High Maize Density Alleviates the Inhibitory Effect of Soil Nitrogen on Intercropped Pea
, Wen Yin 1,2, Falong Hu 1,2, Aizhong Yu 1,2, Hong Fan 1,2 and Qiang Chai 1,2,*Round 1
Reviewer 1 Report
In the manuscript High maize density alleviates the inhibitory effect of soil nitrogen on intercropped pea by Cai Zhao and collaborators, the authors study cropping patterns to develop sustainable agroecosystems. This manuscript is written in concise way and quite easy to read when to forget all the missing spaces in very many places (lines 76, 88, 122, 199, 201, 207, etc.) and the repetitions of “before planting” in line 102.
Why it is important to irrigate just before soil freezing (see line 107)? What kind of irrigation water was used?
Have you also evaluated the effect of nitrogen leaching and nitrous oxide (N2O) emission? In addition, how much nitrogen may have been lost from the system due to N2 emission? At least, it is reasonable to add relevant text regarding these matters with references.
Ca is not the best abbreviation for the relative change ratio as it means also calcium. If possible, it may be reasonable to change it.
What smoothing was used to draw the lines in Figure 2?
Some parts seem to be missing in the end of manuscript. Titles without any content: 6. Patents; Supplementary Materials; Author Contributions; Funding; Appendix A; Appendix B. Please delete them or fill these sections with relevant information.
Author Response
Response to the comments of the learned reviewers - 1
The comments have been reproduced in italics and response has been given below each comment.
In the manuscript High maize density alleviates the inhibitory effect of soil nitrogen on intercropped pea by Cai Zhao and collaborators, the authors study cropping patterns to develop sustainable agroecosystems. This manuscript is written in concise way and quite easy to read when to forget all the missing spaces in very many places (lines 76, 88, 122, 199, 201, 207, etc.) and the repetitions of “before planting” in line 102.
>>Thanks for the positive comments and suggestions. We corrected all the missing apace sentences and deleted the repetitions of “before planting” in line 106.
Why it is important to irrigate just before soil freezing (see line 107)? What kind of irrigation water was used?
>>Thanks for pointing this out. Because the mean annual precipitation is 155 mm at the experimental site, occurring mainly from June to September, and the potential evaporation is greater than 2400 mm, so irrigation before soil freezing is needed for crop seeding and emergence in the next year. The irrigation water is the groundwater.
Have you also evaluated the effect of nitrogen leaching and nitrous oxide (N2O) emission? In addition, how much nitrogen may have been lost from the system due to N2emission? At least, it is reasonable to add relevant text regarding these matters with references.
>>Thanks for pointing this out. The effect of nitrogen leaching, nitrous oxide (N2O) emission and the lost from the system due to N2 emission will be evaluated in our further work. We added the discussion in lines 242-244.
Ca is not the best abbreviation for the relative change ratio as it means also calcium. If possible, it may be reasonable to change it.
>>Thank you for your suggestion. We changed the Ca into Cis.
What smoothing was used to draw the lines in Figure 2?
>>Thanks for pointing this out. The spline was used to draw the lines in Origin for Figure 2.
Some parts seem to be missing at the end of the manuscript. Titles without any content: 6. Patents; Supplementary Materials; Author Contributions; Funding; Appendix A; Appendix B. Please delete them or fill these sections with relevant information.
>>Thanks for pointing this out. These titles (6. Patents; Supplementary Materials; Author Contributions; Funding; Appendix A; Appendix B.) may be automatically generated by the system, we delete the titles: 6. Patents; Supplementary Materials; Appendix A; Appendix B. and we added the content of Author Contributions.
Reviewer 2 Report
A Brief Summary: The manuscript titled “High maize density alleviates the inhibitory effect of soil nitrogen” provides significant and novel information on alleviation of inhibitory effect of soil N on nodulation of pea through modification in maize planting density in maize-pea intercropping. The study was conducted in the region where intercropping is considered over monoculture, therefore, the results from the study could be applied.
