Life-Cycle Energy, Economic, and Greenhouse Gas Emissions of Diversified Sweet-Potato-Based Cropping Systems in South China
Round 1
Reviewer 1 Report
I read through your paper very carefully, and it presents some interesting considerations and contributions. First of all, I found the focal research objective based on your study very interesting given the relevance of the sector in terms of environmental issues. Thus, the analysis of efforts made in this field is commendable and deserves further investigation. However, some considerations and suggestions should be highlighted.
First of all, I'd have appreciated more depth from the literature background analysis.
Secondly, I'd explain better the relevance of the selected region and whether the analysis could be replicated in others too.
Further on, I suggest enlarging the conclusion section in order to highlight the potential of the paper, its contribution as well as future developments.
The paper is relevant and I believe that - if implemented - it could represent a boost in LCA literature
Author Response
Comments and Suggestions for Authors
I read through your paper very carefully, and it presents some interesting considerations and contributions. First of all, I found the focal research objective based on your study very interesting given the relevance of the sector in terms of environmental issues. Thus, the analysis of efforts made in this field is commendable and deserves further investigation. However, some considerations and suggestions should be highlighted.
[Response]: We really appreciate your comments.
Comment [1] First of all, I'd have appreciated more depth from the literature background analysis.
[Response]: Thank you for your comment. We have revised and improved the analyzation of literature background in the third paragraph of 1. Introduction. Details are shown as flows:
“Recently, several studies have focused on the evaluation of agricultural systems with energy, economic, and environmental analysis [11–13]. Energy is a vital input during crop production and energy efficiency is an important factor for the sustainable assessment of an agricultural system [14–15]. Economic analysis, assessing the cost and income of a studied system, is a vital index that cannot be neglected to promote the sustainable agricultural production [16–17]. Additionally, agricultural activities are an important source of GHG emissions and exceed 24% of the total global GHG emissions [18]. Hence, optimization of agricultural systems has been identified as an attractive mitigation strategy [19–21]. To date, extensive studies have been done to assess the energy, economic or environmental performance of single crop cultivation systems e.g., rice [13], maize [22], wheat [23], potato (Solanum tuberosum L.) [24], sweet sorghum (Sorghum bicolor L.) [25], Jerusalem artichoke (Helianthus tuberosus L.) [16] and sweet potato [26]. Previous studies have also compared and analyzed different cropping systems from the perspectives of energy, economy, and environment. For instance, Soni et al. [27] evaluated the energy performance of two rice-based cropping systems in the middle Indo-Gangetic plains of India. Yang et al. [28] found that diversified cropping systems including grain, forage, and bioenergy crops can effectively reduce the carbon footprint in the North China plain based on a life-cycle assessment (LCA) estimation. Li et al. [29] reported the economic, energy and environmental consequences of shifting from maize-wheat to forage rotation in the North China Plain. However, few studies have addressed the energy, economic, and environmental performance of diversified sweet potato-based cropping systems. Rationalization of sweet potato-based cropping systems should be done by evaluating the indicators of green and circular economies, such as high-energy efficiency and economic productivity, as well as low GHG emissions.”. (Page 2 in the revised manuscript)
Comment [2] Secondly, I'd explain better the relevance of the selected region and whether the analysis could be replicated in others too.
[Response]: Yes, we have revised the explanation for the selected region in the fourth paragraph of section 1. Introduction:
“Guangdong, a province in South China, was selected as a case study to evaluate the life-cycle energy, economic, and environmental impacts of diversified sweet potato-based cropping systems. Firstly, Guangdong is a representative province of intensive sweet potato production, with an annual production of 3.5 million tons [30]. Secondly, Guangdong is endowed with special climate conditions involving abundant solar radiation and water resources, which create extremely favorable conditions for the multi-cropping.” (Page 2 in the revised manuscript)
In addition, we added a sentence in the section of 5. Conclusions as “Secondly, the sustainable development assessment framework of agricultural cropping systems in this study could be used in other crops or countries” (Page 13 in the revised manuscript)
Comment [3] Further on, I suggest enlarging the conclusion section in order to highlight the potential of the paper, its contribution as well as future developments.
