Rice Cultivar Renewal Reduces Methane Emissions by Improving Root Traits and Optimizing Photosynthetic Carbon Allocation
, Lu Chen 1,2,†, Xian Han 1, Kai Yang 1, Kun Liu 1, Jun Wang 1, Yun Chen 1,3 and Lijun Liu 1,*
Round 1
Reviewer 1 Report
Please see the comments in the attached file.
Comments for author File: 
Comments.pdf
Author Response
Response: Thank you very much for your positive comments on our manuscript. We have added the linear regression lines, r, R2, and P value in Fig. 2.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments
Manuscript sounds well from all angle and reduction of methane emission was quantified due to cultivar renewal from 1950 to 2010. I feel that atmoshpheric CO2 concentration increase in environment and change in production practices particularly N application from 1950 to 2010 might have also contributed along with cultivar renewal, which probably may be added, quantified separately by analysing the already known decade wise historical data. Presently , this looks that only breeding has contributed to increase in grain yield where as rice production and protection practices might have contributed equally, which is lacking in the study. To quantify these things, only some more statistical analysis is required.
Author Response
Response: Thank you very much for your positive comments on our manuscript. Based on your advice, we have added the changes of crop management and atmospheric CO2 concentrations and their effects on rice yield in the Discussion section:
In the past 60 years, the grain yield of rice in China has increased tripled, which could be attributed to the CR, improved crop management practices such as N fertilizer application, and plant protection practices (Peng et al., 2009). Some studies showed that the contribution of CR and crop management to yield increase reached 38.9%-61.7% and 9.3%-16%, respectively (Song et al., 2015; Yu et al., 2012). Since the 1990s, the N fertilizer input has reduced, but the grain yield of rice is still increasing, suggesting that the CR rather than N fertilizer is the main factor influencing the yield increase of rice in recent 20 years (Sun & Huang, 2012; Xin et al., 2012). The increasing atmospheric CO2 concentration also showed a fertilizer effect on rice growth since it acted as the substrate of plant photosynthesis. A meta-analysis showed that the increase of atmospheric CO2 concentration could increase the grain yield of rice by 12.7%-24.7%, showing the highest enhancement on hybrid rice but the lowest effect on japonica rice (Hu et al., 2021). Therefore, the increase in grain yield in the region where japonica rice was widely cultivated could be mainly attributed to CR. (Lines 333-345)
Author Response File: Author Response.pdf