Broad Comments: The method section of the manuscript need to be improved by providing details about whether parameters over three years. The statistical analysis section need to be improved by stating whether year effect was significant or not and then results sections should be modified accordingly. The statements regarding main or interaction affects needs to be improved in the results section. The levels of significance should be provided wherever effects were observed significant and when describing in the results.
Specific Comments:
Line 82: In table 3, main plots consisted of three cropping patterns instead of four. Please clarify? “Monoculture maize with three different densities” is not mentioned in the cropping systems.
Line 106: Give some details about how the available soil moisture was measured and how supplemental irrigation amount was estimated to maintain optimum soil moisture and avoid any N leaching from over irrigating? What and how weather parameters were recorded at the study location during the experimental period? It’s would be good to provide table or graph for three years (2012-2014) rainfall and air temperature data along with long term (~ 10 years averaged) climatic data during growing season at the study location.
Line 113: In most field studies conducted in the past, row length of at least one meter was used for destructive harvesting and further analysis, which is considered a good representative sample for entire population. In this study, row length of 30 cm was used for destructive harvesting. It would be more appropriate to clarify if 30 cm row length was good representative sample to determine the N accumulation for the entire population by referring some past literature in the introduction section or providing average stand count obtained within 30 cm row length. It would be useful to provide intra-row spacing along with rate (see line 94) for pea to determine stand count within 30 cm of row length.
Line117: Provide reference for measuring aboveground N using high-induction 116 furnace C and N analyzer. Also, provide more details on procedure to analyze N such as how much sample was homogenized for N analysis?
Line 142: Since the means for each year were presented separately in this study which tell that “year” was also considered as fixed effect in the statistical analysis. Please clarify if year effect was significant or not. If year effect was not significant then data of three years should be pooled, otherwise the statistical analysis is correct. Further, results are presented as an averaged across years, so why the data and statistics presented for separate years (see line 148-151 and 163). Please clarify if year was significant or not in the study.
Line 147-151: Provide the level of significance (P- value) for observed increase in nodulation with intercropping compared to monoculture.
Line 152: What functions was used to fit the means observed across days after pea emergence? Since, days after pea emergence was not used as fixed effect in the statistical model, therefore, fitting any function to mean values observed across days after emergence or using line plot is irrelevant.
Line 176: Since, year had no effect on IEN on pea, so there is no point of providing data of IEN for three separate years (see Fig. 3).
Line 177: If there was interaction effect between cropping system and N fertilization, why the means are compared only for cropping system and within given Nitrogen levels. The statistics presented for IEN in Fig. 3 is one way analysis and does not tell whether a given cropping systems was significantly different between two levels of N or not? Please modify the “Nitrogen use efficiency of pea” section by providing the details of interaction effect between cropping system and N fertilization.
Line 178-179: No point of providing details of N fertilization effect if it was not significant.
Line 200: Change ViciafabaL. to Vicia faba L.
Line 206: add “with” after “consistent”
Line 207: Add space after bean
Line 207: Change VignaunguiculataL. to Vigna unguiculata L. Please check the scientific names throughout the manuscript.
Line 208: Change Glycine maxL. to Glycine max L. Add space before “Therefore”.
Line 208-209: Rewrite the sentence for clarity.
Line 219: add space before “for”
Line 270: use initial for first and middle name of authors.
Line 291: use initial for first and middle name of authors.
Check initials for first and middle name of authors in references- 19-29.
Author Response
Response to the comments of the learned reviewers -2
The comments have been reproduced in italics and response has been given below each comment.
Line 82: In table 3, main plots consisted of three cropping patterns instead of four. Please clarify? “Monoculture maize with three different densities” is not mentioned in the cropping systems.
>>Thanks for pointing this out. We corrected it in line 82, and added the monoculture maize densities in line 83-86.
Line 106: Give some details about how the available soil moisture was measured and how supplemental irrigation amount was estimated to maintain optimum soil moisture and avoid any N leaching from over irrigating? What and how weather parameters were recorded at the study location during the experimental period? It’s would be good to provide table or graph for three years (2012-2014) rainfall and air temperature data along with long term (~ 10 years averaged) climatic data during growing season at the study location.
