Predicting Soil Properties for Agricultural Land in the Caucasus Mountains Using Mid-Infrared Spectroscopy

Round 1

Reviewer 1 Report

The authors have presented a study on the estimation of certain soil properties using mid-infrared spectroscopy. The manuscript is comprehensively written, with clear material and methods, and well-detailed and discussed results. In studies of this nature, the calibration and validation processes are crucial, and the authors have provided thorough descriptions of these processes. However, before publication, two points require clarification:

1. Please specify whether there are replicates of the soil samples.
2. Justify the choice of the number of soil samples (114) by referencing similar studies with sample sizes close to 114 to strengthen the robustness of the findings.

English is adequate.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript titled “Predicting soil properties for agricultural land in the Caucasus Mountains using mid-infrared spectroscopy” focused on the fast determination of soil properties based on mid-infrared spectroscopy, which is significant to land surveys, digital soil mapping, precision agriculture and the classification of soil attributes at different scales and in various climatic regions.

   However, there are several issues that need to be discussed: 1) in the abstract, the author writed “The aim of this study was to compare the spectra recorded with two portable instruments, the Agilent 4300 Handheld (MIR-FTIR) and the ASD Field- SpecPro (Vis-NIR) for predicting soil properties in …….”  However, in fact, this paper only studied the spectral characteristics of soil-related attributes based on Agilent 4300 Handheld (MIR-FTIR), suggesting modification and improvement. 2. The text in lines 375-381 and 418-424 were completely repeated, please revise. 3) In this manuscript, “the interpretation of MIR spectra allowed to differentiate non-carbonated and carbonated samples corresponding to CaCO3 leaching and accumulation zones associated with topography and land use.”, but the authors did not present or analyze the background of 114 soil samples, such as soil parent material, land use type, etc., and precipitation, where Figure 2.was the histograms and descriptive statistics of the tested soil properties (n=114). It is suggested that the author classify the soil samples according to the land use type or soil type, and show their spectral characteristics and nutrient content, so as to make the conclusion of this paper reliable. 

The manuscript titled “Predicting soil properties for agricultural land in the Caucasus Mountains using mid-infrared spectroscopy” focused on the fast determination of soil properties based on mid-infrared spectroscopy, which is significant to land surveys, digital soil mapping, precision agriculture and the classification of soil attributes at different scales and in various climatic regions.

   However, there are several issues that need to be discussed: 1) in the abstract, the author writed “The aim of this study was to compare the spectra recorded with two portable instruments, the Agilent 4300 Handheld (MIR-FTIR) and the ASD Field- SpecPro (Vis-NIR) for predicting soil properties in …….”  However, in fact, this paper only studied the spectral characteristics of soil-related attributes based on Agilent 4300 Handheld (MIR-FTIR), suggesting modification and improvement. 2. The text in lines 375-381 and 418-424 were completely repeated, please revise. 3) In this manuscript, “the interpretation of MIR spectra allowed to differentiate non-carbonated and carbonated samples corresponding to CaCO3 leaching and accumulation zones associated with topography and land use.”, but the authors did not present or analyze the background of 114 soil samples, such as soil parent material, land use type, etc., and precipitation, where Figure 2.was the histograms and descriptive statistics of the tested soil properties (n=114). It is suggested that the author classify the soil samples according to the land use type or soil type, and show their spectral characteristics and nutrient content, so as to make the conclusion of this paper reliable. 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Aim and major conclusions

The present paper compares the spectra recorded with two portable instruments, namely the Agilent 4300 Handheld (MIR-FTIR) and the ASD Field-15 SpecPro (Vis-NIR) operating with mid-infrared (MIR) and visible-near infrared (Vis-NIR) spectroscopy correspondingly.  Samples were taken from 114 sites located in the Kastanozem predominating agricultural land and measurements concerned with 17 soil properties. 

The paper assessed the accurateness of the methods and found them to be high, although for different soil characteristics. However, MIR and Vis-NIR spectroscopy capture similar soil information and this does not provide scope for combining the spectral ranges.

Evaluation

This is a well written technical paper on soil analysis methodology. In particular, it tests the performance of a MIR-FTIR portable spectrometer for predicting soil properties in heterogeneous land and compares its prediction competence to Vis-NIR spectra. 

Minor points and possible improvements

1) The authors can make the introduction more readable by:

a) differentiating the aims and objectives from the literature review. For example, they can keep the first para (43-53) with the last one (138-152) as "aims and objectives" sub-section and the rest as "literature review" sub-section.

b) Explaining more why the accuracy of portable spectroscopy is of interest and provide some examples from the literature which link the spectral methods with cost efficiency, time savings or any other advantage of portable spectral methodology. 

2) The title of sub-section 2.2. "Chemical Analyses and Descriptive Statistics" may be misleading since there are no any descriptive statistics in there.    

3) Conclusions lack revisiting the aims and objectives of the paper and addressing them one-by-one. I would also like to see a "what next" discussion and proposals for further research in the methods.

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

Dear Authors,

you have prepared a very interesting manuscript on the prediction of soil properties for agricultural land of the Caucasus using infrared spectroscopy.

In my opinion, the manuscript is well written, according to the IMRAD system.

The abstract is thematically related to the overall text.

In the introduction you have included the most important introductory information on the subject. The whole is coherent and logical.

You have described the results clearly, you have described the research methodology well, you have included interesting images.

You developed the results very logically and understandably. The tables are clear and contain valuable data.

The discussion, in my opinion, needs a small correction. I ask you to refine this part of your work by adding a minimum of 10 scientific articles from the last 10 years thematically related to your research. 

Literature sources correctly selected and cited. 

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The revised version of the paper has met the publication requirements, and I agree to publish it.

The revised version of the paper has met the publication requirements, and I agree to publish it.