Calibration of Soil Moisture Sensors (ECH2O-5TE) in Hot and Saline Soils with New Empirical Equation
Round 1
Reviewer 1 Report
The methods and conclusions of this paper are not very innovative to some extent, but a large number of different experiments are set up in this paper with rich content and detailed data analysis. You are advised to modify it.
1.When different experimental factors are set up, how to ensure the uniformity of soil samples may directly affect the results.
2. It is mentioned in the paper that many factors affect the accuracy of the sensor. Can we give a reasonable conclusion and the proportion of different factors affecting the sensor
3. The author should know that sandy loam is a type of soil with a certain range. Sand grains, clay grains and soil grains all have a certain range and belong to sandy loam. Were these data measured for different soil conditions in the paper? Do the parameters obtained in Table 6 change with the change of sand, clay and soil grains?
4. In the simplified empirical equation, the units of different variables are different. When constructing the fitting equation, should we consider the normalization of these variables before carrying out the analysis?
Author Response
Comment: The methods and conclusions of this paper are not very innovative to some extent, but a large number of different experiments are set up in this paper with rich content and detailed data analysis. You are advised to modify it.
Response: The methods and conclusions were revised.
Comment: 1. When different experimental factors are set up, how to ensure the uniformity of soil samples may directly affect the results.
Response:
The differences in soil samples were reduced by taking them from one source and in sufficient quantities to conduct all the study experiments, and then mixing them well before dividing them into experimental samples, whose characteristics are shown in Table 1 and 2. While in the texture experiments, they were carried out by mixing different proportions of clay soil to sandy soil, which are shown in Table (3).
Comment: 2. It is mentioned in the paper that many factors affect the accuracy of the sensor. Can we give a reasonable conclusion and the proportion of different factors affecting the sensor
Response:
These sensors work well in soils with a salinity of 2 to 3 dS/m under temperature conditions between 20 and 30 °C. The increase or decrease in salinity above the mentioned limits, as well as temperatures, leads to an increase or decrease in the readings of sensors, the value of which is determined by the second-degree equation mentioned. Different effects were observed for the rest of the factors studied, but in proportions that we could not determine due to their interference with the salinity effect in the test sample.
Factors can be arranged according to their influence on the readings of the hygrometer as follows: salinity > temperature > texture > organic matter > moisture content of the soil > soil density.
Comment: 3. The author should know that sandy loam is a type of soil with a certain range. Sand grains, clay grains and soil grains all have a certain range and belong to sandy loam. Were these data measured for different soil conditions in the paper? Do the parameters obtained in Table 6 change with the change of sand, clay and soil grains?
Response:
The mechanical and chemical analysis of the entire study was carried out in the laboratories of the Department of Soil Sciences, College of Food and Agricultural Sciences - King Saud University, which are shown in tables (1), (2), (3), as well as different percentages of sand and clay were mixed to form a loam soil according to the triangle of the texture to obtain the parameters mentioned in Table (6). The values of these parameters were observed to change with soil texture, but the differences in the readings were not significant when the parameter values were taken to their nearest consistency.
Comment: 4. In the simplified empirical equation, the units of different variables are different. When constructing the fitting equation, should we consider the normalization of these variables before carrying out the analysis?
Response:
The units have been consolidated: salinity units to (dS/m), temperature units to (°C) and moisture units to (m3 m-3).
Author Response File: 
Author Response.docx
Reviewer 2 Report
The language presentation and the article structure need much improvement. Six factors that affect the measurement accuracy of soil moisture sensors are presented in the paper. However, it is only indicated that conductivity and temperature are affected in the abstract, and the effect of temperature is not explained clearly. The authors consider to add a process diagram of the experimental procedure to illustrate. The experimental procedure revolved around salinity and temperature under different conditions, with insufficient consideration of soil organic matter and soil texture as mentioned in the introduction. The structure of the article was not clear enough, while the explanation of the graphs in the results was not sufficient. Consider to add analysis of experimental data in the results section. The comparison of the measured values of the soil moisture sensor with the true values measured by the gravimetric method is misleading in the figure. The authors may consider combining the analysis results with the true values measured by the weight method under different constraints, and may consider replacing the added water in the x-axis of the graph with the volumetric water content. The empirical equation presented in the results consists of a polynomial in temperature and dielectric constant, is it reasonable and does it reflect the consideration of soil texture and organic matter in this study.
In addition,
1. Consider separate description of the study results in the abstract.
2. The interactions between soil moisture sensor measurement accuracy and the effect factors were not specified in the introduction, and their improved accuracy in previous studies.
3. Consider mentioning the paper: Bingze, L., Chunmei, W., Xingfa, G., Xiang, Z., Ming, M., Lei, L., Zhuangzhuang, F., Tianyu, D., Xiaofeng, L., Tao, J., Xiaojie, L., Xingming, Z. Accuracy calibration and evaluation of capacitance-based soil moisture sensors for a variety of soil properties. Agricultural Water Management. 2022, 273, 107913. https://doi.org/10.1016/j.agwat.2022.107913.
