Closing Yield Gaps through Soil Improvement for Maize Production in Coastal Saline Soil

Round 1

Reviewer 1 Report

Review of manuscript (596563): Closing yield gaps through soil improvement for maize production in coastal saline soil

 

 

The publication presented for review is very interesting. It was correctly written in terms of content, methodology and editorial content.
I propose to the authors of the publication minor corrections to improve it. I recommend publication for printing in the journal Agronomy.
I made notes in the yellow windows on the PDF publication.

 

 

Line 21 -  add - high or low pH?

Line 27 -  maybe better C-org

Line 28 – better calcium

Line 40 - enter the organic content from to, or average

Line 44 - give the full name of sodium

Line 75 – correct for – ratio

Line 94 - give a description of the X-axis:V6, V6-VT, VT-R6

Line 105-107 - enter the name of the growing phase in brackets

Line 120 - correct of accumulation to content

Line 245 – better C-org. - or SOC

Comments for author File: Comments.pdf

Author Response

Reviewer 1

Line 21 -  add - high or low pH?

Thank you for your comment. We agreed with the comment and added high pH in line 21.

Line 27 -  maybe better C-org

We agreed with the comment and added the abbreviation (SOC) of soil organic carbon in line 27 to achieve full text uniformity.

Line 28 – better calcium

Addressed. Yes, you are right. We changed the Ca into calcium in line 28.

Line 40 - enter the organic content from to, or average

Addressed. Yes, you are right. We added the soil organic carbon content (averaged 6.09 g kg^-1) in line 40.

Line 44 - give the full name of sodium

Addressed. Yes, you are right. We changed the Na into sodium in line 44.

Line 75 – correct for – ratio

Addressed. Yes, you are right. We changed the radio into ratio in line 76.

Line 94 - give a description of the X-axis:V6, V6-VT, VT-R6

Thank you for your comment. We added the description of the X-axis:V6, V6-VT, VT-R6 in line 96-97.

Line 105-107 - enter the name of the growing phase in brackets

Thank you for your comment. We added the name of the growing phase in brackets. (line 105-109)

Line 120 - correct of accumulation to content

Addressed. Yes, you are right. We changed the accumulation into content in line 111-122.

Line 245 – better C-org. - or SOC

Addressed. Yes, you are right. We changed the organic carbon into SOC in line 252.

Author Response File: Author Response.doc

Reviewer 2 Report

Dear Colleagues! I positively evaluate your experimental work and recommend it for publication with minor corrections:

Material and methods are usually placed at the beginning of the manuscript, and not at the end. The electrical conductivity of the soil solution is highly dependent on soil moisture (salt concentration), for example, see (DOI: 10.1134 / S1064229318120128). Guidelines are not designed for soil: water extraction 1: 1, but for the SATURATED STATE OF SOIL. After saturation with water, the soil is pressed or centrifuged, and then the conductivity is determined. It is for these conditions that the following guidelines (dS/m) were developed at the US Salinity Laboratory: 4–8 weak salinity; 8–16 moderate salinity; 16–32 high salinity; > 32 very high salinity. In your case, another analysis was used. Therefore, either give the guidelines by which you rated your salinity levels as “low” and “medium”. Or count on the well-known in the literature, using the dilution law (DOI: 10.1134 / S1064229318120128). For example, if you know the soil bulk density (D in g/cm3), it is easy to calculate approximately saturation moisture: Ws% = (100 /D – 100/2.62, where 2.62 g/cm3 is density of clay minerals in your soil). Extraction 1:1 ratio of soil to water is approximately equal to the water content: W%=100*1/1=100%. Then you can evaluate the conductivity in a saturated state, using the law of dilution: ECs =EC*W/Ws. For example, if your soil had bulk density of 1.4 g/cm3, Ws=100/1.4–100/2.62=33%. Then your assessment 4 sS/m will give a real value at saturation: ECs=4*100/33=12 dS/m or moderate salinity. A score of 6 dS/m will really ECs=6*100/33=18 dS/m or high salinity, in accordance with international guidelines of the US Salinity Lab. As you can see, the method you use can greatly underestimate the salinity of the soil. Most likely, it is precisely the high soil salinity  plus irrigation with the highly mineralized waters of the Yellow River that limits maize to realize its potential productivity. 15 Mg/ha FGDG and 7.5 Mg/ha FR it's not small doses. Please indicate, at least according to literature, the content of toxic elements in FGDG, especially strontium. Is there a risk of soil contamination when using this technology?

I hope that you will take into account all these comments and be able to quickly prepare the manuscript for publication.

 

Sincerely, Your Reviewer

Author Response

Material and methods are usually placed at the beginning of the manuscript, and not at the end.

