Does Land Operation Scale Improve Rice Carbon Emission Productivity? Evidence from 916 Farmers in Guangdong Province, China
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsOverall Assessment
This study examines the impact of land operation scale on rice carbon emission productivity and intensity using micro-survey data from 916 rice farmers in Guangdong Province. The research aligns with China’s dual goals of agricultural decarbonization and food security. While the empirical methodology is generally sound and data collection is rigorous, major revisions are required before publication, as outlined below.
Major Comments
1. Sample Representativeness Issues
The skewed sample distribution undermines the reliability of the inferred U-shaped relationship. Table 2 shows that 90% of sampled farms operate ≤1 ha, with only 5 households (0.55%) exceeding 1.5 ha. The right segment of the U-curve, where scale expansion increases emissions, lacks statistical robustness due to insufficient large-scale samples ,n = 5, introducing small-sample bias risks.
2. Unverified Theoretical Mechanisms
The hypothesis that "scale expansion promotes technology adoption" fails empirical validation. The study neither analyzes correlations between operational scale and technology adoption rates, nor tests mediating effects of these variables in the "scale–emission" relationship.
3. Vague Policy Implications
（1）The U-shaped relationship is identified, but no optimal scale range is quantified.
（2）Regional “scale–emission” differences are reported but not explained or leveraged for policy.
（3）Recommendations like "avoid excessive concentrations in rice paddies" remain ambiguous due to undefined thresholds, diminishing practical relevance.
Minor Comments
1. Incorrect units: (e.g., "kgCO₂eq·ha⁻²" in the abstract/text) must be corrected to ha⁻¹.
2. The author introduces many new terms but doesn’t define them clearly, such as “indirect carbon emission productivity”.
3. Update literature to include key studies from the last five years.
Author Response
Dear reviewer,
Thank you very much for your comments and professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have try our best to make corrected modifications on this revised manuscript. We hope that our work can be improved. Furthermore, we would like to show the details as follows:
Reviewer 1 Report
This study examines the impact of land operation scale on rice carbon emission productivity and intensity using micro-survey data from 916 rice farmers in Guangdong Province. The research aligns with China’s dual goals of agricultural decarbonization and food security. While the empirical methodology is generally sound and data collection is rigorous, major revisions are required before publication, as outlined below.
Major Comments
- Sample Representativeness Issues
The skewed sample distribution undermines the reliability of the inferred U-shaped relationship. Table 2 shows that 90% of sampled farms operate ≤1 ha, with only 5 households (0.55%) exceeding 1.5 ha. The right segment of the U-curve, where scale expansion increases emissions, lacks statistical robustness due to insufficient large-scale samples, n=5, introducing small-sample bias risks.
- Unverified Theoretical Mechanisms
The hypothesis that "scale expansion promotes technology adoption" fails empirical validation. The study neither analyzes correlations between operational scale and technology adoption rates, nor tests mediating effects of these variables in the "scale–emission" relationship.
- Vague Policy Implications
(1) The U-shaped relationship is identified, but no optimal scale range is quantified.
(2) Regional “scale–emission” differences are reported but not explained or leveraged for policy.
(3) Recommendations like "avoid excessive concentrations in rice paddies" remain ambiguous due to undefined thresholds, diminishing practical relevance.
Minor Comments
- Incorrect units: (e.g., "kgCO₂eq·ha⁻²" in the abstract/text) must be corrected to ha⁻¹.
- The author introduces many new terms but doesn’t define them clearly, such as “indirect carbon emission productivity”.
- Update literature to include key studies from the last five years.
Author response
Comment 1: The skewed sample distribution undermines the reliability of the inferred U-shaped relationship. Table 2 shows that 90% of sampled farms operate ≤1 ha, with only 5 households (0.55%) exceeding 1.5 ha. The right segment of the U-curve, where scale expansion increases emissions, lacks statistical robustness due to insufficient large-scale samples, n=5, introducing small-sample bias risks.
Authors’ Response: Thank you for pointing out. In the sample, 73 households operated more than 1 ha, of which 31 households operated more than 2 ha (more detailed data distribution has been given in the Table 2, Line 201). Because the rural land in China does not belong to individuals, it is village collective ownership, which leads to widespread small-scale land operation. The sampling results accord with the reality and are also the background of the research problem.
Comment 2: The hypothesis that "scale expansion promotes technology adoption" fails empirical validation. The study neither analyzes correlations between operational scale and technology adoption rates, nor tests mediating effects of these variables in the "scale–emission" relationship.
Authors’ Response: Due to the limitations of the survey questionnaire data, we are not able to test the hypotheses related to technology adoption in this paper, which would be our next paper that requires further research in the future. Further, we had added information about low-carbon technologies in the discussion section (Lines 425-428).
Comment 3.1: The U-shaped relationship is identified, but no optimal scale range is quantified.
Authors’ Response: According to the data calculation (Model 10 in Table 7, Line 371), the inflection point for reducing the carbon emission intensity of production by expanding the land operation scale of rice farmers is 10.68 ha (Line 360). That is, when the operation scale of rice farmers is less than 10.68 ha, increasing the scale can reduce the carbon emission intensity. However, when the operation scale exceeds 10.68 ha, increasing the scale will instead increase the carbon emission intensity.