Yuhi Satoh, Hideki Kakiuchi. Calibration method to address influences of temperature and electrical conductivity for a low-cost soil water content sensor in the agricultural field. Agricultural Water Management. 2021, 255, 107015. https://doi.org/10.1016/j.agwat.2021.107015.
The authors analyzed the relationships of several effect factors on the measurement accuracy of soil moisture sensors.
4. The description of the 5TE soil moisture sensor is not uniform in the paper.
5. Insufficient description of 5TE soil moisture sensor.
6. Page 1, line 15. “While” should be revised to “while”
7. Page 4, line 99 to line 100. The units of latitude and longitude need to be standardized.
8. The RMSE and CRM for the different limitations in the figure were not explained in the results section.
9. Page17, line 357 a, b
Comments for author File: 
Comments.pdf
Author Response
Reviewer # 2
Comment: The language presentation and the article structure need much improvement. Six factors that affect the measurement accuracy of soil moisture sensors are presented in the paper. However, it is only indicated that conductivity and temperature are affected in the abstract, and the effect of temperature is not explained clearly. The authors consider adding a process diagram of the empirical procedure to illustrate. The empirical procedure revolved around salinity and temperature under different conditions, with insufficient consideration of soil organic matter and soil texture as mentioned in the introduction. The structure of the article was not clear enough, while the explanation of the graphs in the results was not sufficient. Consider to add analysis of empirical data in the results section. The comparison of the measured values of the soil moisture sensor with the true values measured by the gravimetric method is misleading in the figure. The authors may consider combining the analysis results with the true values measured by the weight method under different constraints and may consider replacing the added water in the x-axis of the graph with the volumetric water content. The empirical equation presented in the results consists of a polynomial in temperature and dielectric constant, is it reasonable and does it reflect the consideration of soil texture and organic matter in this study.
Response:
-The effect of salinity and temperature factors on the readings of the devices are clear independently, while the rest of the factors overlap with the effect of the salinity factor, and some parameters were determined in the equation according to the differences in soil texture, but we were not able to isolate the effect of the organic matter factor from the effect of salinity in the samples studied.
-Some additional explanations have been added in the figures and in the results.
-A graph has been attached that combines the results of analyzing the various factors affecting the readings with the real values of moisture content by weight method, as well as by calculating the water added during the experiment.
-The empirical equation was derived after collecting a large group of sensor readings results against real gravimetric moisture method of soil samples with different properties in texture, and collecting the various resulting equations to build an empirical equation by changing the parameter values and repeating the experiment to find the values of the different parameters in the equation that are closer to the average values. Three different soils in terms of texture (sand-loam-clay) were tested. The presented empirical equation was also applied to a large group of soils and gave reasonable results. However, regarding the organic matter, it was noted that there is an overlap between the effect of the organic matter and the concentration of salts in it, and therefore we were not able to find parameters specific to the organic matter in the equation.
In addition,
Comment: 1. Consider separate description of the study results in the abstract.
Response:
A separate description of the study results has been added to the abstract
Comment: 2. The interactions between soil moisture sensor measurement accuracy and the effect factors were not specified in the introduction, and their improved accuracy in previous studies.
Response:
The interaction between the accuracy of measuring sensors and the influencing factors was explained in the introduction: The relationship between the actual soil moisture by graphametric method and the soil moisture measured by the sensors is always a direct relationship.
Comment: 3. Consider mentioning the paper: Bingze, L., Chunmei, W., Xingfa, G., Xiang, Z., Ming, M., Lei, L., Zhuangzhuang, F., Tianyu, D., Xiaofeng, L., Tao, J., Xiaojie, L., Xingming, Z. Accuracy calibration and evaluation of capacitance-based soil moisture sensors for a variety of soil properties. Agricultural Water Management. 2022, 273, 107913. https://doi.org/10.1016/j.agwat.2022.107913.
Yuhi Satoh, Hideki Kakiuchi. Calibration method to address influences of temperature and electrical conductivity for a low-cost soil water content sensor in the agricultural field. Agricultural Water Management. 2021, 255, 107015. https://doi.org/10.1016/j.agwat.2021.107015.
The authors analyzed the relationships of several effect factors on the measurement accuracy of soil moisture sensors.
Response:
The results of the mentioned references have been reviewed and References were added.
Comment: 4. The description of the 5TE soil moisture sensor is not uniform in the paper.
Response :
The soil moisture sensor has been re-described
Comment : 5. Insufficient description of 5TE soil moisture sensor.
Response:
The soil moisture sensor has been re-described
Comment: 6. Page 1, line 15. “While” should be revised to “while”
Response: Done
Comment: 7. Page 4, line 99 to line 100. The units of latitude and longitude need to be standardized.
Response: Done
Comment:8. The RMSE and CRM for the different limitations in the figure were not explained in the results section.
Response: Done
Comment: 9. Page17, line 357 a, b
Response: Reference has been corrected too and many thanks to you.
Author Response File: Author Response.docx
