Spatial and Temporal Evolution of Sowing and the Onset of the Rainy Season in a Region of Large Agricultural Expansion in Brazil

Round 1

Reviewer 1 Report

The present manuscript provides a comprehensive assessment of the Western Bahia area in Brazil, including maps of sowing dates from 2001 to 2019 as well as the precipitation pattern and dates. The authors performed really effectively in both analysis and writing. Below are some small remarks and questions. Please pay close attention to the ground truth information. In order to enhance the comparison, it is recommended that more information be gathered regarding the sowing dates of non-irrigated fields, strengthening the comparison. 

 

1 Introduction: 

28: compared to which period? ; please use the complete name “soybean” across the document, and in this line include the scientific name, for this crop as well as the ones named in line 30. 

35: which crops? 

56: the irrigation is coming from the aquifer or surface waterbodies? 

78: the authors should remove the word “newest” since this product had been in use for decades. 

2 Materials and methods: 

 

2.1 Study area: 

Please include the area in km2 for WB and the average size for the fields in this territory. 

Figure 2: include the rivers and aquifer (Santos, A. B., Heil Costa, M., Chartuni Mantovani, E., Boninsenha, I., & Castro, M. (2020). A Remote Sensing Diagnosis of Water Use and Water Stress in a Region with Intense Irrigation Growth in Brazil. Remote Sensing, 12(22), 3725.)

 

 

2.4 Determination of swing dates from green-up dates 

Are those 59 pivots distributed across the area or concentrated in a close space? 59 fields, only for one category (irrigated) between 3 years is not a representative sample for ground truth comparison and validation. 

Regarding the irrigation platform, what information is extracted? what type of farmers are the ones using this platform? Technology adopters? This could contain a significant bias. 

 

2.5 Onset of the rainy season

Please check the equation number 

Was the CHIRPS product rescaled to 500m to match the MODIS resolution? 

 

 

3.Results 

 

Figure 4 and 6, use DOY instead of date dd/mm to keep consistency and make it easier to compare. 

 

4.5 Wrong number 

 

 

 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The topic is interesting and cutting edge, but the research design and analysis need a lot of improvement. The manuscript looks like an experiment report, with limited analysis, and I cannot find any useful, deep results.  

Some minor concerns, say, MATOPIBA, the authors introduced this acronym twice, one in the introduction, one in study area.

Western Bahia has 10 million ha rain-fed farmland, then how many areas dedicated to irrigated land?

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

General comments:

The manuscript presents a study on the relationship between crops sowing date and rainy season onset in a double cropping system, which would be important as the rainy season onset is starting later and shortening due to global climate change. The manuscript is clear and provides sufficiently detailed information on the data, methods, and results.

 Specific comments:

Please elaborate on how you determine the green-up date combining multiple methods. It seems you try to assemble those methods which produce same or similar results. I thought this could be done independently from field data, by determining the methods for assembly for each pixel. Therefore, various combinations should ensure for accounting for the diverse field conditions. But I noticed in your result, that you used a single combination of these methods which is verified by field data. Please make it clear in your method description, and how this single combination would effectively capture green-up dates in different areas

Details on the field data should be provided (maybe in a table). So far it seems the field data are only from irrigated fields. Will this affect your result?

Line 111: Title of figure 2 is not correct.

Author Response

Please see the attachment.

Author Response File: Author Response.docx