Precision and Accuracy of Time Domain Reflectometry and Capacitive Probes to Determine Soil Electrical Conductivity in Cranberry Production – Technical Note

Abstract

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 (R 2 ) between 0.24 and 0.98 and required specific calibration to accurately reproduce the suction lysimeter EC values. The GS3 probes had higher R 2 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 .Key words: electrical conductivity, sandy soils, cranberry, precision farming.Résumé : Dans une étude récente, on laissait supposer que la canneberge est sensible au sel. Si c'est le cas, la conductivité électrique du sol pourrait aider les producteurs à identifier les endroits où la culture subit un stress à cause des dépôts salins. Les auteurs ont recouru à deux sortes de sonde pour estimer la conductivité électrique (CE) ou la conductance (G) : un réflectomètre à dimension temporelle (RDT; modèle CS645) et un détecteur capacitif. Ils ont ensuite comparé leurs estimations à la CE de l'eau dans les pores du sol en utilisant un lysimètre à succion sur un sol sablonneux irrigué de deux façons et exposé à une vaste fourchette de concentrations de sel, en serre. La comparaison de la conductance établie au moyen du RDT avec la CE de l'eau des pores par régression linéaire donne un coefficient de détermination (R 2 ) de 0,24 à 0,98; en outre, il faut procéder à un étalonnage spécifique pour reproduire la CE obtenue avec le lysimètre à succion. Le coefficient de détermination obtenu avec la sonde GS3 est plus élevé (de 0,54 à 0,98). Cette dernière est généralement plus facile à utiliser, sa précision est plus grande et sa pente de régression est presque égale à 1, si bien que les résultats sont supérieurs à ceux obtenus avec le RDT. Dans les deux cas, le calcul de la moyenne rehausse la précision de la CE estimée pour la solution de sol, à l'instar de l'étalonnage des sondes pour la CE située entre 0 et 5 dS m −1 . [Traduit par la Rédaction]Mots-clés : conductivité électrique, sols sableux, canneberge, agriculture de précision.

Irrigation and drainage management strategies to enhance cranberry production and optimize water use in North America

“…The decline in photosynthesis and differences in EC were greater when the treatments were drier (i.e., under lower SWP conditions). The study also showed that EC could be reliably monitored with a capacitive probe with no calibration, or with a calibrated time-domain reflectometry probe (Samson et al 2017a). In absence of calibration of the capacitive probe though, the study showed that a 0.21 dS m −1 error is observed, and then, calibration would bring additional accuracy if needed.…”

“…Because cranberry roots grow close to the soil surface, salt accumulation may be detrimental to berry crops (Samson et al 2017a(Samson et al , 2017b. A paucity of information exists on the tolerance of cranberry to ion accumulation in the root zone under field conditions.…”

Field Comparison of Electrical Resistance, Electromagnetic Induction, and Frequency Domain Reflectometry for Soil Salinity Appraisal

“…The first commercial devices that were used to measure σ b were based on the measurement of the soil electrical resistance (ER) by means of four-electrode integrated probes [19]. Nowadays, the ER technique is still arguably the most widely used for σ b measurement, mostly because it is used in the simplified two-electrode sensors that are integrated within the capacitance-conductance combined (CCC) probes [20][21][22]. Other sensors for σ b measurement are based on reflectometry, remarkably in the time domain (TDR) [12,23,24].…”

“…The rapid information obtained with these proximal probes can be readily used in a sustainable agriculture framework for monitoring and, eventually, for decision-making. Empirical or semi-empirical calibrations have been almost always used to estimate σ e from σ b , and since the σ b values obtained with the different available sensors are also different, not only site-specific, but also sensor-proprietary calibrations have been developed [20][21][22]. The calibrations have been developed mostly under laboratory conditions using sandy soils [22,33,34].…”

Precision Agriculture and Soil and Water Management in Cranberry Production — Special Issue

“…Furthermore, showed that water table management can meet 30% of the daily ET demand. However, Samson et al (2017aSamson et al ( , 2017b cautioned that subirrigation may induce plant stress due to increased soil salinity.…”