Evaluation of ion-selective electrode methodology for integrated on-the-go mapping of soil chemical properties (pH, K & NO₃)

Knowledge of the spatial variability of soil attributes is critical for precision agriculture. Different approaches to assess this variability on-the-go have been taken through development of soil sensors. A new ion-selective electrode (ISE) based approach was implemented for simultaneous mapping of soil pH, residual nitrate (NO₃) and soluble potassium (IC) contents. In this publication, the results of laboratory experiments investigating the effects of key measurement parameters are reported. These parameters include: soil-water ratio (SWR), quality of water used for electrode rinsing (QWR) and for ion extraction (QWE), presence of ionic strength adjuster (ISA) and solution agitation (stirring). Based on this study involving four different soils, the following measurement parameters were recommended: agitated purified water extraction without ISA, addition of a fixed amount of water (preferably 1:1 soil-water ratio), and regular (tap) water for electrode rinsing.