the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Electromagnetic and DC-current geophysics for soil compaction assessment
Abstract. Monitoring soil structure is of paramount importance due to its key role in the critical zone as the foundation of terrestrial life. Variations in the arrangement of soil components significantly influence its hydro-mechanical properties, and therefore its impact on the surrounding ecosystem. In this context, soil compaction resulting from inappropriate agricultural practices not only affects soil ecological functions, but also decreases the water-use efficiency of plants by reducing porosity and increasing water loss through superficial runoff and enhanced evaporation.
In this study, we compared the ability of electric and electromagnetic geophysical methods, i.e. Electrical Resistivity Tomography and Frequency-domain Electromagnetic Method, to assess the effects of compaction on agricultural soil. The objective was to highlight the electro-magnetic response caused by both heavy plastic soil deformations generated by a super-heavy vehicle and the more common tractor tramlines.
DC-current prospecting has finer spatial resolution and allows a tomographic approach, requiring higher logistic demands and the need for ground galvanic contact. On the other hand, contactless electromagnetic induction methods can be quickly used to define the distribution of electrical conductivity in the shallow subsoil in an easier way. Results, validated with traditional soil characterization techniques (i.e. penetration resistance, bulk density and volumetric water content on collected samples), show the pros & cons of both techniques and how differences in their spatial resolution heavily influence the ability to characterize compacted areas with good confidence. This work aims at contributing to the methodological optimization of agro-geophysical acquisitions and data processing, in order to obtain accurate soil models through a non-invasive approach.
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RC1: 'Comment on egusphere-2024-1587', Anonymous Referee #1, 09 Aug 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1587/egusphere-2024-1587-RC1-supplement.pdf
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AC1: 'Reply on RC1', Alberto Carrera, 26 Aug 2024
Dear Anonymous Referee,
we sincerely thank you for your precious contributions to improve our manuscript.
All your comments have been considered and answered. Please find below our answers to them, considering that the reference lines refer to the clean version of the revised manuscript.Sincerely
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AC1: 'Reply on RC1', Alberto Carrera, 26 Aug 2024
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RC2: 'Comment on egusphere-2024-1587', Anonymous Referee #2, 13 Aug 2024
The use of geophysical methods in the field of agriculture is gaining in popularity, as this article demonstrates. The authors compare two geophysical methods: Electrical Resistivity Tomography (ERT) and the Frequency Domain Electromagnetic Method (FDEM), to assess the state of the soil as a result of agricultural practices that increase its compaction and compromise its hydromechanical properties. Knowing the state of agricultural soil is of paramount importance to better understand how to manage future cultivation, especially in terms of irrigation and nutrients. I thank the authors for this important work that demonstrates how geophysical techniques can be of great support in evaluating agricultural practices and especially in knowing the state of the soil, in order also to reduce water wastage without compromising the physical state of the soil.
The article is well structured and I find it suitable for the special issue on Agrogeophysics.
Some suggestions:
Emphasise in the abstract the importance and innovative aspect of the work.
Improve Fig1, showing in the legend the meaning of everything in the figures.
Indicate in the figure the transects on which the FDEM surveys were carried out.
Line 230-235 Sure FDR? The volumetric content was measured with a TDR sensor.Congratulations on a job well done and all the best!
Citation: https://doi.org/10.5194/egusphere-2024-1587-RC2 -
AC2: 'Reply on RC2', Alberto Carrera, 26 Aug 2024
Dear Anonymous Referee,
we sincerely thank you for your precious contributions to improve our manuscript.
All your comments have been considered and answered. Please find below our answers to them, considering that the reference lines refer to the clean version of the revised manuscript.Sincerely
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AC2: 'Reply on RC2', Alberto Carrera, 26 Aug 2024
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RC3: 'Comment on egusphere-2024-1587', Anonymous Referee #3, 02 Oct 2024
General Summary
The manuscript presents a comprehensive comparison between two geophysical techniques, Electrical Resistivity Tomography (ERT) and Frequency-domain electromagnetic Method (FDEM), for assessing soil compaction in agricultural contexts. It effectively highlights the strengths and limitations of both methods, with a focus on their resolution and efficiency in characterizing soil structure at various scales. The study offers valuable insights into the applicability of these non-invasive methods for improving soil monitoring in agriculture, contributing to the optimization of geophysical data acquisition and processing. The results are well-supported by traditional soil characterization techniques and validated with traditional soil characterization techniques (penetration resistance, bulk density, volumetric water content), making the findings relevant for advancing agriculture practices and enhancing the understanding of soil-plant-water interactions.
I would like to acknowledge the authors for their contribution to addressing the practical limitations and potential of sensor technologies in soil monitoring. This manuscript is a strong candidate for inclusion in the special issue: Agrogeophysics, as it provides important insights into the performance of geophysical methods in agricultural applications. I recommend a minor revision to further refine the clarity and presentation of the findings.
I appreciate the authors for their valuable contribution to setting realistic expectations regarding sensor efficacy. I believe this manuscript is suitable for inclusion in EGUsphere, as it provides important insights into the performance of geophysical methods in agricultural applications. However, I believe that there are some points that can be improved. Therefore, I recommend a major revision.
All the best!
General comments –
- Please revise the abstract to reflect the specific objectives, methods, and findings of the study more clearly.
