Taking a soil pH measurement
- Calibrate first — using the supplied pH 4.01 and pH 7.00 buffer solutions. Place a few drops of each buffer directly onto the flat sensor and calibrate the meter regularly with pH 4 and pH 7 calibration solution. The meter has automatic standard recognition, so it identifies which buffer you've applied.
- Prepare the soil sample — because the sensor reads a
liquid/paste film, you need to extract a solution from the soil rather than pressing dry soil directly onto it. The standard approach is a soil:water slurry (commonly 1:1 or 1:2 v/v), mixed, allowed to settle briefly, and then either the supernatant or the moistened paste is applied to the sensor. - Apply the sample — just place a few drops of the sample
onto the flat sensor; minimum sample volume is 0.1ml (or 0.05ml with sampling sheet B). No beaker or immersion is needed thanks to the flat sensor design. - Read the result — record the reading once a smiley face
appears on the display, indicating the reading has stabilized.
Does it require distilled water?
Yes — distilled or deionized water is the standard for the extraction step. Soil testing with LAQUAtwin involves extracting a sample solution with distilled water and measuring the pH and conductivity of the extract, with an ideal pH range around 5.4-6.2 in some crop-specific guidance (e.g., coconut coir). Tap water shouldn't be used because its own mineral content and pH can
skew the reading. Consistency in your soil:water ratio and using the same water source each time is what makes readings comparable over seasons.
Actions after obtaining a reading:
- Compare against crop-specific optimal pH ranges — most fruit crops have fairly narrow target windows (e.g., many tree fruits prefer 6.0-6.8; blueberries and some others want much more acidic soil, 4.5-5.5).
- Decide on amendment direction: if too acidic, lime application; if too alkaline, sulfur or acidifying amendments.
- Cross-check with a lab test periodically — the LAQUAtwin is excellent for rapid field screening and trend-spotting, but a full lab soil test (with buffer pH, CEC, nutrient panel) is worth running periodically to calibrate your field readings and catch anything the quick method might miss.
- Log readings spatially — since pH can vary meaningfully across a field or orchard block, tagging readings to GPS points lets you build a pH map rather than relying on a single average, so lime/sulfur can be applied variably where it's actually needed. We recommend the geodatatrack program.
- Re-test after amendment — pH corrections take time to work through the soil profile (lime especially can take months), so re-test at a sensible interval rather than expecting an immediate shift.
Sensor storage — does it need to be kept damp?
No — this is actually the opposite of what many assume. The pH sensor should be stored in dry condition; distilled or deionized water should never be left on the pH sensor for a long period, as salts may leach out and reduce sensor life.
Before your next use, the sensor should be conditioned again prior to use (typically a brief soak or conditioning solution step per the manual) rather than kept permanently wet in storage. Rinse the sensor with water after each use, dry it, and store it dry — then recondition before the next measurement
session.
