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Theory and Guidelines for the Application of the Geophysical Sensor EM38
Open AccessCommunication

Low-Input Estimation of Site-Specific Lime Demand Based on Apparent Soil Electrical Conductivity and In Situ Determined Topsoil pH

1
Department of Biobased Products and Energy Crops (340b), Institute of Crop Science, University of Hohenheim, Fruwirthstr. 23, 70599 Stuttgart, Germany
2
Institute of Agricultural Engineering, Kiel University, Olshausenstr. 40, 24098 Kiel, Germany
*
Authors to whom correspondence should be addressed.
Sensors 2019, 19(23), 5280; https://doi.org/10.3390/s19235280
Received: 31 October 2019 / Revised: 28 November 2019 / Accepted: 28 November 2019 / Published: 30 November 2019
(This article belongs to the Special Issue Sensors in Agriculture 2019)
Site-specific liming helps increase efficiency in agricultural production. For adequate determination of the lime demand, a combination of apparent soil electrical conductivity (ECa) and topsoil pH can be used. Here, it was hypothesized that this can also be done at low-input level. Field measurements using the EM38 MK I (Geonics, Canada) were conducted on three experimental sites in north Germany in 2011. The topsoil pH was measured based on two approaches: on the field using a handheld pH meter (Spectrum-Technologies Ltd., Bridgend, UK) with a flat electrode (in situ), and in the lab using standard equipment (ex situ). Both soil ECa (0.4–35.9 mS m−1) and pH (5.13–7.41) were heterogeneously distributed across the sites. The same was true of the lime demand (−1.35–4.18 Mg ha−1). There was a significant correlation between in situ and ex situ determined topsoil pH (r = 0.89; p < 0.0001). This correlation was further improved through non-linear regression (r = 0.92; p < 0.0001). Thus, in situ topsoil pH was found suitable for map-overlay with ECa to determine the site-specific lime demand. Consequently, the hypothesis could be confirmed: The combined use of data from EM38 and handheld pH meters is a promising low-input approach that may help implement site-specific liming in developing countries. View Full-Text
Keywords: liming; precision farming; EM38; soil acidity; digital soil mapping liming; precision farming; EM38; soil acidity; digital soil mapping
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von Cossel, M.; Druecker, H.; Hartung, E. Low-Input Estimation of Site-Specific Lime Demand Based on Apparent Soil Electrical Conductivity and In Situ Determined Topsoil pH. Sensors 2019, 19, 5280.

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  • Supplementary File 1:

    PDF-Document (PDF, 119 KB)

  • Externally hosted supplementary file 1
    Doi: 10.5281/zenodo.3523331
    Link: https://zenodo.org/record/3523331#.Xbnf3xsiFhE
    Description: Overview of combined observations for soil apparent electrical conductivity (via EM38 MK1 (Geonics, Mississauga, Canada) in vertical mode), soil humidity, ex situ determined topsoil pH (pHREF), in situ determined topsoil pH (pHFE), modified in situ determined topsoil pH (pHFEM2) and the respective estimated lime demands based on ECa and pH (pHREF, pHFE, pHFEM2) values.
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