Comment 3.2: Regional “scale–emission” differences are reported but not explained or leveraged for policy.
Authors’ Response: We have added a detailed explanation of the inter-regional carbon emission differences in 3.1 (Lines 315-325), and the specific content is as follows: Variations in carbon emission intensity across Guangdong Province's four regions primarily arise from fertilizer application rates. The northern region, characterized by mountainous and hilly terrain with low soil fertility and limited fertilizer retention, experiences lower average temperatures. Consequently, it applies the most chemical fertilizers to support rice growth. Conversely, the Pearl River Delta, with more favorable soil fertility and climate for rice production, practices high multiple cropping, including double or triple-cropping rice, which necessitates substantial fertilizer use and results in high carbon emission intensity. In contrast, the western and eastern regions, benefiting from warmer climates and moderate soil fertility, apply less fertilizer, resulting in lower carbon emission intensity. We also added relevant recommendation in Section 5 (Lines 457-460), and the content is as follows: In the context of Guangdong Province, policy interventions should prioritize the northern Guangdong and PR Delta regions, as these exhibit relatively higher carbon emission intensities associated with rice production.
Comment 3.3: Recommendations like "avoid excessive concentrations in rice paddies" remain ambiguous due to undefined thresholds, diminishing practical relevance.
Authors’ Response: The content of relevant policy recommendations has been revised (Lines 456-457), and the specific content is: It should be notice that the optimal operational scale for rice production to minimize carbon emission intensity is below 10 ha.
Comment 4: Incorrect units: (e.g., "kgCO₂eq·ha⁻²" in the abstract/text) must be corrected to ha⁻¹.
Authors’ Response: Thank you for pointing out. We have been revised relevant units.
Comment 5: The author introduces many new terms but doesn’t define them clearly, such as “indirect carbon emission productivity”
Authors’ Response: Thank you for pointing out. We had provided an explanation for the "indirect carbon emission productivity" in the footnote on page 7. The specific content is as follows: Indirect carbon emission productivity is a component of overall carbon emission productivity. Rice production indirect carbon emission productivity pertains to emissions not originating from paddy soil emission in rice production (refer to Figure 2, Table 3, Equation 1, and Equation 3 for details). Equation 4 calculates the rice yield indirect carbon emission productivity, while Equation 5 determines the rice yield value indirect carbon emission productivity.
Comment 6: Update literature to include key studies from the last five years.
Authors’ Response: We had updated some new reference as follows:
Ren, C.; Liu, S.; Grinsven, H. et al. The impact of farm size on agricultural sustainability. Journal of Cleaner Production 2019, 220, 357–367.
Xu, X.; Zhou, Z.; Sun, M. et al. Dual growth of green total factor productivity and greenhouse gas emission intensity of smallholder farms in China: Trends and misallocation. Resources, Conservation & Recycling 2025, 222, 108421.
Yu, Y.; Hu, Y.; Gu, B. et al. Reforming smallholder farms to mitigate agricultural pollution. Environmental Science and Pollution Research 2022, 29, 13869–13880.
Xiong, C.; Wang, G.; Su, W. et al. Selecting low-carbon technologies and measures for high agricultural carbon productivity in Taihu Lake Basin, China. Environmental Science and Pollution Research 2021, 28, 49913–49920.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript explores an important research question by employing farmers' input-output data from their rice paddy operations to assess carbon emission productivity and intensity associated with rice production on an individual basis. It further investigates how the scale of land operation influences both carbon emission productivity and intensity. However, the introduction lacks clarity, and the literature review does not adequately identify existing research gaps, particularly regarding carbon density measured with macro-level data and carbon emission productivity in paddy rice farming. Additionally, the Materials and Methods section is significantly lacking in practical elements, especially in its description of the study area and the absence of a map illustrating the locations of the farms under investigation. The Discussion section requires a more comprehensive analysis of the key findings, specifically regarding how the scale of operations can enhance indirect carbon emission productivity, as well as the vital role of expanding operational scale among individual farmers to improve carbon emission productivity.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsI have some doubts and few questions.
- What farm size is considered in China small – medium – large? Maximum in the sample is 4,667 hectares (table 4), but on page 12 (row 390) the authors refer to 15-40 range of an optimal carbon productivity. What is the structure?
- Following on the above. Farms in the sample were selected in one or two counties of the province (row 92)? It should be decided which version is true. More important is the structure of the farming sector in the Guangdong province. If similar to the sample than conclusions are valid for the province, otherwise models are representative only for population such as in the sample.
- Point 2 indicates the problem of the paper – estimations are done for the specific sample, but the proof for the Hypothesis 2 is based on the literature. This must be sorted out and clarified.
- Paddy emissions (75%) are beyond control so the main source of CO2 reductions is fertilization. Row 149 suggests “adopting relevant technologies”. What are they in practice?
- Rows 154 – 155. Is management really “less precise” with the size increase within the range 0,0067 – 4,667 hectares?
- It seems not necessary to include emissions from labor. Savings are problematic and human being generate emissions whatever they do.
- Figure 3 – hard no notice any differences.
- R-squared is very small. Does it mean variables that might make a difference were not identified, or rather the possibility of mitigating emissions within the range of sizes in the sample is nearly zero?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsNo more comments
