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Ask the Agronomist: Why is Soil Tension Important for Monitoring Different Soil Types?

Ben Smith Director of Grower SupportAt a recent grower seminar in Yakima Valley, Washington, Hortau Director of Grower Support Ben Smith discussed a number of topics during his presentation on “Irrigation Management Basics.”

One of the more intriguing topics for the 50 growers on hand revolved around how soil tension (and other types of measurements for that matter) varies across different soil types. In Washington, like many major agricultural regions, growers farm across a number of vastly different soil types often times on the same operation.

Which begs the question: Why is soil tension important for monitoring crop stress across different soil types?

Anyone who has used Hortau’s soil tension monitoring system understands its tensiometers don’t have to be calibrated due to soil type and aren’t affected by salinity or alkalinity like some other sensor technologies on the market.

In our 16 years of experience, we’ve found soil type is often the biggest factor in determining the precise amount of available water to a growing crop, and if your sensor only measures a percentage of water in the soil, you’re not seeing the big picture.

For example, a water content probe may show 20% water content in a sandy soil, which results in soil tension of 5 cbar (a non-stressed, ideal situation for a crop). But in clay soil, a 20% water content reading is a whole other story. In clay soil, 20% water content could result in severe stress (60 cbar), because water isn’t as readily available to a crop in clay soil versus sandy soil.

So in this case, 20% water content in a sandy soil is drastically different than 20% in clay soil. But if you were measuring soil tension in real time with Hortau, you’d be able to pin point crop stress thresholds and clearly see the differences between 5 cbar (non-stressed) versus 60 cbar (severely stressed) across various soil types. These soil tension readings allow growers to anticipate and mitigate stress, keeping your crop in the ideal stress range all season long via proper irrigation management.

“Overall, sandy soils hold more water than clay soils,” Smith said. “This is contrary to what a lot of us learned growing up. We go to school and we hear clay soils hold water, sand doesn’t hold water. That’s true in terms of a broad scale and a percentage of water, but in terms of soil tension and the range that we prescribe for proper irrigation management, the opposite is true: sandy soils hold more available water.”

Contact us today to learn more about Hortau’s soil tension monitoring service, and how we help growers optimize production across various soil and crop types.