and soil really is. Microbial communities in soil, for example, play immensely important roles in prairie ecosystems. At least, that’s what I’m told by people trying to study them. Imagine having that job, by the way! “Here, figure out what these millions of different microscopic creatures are and what they do. Oh, did I mention they all live underground? Ok, bye!” Studying zooplankton in the ocean is probably really challenging too, but at least you can swim down into the water and look for them.
I’ve tried to understand the relationship between soil and plant roots, which has been really fascinating, if confusing. Prairie plants are well known for their deep roots, though as I wrote about in another post last year, they don’t seem to use them they we assumed they did. Regardless, plants extract nutrients and water from soils – with a lot of help from microbes. They also need soil as a place for seed germination, a medium in which to anchor themselves, a place to hide their nutritious tubers and other carbohydrate stores from hungry aboveground creatures, and much more.
Most of you know that I spend a lot of time trying to learn about insects and other invertebrates, especially by finding and photographing species I don’t recognize and then trying to identify them later. I recognize I’ll never come close to photographing the incredible diversity of prairie insects, and that’s just counting the ones living aboveground. The biomass of invertebrates is 10 times higher underground! That’s intriguing and impressive, but also kind of depressing. How am I supposed to photograph insects down there?? First of all, it’s dark. Second of all… I mean… there are so many second-of-all obstacles, I don’t even know where to start.
Despite all the challenges of understanding soils, I do know a little about them, especially when I can watch the impact of soil qualities on aboveground vegetation. Our Platte River Prairies, for example, grow mostly in alluvial (water-formed) soils. At one point or another, river channels flowed through the current location of today’s prairies, depositing sand, silt, and other dirt-related particles (sorry for the jargon) in meandering stripes across the landscape. From the air, you can clearly see the layout of those soil lenses, even in tilled land. The patterns become much more pronounced during spells of dry weather because plants growing in lenses of soil with less organic matter wilt and turn brown much faster than those with more organic matter.
Even during periods of abundant rainfall, a discerning naturalist can identify where drought-tolerant and drought-intolerant plants are growing and make deductions about relative soil organic matter quantities accordingly. It’s fascinating to watch new plant communities establish when we restore crop fields back to prairie vegetation. We spread seeds of 150-200 plant species across those fields and then wait to see what species will grow where. With good and timely rains, just about any seed can germinate and start to grow anywhere in that field. But once we hit the first drought period, local neighborhoods start to form based on whether they are well adapted to the soil characteristics below them. I always figure a new restored prairie isn’t a mature plant community until it’s been through a couple extended drought periods because that’s when the sorting happens.
I can also see the effects of soil characteristics at our family prairie, as well as at the Platte River Prairies, when I look at differences between plowed and restored prairie and unplowed remnant prairie. Again, in years with consistent rainfall, the productivity can be similar, but any short spell without precipitation produces sharp contrasts. On any site with a history of cultivation, the grasses are less dense, shorter in stature, and quick to turn brown in the absence of consistent rainfall.
Sometimes, you can even see distinctions between formerly plowed and unplowed prairies within the same day. On a hot dry day, even if we’ve had recent rains, the baking heat of the afternoon sun can start to wilt plants, and that wilting tends to be much more pronounced in soils that have been farmed. That’s true even at our family prairie, where former farmland was put to grass way back in 1962. Those soils are still far from regaining their former productivity.
Unless someone invents snorkeling gear for soil exploration (imagine the marketing campaign!), I’ll probably always have a fairly surface-level understanding (so to speak) of prairie soils. I try to stay abreast of what experts are learning, but I frankly have a hard enough time keeping up with what’s happening aboveground without also trying to pay attention to subterranean goings on. I’m hoping my friends who do the hard work of studying soils will just tell me when there’s something I really need to know. In the meantime, I can always fall back on the knowledge I gained when I was a kid:
“Dirt is in your fingernails. Soil is in the ground.”