Soil School: Reading the layers of a field's soil profile

The layers of a soil profile are like a biography, telling the long-term history of a soil, but they also tell a shorter-term story about what happens with water and plant nutrients as crops are grown each year.

This Soil School episode takes us not quite six feet down in a soil pit in a canola field northwest of Winnipeg, Man., for a discussion about things to look for when digging below the surface.

There are three main properties or things to consider when assessing a soil profile — soil texture, internal drainage, and agricultural capability — the soil’s ability to grow a crop, explains Mitchell Timmerman, agro-ecology specialist with Manitoba Agriculture.

The example shown in this video is a unique Lakeland series soil, which features a clay loam topsoil layer with a sticky clay layer underneath it, followed by alternating layers of sand and silt leftover from the beach of a glacial lake below the topsoil, and then another heavy clay layer at around five feet depth that acts as a floor or pan for water and nutrients that move in water.

“Water is probably going to be fairly slow moving through the stickier clay in the topsoil. Through this initial layer of clay here, and then it will presumably move more easily through this mix of sand and silt, but then once it reaches this really sticky clay at the bottom — the crude metaphor would be a bucket,” says Timmerman. “And that has obvious implications for growing crops here — excess moisture would be an obvious risk.”

Ultimately, understanding how water and nutrients move through a soil profile enables a farmer or agronomist to figure out the best approach for managing fertilizer applications and mitigating risks to crops growing at the soil surface.

Explore a soil pit and the layers in a soil profile with Mitch Timmerman and Kelvin Heppner in this video, filmed at the 2023 4R Field Day at Innovation Farms near Grosse Isle, Manitoba:

(Watch more Soil School episodes here!)

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