[Response]: We accepted and revised the section of 5. Conclusions as:
“This study assessed and compared the energy consumption, economic benefit, and GHG emissions of five sweet potato-based cropping systems in South China. In conclusion, double cropping systems (i.e., SPSP, SPRI, SPMA, and SPPO) proved more conducive to ensure food security because crops yield under these systems are higher than that of monoculture (SP). For double cropping systems, in detail, continuous cultivation of sweet potato (SPSP) exhibited obvious advantages in energy efficiency, net return, and eco-efficiency. The SPMA system exhibited the highest net energy and energy rate, while the SPRI had a low level of GHG emissions. Even though each double cropping system has its advantages and there will be a balance when selecting the sweet potato-based cropping system. However, in general, appropriately designed, and extended rotations involving a greater number of crops (e.g., sweet potato, maize, and rice) can effectively reduce the GHG emissions while maintaining or even increasing the systems productivity”.
“The result of this study firstly provides the reference information for policy makers to optimize the diversified cropping systems for sustainable development of agriculture in South China. Secondly, the sustainable development assessment framework of agricultural cropping systems in this study could be used in other crops or countries. Furthermore, non-GHG environmental considerations and the impact of farm size and region conditions on diversified cropping systems are important directions for future research.”. (Page 13 in the revised manuscript)
Comment [4] The paper is relevant and I believe that - if implemented - it could represent a boost in LCA literature.
[Response]: Thank you very much.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors
The paper focuses on a life cycle analysis of different sweet potato-based cropping systems carried out in the South of China. The topic appears in line with the aims and scopes of the journal so it could be considered for publication. Anyhow, some amendments should be done in order to make it suitable for publication.
Please consider the suggestion below:
Title
In the title “environmental performance” is indicated but in the reality the paper face only the GHG emissions. I suggest changing the title in order to better point out the real focus of the analysis.
Abstract
According to the guidelines of the Journal (and considering the limit of 200 words), I suggest inserting in the abstract some sentences about methodology.
Introduction
This section should be improved, more references should be added especially concerning previous studies about life cycle assessment applied to different cropping systems.
In line 54 only two studies are cited (too few). Please enhance the overview about carbon balance, too.
Material and Methods
I suggest inserting the questionnaire in the supplementary material.
More information about data calculation should be given (e.g. I am not able to find in the text if the calculation of energy referred to fertilizers includes also their application, I also checked the reference in supplementary materials but “Luo et al.” is only in Chinese).
What about data quality? How do the authors face the problem of uncertainty?
Tables about data should be moved from the section Results to Material and Methods.
In order to understand the real sustainability of the systems, It could be useful to add a table in which data per hectare are divided per SPEY.
Results
I suggest better arranging this section. As above mentioned, some tables could be moved in the previous section (those about input data).
I suggest changing the colour of figure 4 (water for irrigation looks to have the same color of plastic film)
As suggested for data presentation, figures in which the results are referred to SPEY should be added in order to make the cropping systems really comparable.
Conclusion
The conclusion should be reinforced by adding more consideration to future perspectives of the analysis and their application to other cropping systems.
Author Response
Comments and Suggestions for Authors
The paper focuses on a life cycle analysis of different sweet potato-based cropping systems carried out in the South of China. The topic appears in line with the aims and scopes of the journal so it could be considered for publication. Anyhow, some amendments should be done in order to make it suitable for publication.
[Response]: We really appreciated the comments. We have revised the manuscript according to your comments accordingly.
Title:
Comment [1] In the title “environmental performance” is indicated but in the reality the paper face only the GHG emissions. I suggest changing the title in order to better point out the real focus of the analysis.
[Response]: We agreed and revised the title as “Life-Cycle Energy, Economic, and Greenhouse Gas Emissions of Diversified Sweet Potato-Based Cropping Systems in South China”. (Page 1 in the revised manuscript)
Abstract:
Comment [2] According to the guidelines of the Journal (and considering the limit of 200 words), I suggest inserting in the abstract some sentences about methodology.
[Response]: We agreed and added the sentences as “Therefore, the comprehensive assessment of diversified sweet potato-based cropping systems (i.e., sweet potato monoculture (SP), continuous sweet potato cropping (SPSP), sweet potato–rice (SPRI), sweet potato–maize (SPMA), and sweet potato–potato (SPPO)) in South China was conducted with field survey and life-cycle assessment. The data were collected quantitatively using a questionnaire for face-to-face interviewing of 70 farmers.” (Page 1 in the revised manuscript)
Introduction
Comment [3] This section should be improved, more references should be added especially concerning previous studies about life cycle assessment applied to different cropping systems.
