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Precision and accuracy of time-domain reflectometry and capacitive probes to determine soil electrical conductivity in cranberry production — Technical note1

Samson, M.-E., Caron, J., Pepin, S., Parys, B., Fortin, J.
Canadian journal of soil science 2016 v.97 no.1 pp. 31-37
cranberries, electrical conductivity, greenhouses, growers, irrigation, lysimeters, monitoring, reflectometry, regression analysis, salt stress, sandy soils, soil pore water, soil solution
A recent study suggests a sensitivity of cranberry to saline stress. Consequently, monitoring of soil electrical conductivity may help growers to identify areas where plants could be under stress due to salt deposits. We used two different types of probes, a time-domain reflectometry (TDR; model CS645 probe) and a capacitive approach (model GS3 probe) to estimate electrical conductivity (EC) or conductance (G). The estimates were compared with measurements of EC in soil pore water using suction lysimeters in a sandy soil exposed to two different irrigation methods and a wide range of salt concentrations in a greenhouse. Linear regression analysis of TDR conductance versus measured EC in pore water gave coefficients of determination (R²) between 0.24 and 0.98 and required specific calibration to accurately reproduce the suction lysimeter EC values. The GS3 probes had higher R² values, between 0.54 and 0.98, and were generally easier to work, gave a better accuracy, and had a regression slope not significantly different from 1, result better than with the TDR probes. For both probes, data averaging increased the accuracy in estimates of soil solution EC, as did specific calibration of the probes for the EC values value within the range of 0–5 dS m⁻¹.