- Please review and correct the usage of abbreviations throughout the manuscript.
- Please re-check the figures and figure captions.
Specific comments –
Title – Suggest modifying the title as "“Electrical and electromagnetic geophysics for soil compaction assessment”
Abstract – Lines 5 – 15: the introduction sentences of the abstract should be specific to the present study
Lines 10 – 15 – “agricultural soil”, Please specify the soil – “silt loam”
Lines 10-15 – Please refine the objective in the abstract specific to the study
Lines 15 – 20 – Please provide an overall methodology statement (one sentence) including the methods of different analysis (correlations, K means clustering etc.)
Lines 20 – 25 – Please include the overall finding of this study in the abstract.
Lines 30 – 35 – “Soil properties, agricultural processes, and moisture dynamics.” Please include state variables as well to represent soil water content and soil salinity.
Lines 45 – 50 – “EC” please define the abbreviation in the first place
Lines 60 – 65 – “Soil electrical conductivity (EC)” should be soil EC
Lines 60 – 65 – Soil EC is also used to estimate soil water content and soil salinity – please include that as well
Lines 75 – 80 – “with increased electrical conductivity” should be “with increased EC”
Lines 80 -85 – “for the assessment of soil surface compaction.” – readers would like to know the depth, if possible, please provide the depth range within brackets.
Lines 80 85 – “The survey was conducted both at the field scale, covering an area of 1.5 hectares, and in detail on individual targeted transects”. Please rephrase the sentence for clarity.
Lines 90 -95 – “Results, validated with direct information, show the pros & cons of both FDEM and ERT techniques and how differences in their spatial resolution heavily influence their ability to characterize compacted areas with good confidence.” This content does not fit here. Please remove or modify.
Figure 1 – Fig. 1b – “FDR”? Is this “TDR”?
Fig. 1c - It is difficult to understand where this matches with Figure 1. B, please modify the figures and clearly show the figure c in figure b.
Heading 2.2 – Please remove the abbreviation – already introduced
Lines 115 – 120 – “Electro-Magnetic” should be electromagnetic
Lines 120 – 125 – “Electrical conductivity (EC)” already introduced – please use EC
Lines 120 – 125 – “can be probed” please replace as “can be obtained”
Line 130 – “4m” should be “4 m”; please keep a space between the number and the unit.
Heading – 2.3 – Please remove the abbreviation
Lines 160 -165 – “first few centimetres of the soil”, please provide a number, how many centimetres.
Lines 165 – 170 – “Q=2%” Please provide what is “Q”?
Lines 175 – 180 – “Both geo-electric and electromagnetic,” Please use a consistency term to represent ERT. For example, “Both electrical and electromagnetic”
Lines 175 – 180 – In Fig. 1C, it is difficult to understand the discussed lines in this sentence “an initial areal FDEM acquisition was followed by 3 additional lines to intercept seeder heavy passages, and 8 detailed transects, both FDEM and ERT (4 along and 4 across normal tractor tramlines. Please modify the Fig. 1C for clarity.
Line 185 – “ dij" should be “dih”?
Lines 185 – 190 – “For each area, one geophysical detailed survey (i.e. ERT + FDEM) was performed.” Please rewrite this sentence for clarity. One geophysical detailed survey or both surveys (ERT + FDEM)?
Lines 190 – 195 – “throughout the 0–80 cm soil layer.” Please provide the soil sampling depth intervals. Same in “ 0.70 m” as well.
Lines 195 – 200 – “bulk density” should be “BD”, “4m” should be “4 m”
Lines 200 – 205 – “22cm” should be “22 cm”
Heading 3.1 – What is mean by “First” here
Lines 215 – 220 – Please introduce the abbreviations (VCP0.32 and HCP1.18) in the first use.
Lines 220 – 225 and Figure 2a - I'm just wondering why the legend of Fig 2a ranges only to 30 mS/m and not 40 mS/m. In the content authors mentioned, “In the bottom layer (HCP1.18), a maximum increase of approximately 15 mS m-1 is observed, with values exceeding 40 mS m-1 in the most conductive zones”
Figure 2.a – Please rearrange the overlapped labels
Figure 3 – “a” should be removed. The sample symbol in the legend is different from the map.
Lines 230 – 235 – “FDR” should be “TDR”
Figure 4 – VWC, please introduce the abbreviation first.
Lines 240 – 245, and 255 – 260 – Why the unit for water content in kg/kg Please correct the unit of volumetric water content to m3/m3, as similar to the figure 5.
Lines 320 -325 – Please remove the already introduced abbreviations.
Lines 340 -345 – “In both areal and detailed surveys, the highly compacted portions of the soil are characterized by high electrical conductivity anomalies relative to the context.” What would be the reason for this observation, please discuss.
Lines 375 – 380 – It would be nice if the authors could mention the most important challenges here. “Despite its potential and widespread application, the use of electromagnetic geophysics in agriculture presents challenges such as…...”
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AC3: 'Reply on RC3', Alberto Carrera, 09 Oct 2024
Dear Anonymous Referee,
we sincerely thank you for your precious contributions to improve our manuscript.
All your comments have been considered and answered. Please find below our answers to them, considering that the reference lines refer to the clean version of the revised manuscript.Sincerely
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