[Response]: We agreed and revised the third paragraph of 1. Introduction as follows:
“Recently, several studies have focused on the evaluation of agricultural systems with energy, economic, and environmental analysis [11–13]. Energy is a vital input during crop production and energy efficiency is an important factor for the sustainable assessment of an agricultural system [14–15]. Economic analysis, assessing the cost and income of a studied system, is a vital index that cannot be neglected to promote the sustainable agricultural production [16–17]. Additionally, agricultural activities are an important source of GHG emissions and exceed 24% of the total global GHG emissions [18]. Hence, optimization of agricultural systems has been identified as an attractive mitigation strategy [19–21]. To date, extensive studies have been done to assess the energy, economic or environmental performance of single crop cultivation systems e.g., rice [13], maize [22], wheat [23], potato (Solanum tuberosum L.) [24], sweet sorghum (Sorghum bicolor L.) [25], Jerusalem artichoke (Helianthus tuberosus L.) [16] and sweet potato [26]. Previous studies have also compared and analyzed different cropping systems from the perspectives of energy, economy, and environment. For instance, Soni et al. [27] evaluated the energy performance of two rice-based cropping systems in the middle Indo-Gangetic plains of India. Yang et al. [28] found that diversified cropping systems including grain, forage, and bioenergy crops can effectively reduce the carbon footprint in the North China plain based on a life-cycle assessment (LCA) estimation. Li et al. [29] reported the economic, energy and environmental consequences of shifting from maize-wheat to forage rotation in the North China Plain. However, few studies have addressed the energy, economic, and environmental performance of diversified sweet potato-based cropping systems. Rationalization of sweet potato-based cropping systems should be done by evaluating the indicators of green and circular economies, such as high-energy efficiency and economic productivity, as well as low GHG emissions.”. (Page 2 in the revised manuscript)
Comment [4] In line 54 only two studies are cited (too few). Please enhance the overview about carbon balance, too.
[Response]: We agreed and added three references related to carbon balance or greenhouse gas emissions in the third paragraph of 1. Introduction as follows:
- Huang, W., Wu, F., Han, W., Li, Q., Han, Y., Wang, G., Feng, L., Li, X., Yang, B., Lei, Y., Fan, Z., Xiong, S., Xin, M., 2022. Carbon footprint of cotton production in China: Composition, spatiotemporal changes and driving factors. Science of the Total Environment 821, 153407.
- Tang, C., Lu, Y., Jiang, B., Chen, J., Mo, X., Yang, Y., Wang, Z., 2022. Energy, economic, and environmental assessment of sweet potato production on plantations of various sizes in South China. Agronomy 12, 1290.
- Li, S., Wu, J., Ma, L., 2021. Economic, energy and environmental consequences of shifting from maize-wheat to forage rotation in the North China Plain. Journal of Cleaner Production 328, 129670.
Additionally, we revised this paragraph as follows:
“Recently, several studies have focused on the evaluation of agricultural systems with energy, economic, and environmental analysis [11–13]. Energy is a vital input during crop production and energy efficiency is an important factor for the sustainable assessment of an agricultural system [14–15]. Economic analysis, assessing the cost and income of a studied system, is a vital index that cannot be neglected to promote the sustainable agricultural production [16–17]. Additionally, agricultural activities are an important source of GHG emissions and exceed 24% of the total global GHG emissions [18]. Hence, optimization of agricultural systems has been identified as an attractive mitigation strategy [19–21]. To date, extensive studies have been done to assess the energy, economic or environmental performance of single crop cultivation systems e.g., rice [13], maize [22], wheat [23], potato (Solanum tuberosum L.) [24], sweet sorghum (Sorghum bicolor L.) [25], Jerusalem artichoke (Helianthus tuberosus L.) [16] and sweet potato [26]. Previous studies have also compared and analyzed different cropping systems from the perspectives of energy, economy, and environment. For instance, Soni et al. [27] evaluated the energy performance of two rice-based cropping systems in the middle Indo-Gangetic plains of India. Yang et al. [28] found that diversified cropping systems including grain, forage, and bioenergy crops can effectively reduce the carbon footprint in the North China plain based on a life-cycle assessment (LCA) estimation. Li et al. [29] reported the economic, energy and environmental consequences of shifting from maize-wheat to forage rotation in the North China Plain. However, few studies have addressed the energy, economic, and environmental performance of diversified sweet potato-based cropping systems. Rationalization of sweet potato-based cropping systems should be done by evaluating the indicators of green and circular economies, such as high-energy efficiency and economic productivity, as well as low GHG emissions.” (Page 2 in the revised manuscript)
Materials and Methods
Comment [5] I suggest inserting the questionnaire in the supplementary material.
