Soil Facts: Basic Information on Soil You Need to Know

The soil is perhaps the most overlooked, underrated, taken for granted but major partner in growing. When plotting gardens, how many have passed over getting to know their soil—reading up on soil facts—in favor of planning the layout of their gardens? How many have agonized over which plant goes with what month, foregoing reading on soil information about their area first?

Admittedly, there’s hydroponics, a good alternative to growing without soil. But it’s a specialized field, requires specialized equipment and regular monitoring of inputs, temperature and other key data. For most, soil is still the preferred method for planting vegetables and growing trees.

Soil is a non-renewable resource—at least, that part of the soil fit for planting. And soil doesn’t appear by magic. No wand-waving fairy chanted some abracadabra in the night to create soil. It’s a slow process.

To better understand soil, let’s brush up on some facts about good ol’ soil before we start digging up some dirt.

What Soil is Made Of

So, what is soil? The USDA has this to say:

Soil is a natural body comprised of solids (minerals and organic matter), liquid, and gases that occurs on the land surface, occupies space, and is characterized by one or both of the following: horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural environment.

Lengthy definition, that. But reading closely, soil has many things in it: nutrients; minerals; dead, decayed stuff; water and other liquids; and air and other gases.

And–surprise?–soil has horizons just like the atmosphere and each is easily identifiable from the other.

Soil Composition

So, soil is a mishmash of many things from all over the place—small pieces of broken rock, fallen leaves, dead critters, decomposed tree branches, and of course, decayed plants, to name a few.

And because of the different materials and processes that affect its formation, soil comes in different colors and textures. Soil could have such lively colors as red, yellow and white but most of the time, soil is black, brown or gray. Due to the sand, silt, clay and other mineral particles in it, soil could be smooth, creamy, rough, crumbly and sticky to the touch.

Did you know that soil stores 0.01% of the total water on Earth within its pores, nooks and crannies? To be exact, a typical healthy soil sample contains the following:

• 45% minerals
• 25% water
• 25% air
• 5% organic matter

Did you know, though, that an acre of soil can hold about 5-10 tons of living beings? Our intrepid soil scientists give us this mind-blowing fact: one measly gram of soil could hold as much as 5,000-7,000 bacteria species.

The soil you’re walking on is teeming with gazillions of tiny, unseen critters—and you don’t even realize it. Imagine that!

Soil Formation

Soil takes its sweet time forming. Left to its own devices—which is the only way, too—soil can take about 500 years to create just an inch of topsoil.

Natural processes like weathering, erosions, rains, floods, hurricanes, thunderstorms, tornadoes and the like all contribute to soil formation. Lichen and plant roots also help break down rocks into little pieces to become part of the new soil.

Another amazing fact: five heavy tons of topsoil, if you spread it across an acre of land, is only as thick as a dime. Bet you didn’t know that!

Soil Layers

Like the atmosphere, soil also has layers called horizons. Four, to be exact. And they’re called, by unexciting but unforgettable names: Horizon O, Horizon A, Horizon B and Horizon C.

Horizon O is the topsoil that we walk on. It’s one-inch thick and made up of decayed, organic stuff that feeds the soil and keeps it healthy. Horizon O is the most fertile, productive layer because it contains yummy humus and busy microorganisms that make nutrients available to plants.

Horizon A is the layer after Horizon O. It’s also part of the topsoil, composed of roots and beneficial microorganisms like mycorrhizae and fungi that feed on the waste materials shed off by roots. Of course, this horizon is also home to those wonderful critters that gardeners love—like earthworms and centipedes.

Horizon B, the layer that follows, is a very tough layer. The soil is so hard that no root or critter can penetrate this barrier.

Immediately after that is Horizon C, the parent material—rocks and old soil that form all the horizons above it. This layer contains primary bedrock, secondary materials from other places, old soil formations and the like.

As you can see, the soil beneath your feet is a hectic world swarming with life!

Next time, we’re going to discuss the five different types of soil…and which is best for gardening and growing particular plants.

In the meantime, after it has rained, go out with your handy trowel and start digging in your backyard. Check what you see and share it here in the comments section.