>>Thank you for your suggestion. We added the irrigation method, irrigation system in lines 112-116.
Line 113: In most field studies conducted in the past, row length of at least one meter was used for destructive harvesting and further analysis, which is considered a good representative sample for entire population. In this study, row length of 30 cm was used for destructive harvesting. It would be more appropriate to clarify if 30 cm row length was good representative sample to determine the N accumulation for the entire population by referring some past literature in the introduction section or providing average stand count obtained within 30 cm row length. It would be useful to provide intra-row spacing along with rate (see line 94) for pea to determine stand count within 30 cm of row length.
>>Thanks for pointing this out. We are aware that destructive sampling, which removed an important number of maize and pea plants from the intercropped plots during the growing season, could have altered competitive interactions between maize and pea. So, 30-cm-long rows of pea (17 plants) were collected in this study. We added the density of pea in lines 83-85.
Line117: Provide reference for measuring aboveground N using high-induction 116 furnace C and N analyzer. Also, provide more details on procedure to analyze N such as how much sample was homogenized for N analysis?
>>Thank you for your suggestion. We added the reference and provide more details on procedure to analyze N in lines 126-130.
Line 142: Since the means for each year were presented separately in this study which tell that “year” was also considered as fixed effect in the statistical analysis. Please clarify if year effect was significant or not. If year effect was not significant then data of three years should be pooled, otherwise the statistical analysis is correct. Further, results are presented as an averaged across years, so why the data and statistics presented for separate years (see line 148-151 and 163). Please clarify if year was significant or not in the study.
>>Thank you for your suggestion. We rewrote this paragraph in lines 159-172.
Line 147-151: Provide the level of significance (P- value) for observed increase in nodulation with intercropping compared to monoculture.
>>Thank you for your suggestion. We added in line 159-172.
Line 152: What functions was used to fit the means observed across days after pea emergence? Since, days after pea emergence was not used as fixed effect in the statistical model, therefore, fitting any function to mean values observed across days after emergence or using line plot is irrelevant.
>>Thank you for your suggestion. We rewrote this paragraph in lines 159-172.
Line 176: Since, year had no effect on IEN on pea, so there is no point of providing data of IEN for three separate years (see Fig. 3).
>>Thank you for your suggestion. We think three years data is more reliable, and can consistent with previous results.
Line 177: If there was interaction effect between cropping system and N fertilization, why the means are compared only for cropping system and within given Nitrogen levels. The statistics presented for IEN in Fig. 3 is one way analysis and does not tell whether a given cropping systems was significantly different between two levels of N or not? Please modify the “Nitrogen use efficiency of pea” section by providing the details of interaction effect between cropping system and N fertilization.
>>Thanks for pointing this out. We added it in lines 199-201.
Line 178-179: No point of providing details of N fertilization effect if it was not significant.
>>Thank you for your suggestion. We deleted this sentence.
Line 200: Change ViciafabaL. to Vicia faba L.
>>Thank you for your suggestion. The correction is done in line 220.
Line 206: add “with” after “consistent”
>>Thanks for pointing this out. We added it in line 226.
Line 207: Add space after bean
>>Thanks for pointing this out. The correction is done in line 227.
Line 207: Change VignaunguiculataL. to Vigna unguiculata L. Please check the scientific names throughout the manuscript.
>>Thanks for pointing this out. The correction is done in line 227, and we checked the scientific names throughout the manuscript.
Line 208: Change Glycine maxL. to Glycine max L. Add space before “Therefore”.
>>Thanks for pointing this out. The correction is done in line 228.
Line 208-209: Rewrite the sentence for clarity.
>>Thank you for your suggestion. We changed the sentence in lines 228-230.
Line 219: add space before “for”
>>Thanks for pointing this out. The correction is done in line 239.
Line 270: use initial for first and middle name of authors.
>>Thanks for pointing this out. We changed it in line 292.
Line 291: use initial for first and middle name of authors.
>>Thanks for pointing this out. We changed it in line 312.
Check initials for the first and middle name of authors in references- 19-29.
>>Thank you for your suggestion. We checked and changed the initials for first and middle name of authors in references- 19-29.