[Response]: We agreed and added the questionnaire into supplementary material.
Comment [6] More information about data calculation should be given (e.g. I am not able to find in the text if the calculation of energy referred to fertilizers includes also their application, I also checked the reference in supplementary materials but “Luo et al.” is only in Chinese).
[Response]: We agreed and added the sentences in the revised manuscript as follows:
“Energy inputs of each cropping system included labor, machinery, diesel, fertilizers, pesticides, irrigation water, plastic film, and seeds. Energy outputs consisted of crops yield (main product) and aboveground biomass (by-product). Because the inputs and outputs of energy were measured in different units, the data were converted into a common energy unit through appropriate coefficients of energy equivalence (Table S1).”. (Page 5 in the revised manuscript)
Additionally, Table 2 in the revised manuscript presented the input and output data of five cropping systems. Energy equivalent of inputs and outputs were shown in Table S1. Formula 2-6 indicated the corresponding calculation information.
Comment [7] What about data quality? How do the authors face the problem of uncertainty?
[Response]: We added the sentences in the 2.1. Survey sites and data collection as “To ensure the quality and reliability of survey data, we firstly invited the leader of each village and introduced the significance of this study for agricultural sustainable development. Secondly, the leaders organized the farmers to fill out the questionnaires. Thirdly, the collected and uncertainty data was carefully verified by experts and experience. (Page 3 in the revised manuscript)
Comment [8] Tables about data should be moved from the section Results to Material and Methods.
[Response]: We agreed and moved the Table 2 in the original manuscript from 3. Results to 2. Material and Methods as Table 1 in the revised manuscript. (Page 4 in the revised manuscript)
Comment [9] In order to understand the real sustainability of the systems, It could be useful to add a table in which data per hectare are divided per SPEY.
[Response]: We really appreciate this comment. However, we didn’t add a table about SPEY in the revised manuscript because the data related to SPEY have been indicated in Figure 3, Table 3, and Table 4. Additionally, Figure 3 have been revised to present the results related to SPEY clearly in the revised manuscript. (Page 7-10 in the revised manuscript)
Results:
Comment [10] I suggest better arranging this section. As above mentioned, some tables could be moved in the previous section (those about input data).
[Response]: We agreed and moved the Table 2 in the original manuscript from 3. Results to 2. Material and Methods in the revised manuscript. (Page 4 in the revised manuscript)
Comment [11] I suggest changing the colour of figure 4 (water for irrigation looks to have the same color of plastic film)
[Response]: We agreed and changed the color of plastic film in Figure 4 in the revised manuscript. (Page 8 in the revised manuscript)
Comment [12] As suggested for data presentation, figures in which the results are referred to SPEY should be added in order to make the cropping systems really comparable.
[Response]: We agreed and modified Figure 3 to show the results related to SPEY clearly. (Page 7 in the revised manuscript)
Conclusion:
Comment [13] The conclusion should be reinforced by adding more consideration to future perspectives of the analysis and their application to other cropping systems.
[Response]: We agreed and added contribution of this study and future research of the analysis in the conclusion as follows:
“The result of this study firstly provides the reference information for policy makers to optimize the diversified cropping systems for sustainable development of agriculture in South China. Secondly, the sustainable development assessment framework of agricultural cropping systems in this study could be used in other crops or countries. Furthermore, non-GHG environmental considerations and the impact of farm size and region conditions on diversified cropping systems are important directions for future research.” (Page 13 in the revised manuscript)
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Dear Authors,
From my point of view, the paper you revised is now suitable for publication in its present form.
Regards
