Love your Blackland Soil

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I’m a dirt nerd. A soil snob. Don’t get me wrong, I appreciate a well-amended loam as much as anyone. But I’m from the Blackland, and it pains me when fellow gardeners roll their eyes in disdain of our beautiful dirt. Blackland soil is some of the richest on earth, and it’s also our unofficial state soil. Here are some reasons to show it some respect!

Of the 1300 named soils in Texas, the dominant soil of the Blackland Prairie is known as Houston Black (named for Sam Houston) and is exclusive to that area. Houston Black is recognized throughout the world as a classic example of a “vertisol”: black soil with a high percentage of clay called “smectite.” Smectite is what swells and shrinks and ruins our foundations; Houston Black is 60-80% clay. In dry times, vertisols form cracks up to 4” wide and 6’ deep. As Blackland kids, we’d run the hose into cracks hoping to fill them up. Never happened, but the cracks would break into heavy clods and become perfect grenades for
our battles (until somebody got hurt, which only took a minute).

Wet Blackland soil adheres to shoes in a grotesque sticky clump. In every rainy spell, countless flip flops vanish with an audible “Slurp!” into the morass. At my barn door there’s a 16” deep boot-sucking mudhole that appears after only three days of rain. Have you ever slipped on Blackland mud? It happens before you know it, doesn’t it? That’s due to another characteristic of Houston Black: it has “slickensides.” Formed by the soil’s movements, it’s shiny, waxy, and… slick.

Houston Black soil also features “hogwallows,” shallow saucers with slightly raised edges called microbasins and microknolls, usually spaced 6 to 12’ apart and 2-6″ deep. Only found in expansive soil, hogwallows were recently renamed “gilgai,” an Indigenous Australian term meaning “little water hole.” Seasonal gilgai enabled humans and animals to move about in previously dry areas.

In spite of Blackland soil’s bad habits, don’t forget how fertile it is! And it’s pretty when it’s not bending your shovel. I didn’t say “Love your dirt,” I said “Respect your dirt.”

For more info:
http://websoilsurvey.nrcs.usda.gov
https://casoilresource.lawr.ucdavis.edu/sde/?series=houston%20black#osd
https://soilseries.sc.egov.usda.gov/OSD_Docs/H/HOUSTON_BLACK.html
https://www.nrcs.usda.gov › stelprdb1237001.pdf

For good soil texture for plant growth, 50% of the bulk of soil is weathered geologic material, i.e. minerals plus organic matter (decaying plants and animals). This is usually about 45% mineral and 5% organic. The other 50% should be half air and half water. To amend clay soil we can use expanded shale, rock heated to high temperatures that make it porous or organic matter. Composted organic matter is best since the process of decay uses up nutrients plants need. Clay soil amended with compost has speedier drainage and more air pockets.

Article By: Dollie Love, MG Intern

 

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