Thank you for your comment. But “Agronomy” journal requires that materials and methods should be placed behind discussion in accordance with the manuscript submission overview.

The electrical conductivity of the soil solution is highly dependent on soil moisture (salt concentration), for example, see (DOI: 10.1134 / S1064229318120128). Guidelines are not designed for soil: water extraction 1: 1, but for the SATURATED STATE OF SOIL. After saturation with water, the soil is pressed or centrifuged, and then the conductivity is determined. It is for these conditions that the following guidelines (dS/m) were developed at the US Salinity Laboratory: 4–8 weak salinity; 8–16 moderate salinity; 16–32 high salinity; > 32 very high salinity. In your case, another analysis was used. Therefore, either give the guidelines by which you rated your salinity levels as “low” and “medium”. Or count on the well-known in the literature, using the dilution law (DOI: 10.1134 / S1064229318120128). For example, if you know the soil bulk density (D in g/cm3), it is easy to calculate approximately saturation moisture: Ws% = (100 /D – 100/2.62, where 2.62 g/cm3 is density of clay minerals in your soil). Extraction 1:1 ratio of soil to water is approximately equal to the water content: W%=100*1/1=100%. Then you can evaluate the conductivity in a saturated state, using the law of dilution: ECs =EC*W/Ws. For example, if your soil had bulk density of 1.4 g/cm3, Ws=100/1.4–100/2.62=33%. Then your assessment 4 sS/m will give a real value at saturation: ECs=4*100/33=12 dS/m or moderate salinity. A score of 6 dS/m will really ECs=6*100/33=18 dS/m or high salinity, in accordance with international guidelines of the US Salinity Lab. As you can see, the method you use can greatly underestimate the salinity of the soil. Most likely, it is precisely the high soil salinity plus irrigation with the highly mineralized waters of the Yellow River that limits maize to realize its potential productivity.

Addressed. Yes, you are right. Thank you very much for your comment. The bulk density was 1.47 and 1.55 g cm^-3 for two sites at the 0-20 cm soil layer in this study, respectively, which we had added to the manuscript. We calculated the ECe of 13.4 and 22.8 dS m^-1in accordance with the dilution law (DOI: 10.1134 / S1064229318120128). According to international guidelines of the US Salinity Lab, two sites in our study were moderate and high salinity levels. So we have revised the low and moderate salinity into the moderate and high salinity in the new manuscript.

15 Mg/ha FGDG and 7.5 Mg/ha FR it's not small doses. Please indicate, at least according to literature, the content of toxic elements in FGDG, especially strontium. Is there a risk of soil contamination when using this technology?

Thank you for your comment. The rate of application for FGDG used in the text was based on Rhoton and McChesney (2011) and Wang et al. (2012), and calculation of the gypsum requirement (Rasouli et al., 2013) which showed that the amendment effect with rate of application for FGDG (about 15 Mg ha^-1) was better. The dosage of FR in this study was determined in accordance with the previous studies (Wang et al., 2014).

This is a very important message for us to calculate the content of toxic elements in FGDG, because of the application of big doses. Although some studies showed that the massive of FGDG and FR did not result in soil contamination in short or long term measurement (Wang and Yang, 2018, Zhao et al., 2016), it is a pity that a risk of soil contamination is not paid attention in this paper. So we should further research on risk of soil contamination when using this technology in future research. Thank you again for your comments.

 

Rhoton, F.E., and D.S. McChesney. Erodibility of a sodic soil amended with flue gas desulfurization gypsum. Soil Sci. 2011,176:190-195.

Wang, J., Z. Bai, and P. Yang. Sodic soil properties and sunflower growth as affected by byproducts of flue gas desulfurization 2012, 7:e52437.

Rasouli, F., A. K. Pouya, and N. Karimian. Wheat yield and physico-chemical properties of a sodic soil from semi-arid area of Iran as affected by applied gypsum. Geoderma. 2013, 193-194: 246-255.

Wang, L.; Sun, X.; Li, S.; Zhang, T.; Zhang, W.; Zhai, P. Application of organic amendments to a coastal saline soil in north China: effects on soil physical and chemical properties and tree growth. PLoS One. 2014, 9, e89185.

Wang, J.; Yang, P. Potential flue gas desulfurization gypsum utilization in agriculture: A comprehensive review. Renew. Sust. Energ. Rev. 2018, 82, 1969-1978.

Zhao, Y.; Yan, Z.; Qin, J.; Ma, Z.; Zhang, Y.; Zhang, L. The potential of residues of furfural and biogas as calcareous soil amendments for corn seed production. Environ. Sci. Pollut. R. 2016, 23, 6217-6226.

Author Response File: Author Response.doc