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Soil Moisture Release Curves

The trouble with moisture release curves

Creating soil moisture release curves has always been tricky. Traditional methods require a ton of work, are limited by a lack of data points, and can take several months just to complete a partial curve. Plus, there’s never been an easy way to measure the range of soil water potential for an entire curve. Until HYPROP 2.

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Simply accurate. Simply fast. Simply automated.

As soil scientists who have made hundreds of soil moisture release curves, we wanted an instrument that delivered greater accuracy. And we demanded an instrument that was automated. The HYPROP 2 takes only days vs. months to generate a soil water characteristic curve in the wet range, and it does this automatically.

Use the HYPROP 2 together with the WP4C (which measures the dry range), and you can create full, high-resolution moisture release curves across the entire range of soil moisture. Nothing else is capable of doing that—not at this level of detail.

Sampling ring flexibility

On top of all that, we designed the HYPROP 2 to automatically determine unsaturated hydraulic conductivity on undisturbed soil samples placed inside a standard 250 mL or 100 mL, 2 in diameter sampling ring. Used in tandem with the KSAT, it can a generate a hydraulic conductivity curve for any soil type. The resulting instrument winds up saving you time, hassle and worry.

Unrivaled accuracy

When it comes to soil water potential, measurements don’t get any more accurate or precise. That’s because the HYPROP 2 produces more data points (over 100 data points in the 0 to -100 kPa range), higher resolution data, more detail, and better information in its moisture release curves—information that is missed when using the traditional pressure plates or hanging water column methods.

The HYPROP 2 uses two precision mini-tensiometers to measure water potential at different levels within a saturated soil sample while the sample rests on a laboratory balance. Over time, the sample dries, and the instrument measures the changing water potential and the changing sample weight simultaneously. It calculates the moisture content from the weight measurements and plots changes in water potential correlated to changes in moisture content.

The faster, the better

After setup, the HYPROP 2 is capable of generating a soil moisture characteristic curve and determining the unsaturated hydraulic conductivity of soil samples in only days versus months. To save you even more time, it can operate while being left unattended.

Automated everything

The HYPROP 2 is a complex instrument, but it makes soil moisture release curves much simpler. While other methods require weeks of tedious drying and weighing, the HYPROP 2 can be set up to run automatically. Its software calculates values for dry range and saturation according to a selected model, and it even allows you to input data from other water potential instruments such as the WP4C to automatically fit the soil moisture release curves.


The expert on soil moisture release curves (so you don’t have to be)

HYPROP 2 generates the best data on the wet end of the soil water characteristic curve, with more details than any instrument on the market. Plus, you can combine the HYPROP 2 with any LABROS instrument for a complete soil analysis—the PARIO for soil particle size analysis, the WP4C for a complete moisture release curve, or the KSAT for a hydraulic conductivity curve. The result? Powerful tools for understanding data and predicting a soil’s behavior over time.

Unparalleled accuracy. Automation. Far faster speeds. The HYPROP 2 meets the highest lab instrumentation standards, giving you results you can trust with far less work and hassle.

Feature summary

  • More precise and robust

  • Low time, cost, and effort

  • Easy to handle and flexible

  • Simultaneous measurement of water retention function and hydraulic conductivity

  • High validity of the water retention function, especially in the area close to saturation

  • The hydraulic functions are consistently verified by a large number of measuring values

  • Reliable determination of unsaturated conductivity in the medium water potential range—independent of model assumptions

  • Tensiometers measure beyond typical cavitation point down to -240 kPa

  • Tensiometers are positioned upside down in the soil sample (undisturbed evaporation and no impact on the tensiometer shafts)

  • Reduced tensiometer water loss after reaching the cavitation phase

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