One of the challenges for irrigated potato production in Manitoba is that potatoes are quite sensitive to salinity. Mapping salinity in a field is done via Veris, which measures the electrical conductivity (EC) of the soil. Unfortunately factors such as soil moisture and soil texture can affect the Veris readings, so these readings need to be correlated to actual soil salinity readings.
We’ve tried different methods for correlating the Veris readings to the soil salinity and this is the method that’s worked the best for us so far:
- Map the field with the Veris unit
- Identify sites with high, moderate, and low Veris readings (at least one of each per section, if not per field)
- Soil sample each site at depths of 0-6″, 6-12″, 12-24″, 24-36″, and 36-48″
- Have each sample tested for cation exchange capacity (to identify changes in texture) and saturated paste extractable salt (salinity)
- Correlate the soil test results with the Veris readings
Step 5 is the one I want to look at in more depth.
The Veris readings are 0-30 cm and 0-90cm. This corresponds to 0-12″ and 0-36″. What I do is take the average of the soil samples for those depths and compare them to the Veris reading. I end up with two tables (one for each Veris depth) relating the Veris reading to the averaged soil sample salinity for that depth. Then I create a XY scatter chart with Veris readings as the Y axis and soil electrical conductivity readings as the X axis. I then add a trendline and use the formula from that trendline to estimate the salinity values across the field. These estimated salinity values are then used to draw a lovely map that shows the locations of any saline spots in the field. Then can then be managed appropriately to ensure that they do not spread or affect the production of poatoes.
I’m fairly certain that my methodology as described above could be improved, so if anyone has any suggestions I would appreciate them. Thank you!
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