Observed variations in the ground electrical conductivity (σb*) measurements obtained with EMI instruments depend on several soil proxies that influence crop growth and development such as salinity (σe), contents of water (θw), clay (wc) and organic matter (wom) and bulk density (ρb). However, the relative contributions of all these to σb* are unknown. This knowledge is needed to improve the planning and interpretation of σb* data for precision agriculture applications. Recently, a semi-empirical model has been developed to relate σb* measurements taken with an EM38 device to σe, θw, wc, wom and ρb and also soil temperature (t). In this work this model was subjected to a global sensitivity analysis (GSA) based on the soil data obtained during two surveys carried out, one in summer and the other in autumn, in an ample irrigated area in SE Spain. On the basis of the multiple linear regression meta-models developed for the σb* measurements, these were found to linearly respond to the soil properties (R2 between 0.92 and 0.96) and thus, the GSA could be based on their standardised regression coefficients. According to these, the soil characteristics explain the following percentages of variance in σb* (PV): 30–34 (σe), 8–20 (θw), 32–47 (wc), 0.6–2.6 (wom), 5.7–7.5 (ρb) and 0.3–0.4 (t) with changes from the summer to the autumn season of − 4, − 12 and + 15 in the PV explained by the most influential properties, respectively, σe, θw and wc. The results of the GSA will help the planning and interpretation of σb* measurements for improving crop management.
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The data associated to this article is stored in the public repository Mendeley Data (https://data.mendeley.com/): Visconti, Fernando; de Paz, José Miguel (2020), “Soil and electromagnetic induction surveys in the Vega Baja del Segura and Baix Vinalopó in 2006 and 2010”, Mendeley Data, V1, https://doi.org/10.17632/rh729nhdz3.1. They will be made openly available from 20th October 2020 on.
No specific code was developed in this research.
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We would like to thank the anonymous reviewers and the Editor-in-Chief for their constructing comments.
The first survey of this project was carried out within Project GV 0461/2006, funded by the Generalitat Valenciana, and the second one within Projects CGL2009-14592-C02-01 and CGL2009-14592-C02-02 funded by the Ministerio de Ciencia e Innovación from the Government of Spain and additionally within project Val i+d APOSTD/2010/029 (F. Visconti), funded by the Generalitat Valenciana.
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Visconti, F., de Paz, J.M. Sensitivity of soil electromagnetic induction measurements to salinity, water content, clay, organic matter and bulk density. Precision Agric 22, 1559–1577 (2021). https://doi.org/10.1007/s11119-021-09798-8
- Sensitivity analysis
- Electromagnetic induction
- Water content
- Organic matter