Simulating the Impact of Long-Term Fertilization on Basic Soil Productivity in a Rainfed Winter Wheat System

Round 1

Reviewer 1 Report

The manuscript “Simulating the Impact of Long-term Fertilization on Basic Soil Productivity in a Rainfed Winter Wheat System" aims at assessing the BSP of winter wheat under different fertilizer application treatments. This manuscript needs significant revision in terms of English editing. Also, the discussion and methodology needs major improvement. Therefore, this manuscript cannot be recommended for publication in its current form.

L127: Daily as time step? Needs revision

L148-152: you need to be consistent in using past and present tense in one paragraph

L153-155: RMSE and d-index do evaluate the performance of the model to predict the data but they work differently. Please describe briefly how these two statistical indicator works. Also explain why nRMSE is used along with RMSE.

If you are using subscripts in the equations, use them in text as well.

Mention the range of d-index. It is 0 and 1. Don’t just say close to one.

Correct this sentence in line L154-155

‘The values of RMSE and d-index determine the ability of the model to “accurately” predict the experimental data.’

L205: last two years (not second two years). You should try to write number from one to nine in text form in manuscript. From ten onwards you can use numeric (10,11,…).

L207: You are using R² in your manuscript at several places but you never mentioned in the methodology about what it is?  

L266-274: this part should go in the introduction.

L281: which values? Yours or others? It should be ‘Inconsistent’ not ‘Inconsistence’

L287-290: Revised this sentence so that it make more sense.

L304: Is it a casual conversation? Or a scientific paper? Need to revise the first sentence.

L320: inaccuracy? What do you mean by this?

L352: Not after 26 years. The BSP was increasing over the time.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript “Simulating the impact of long-term fertilization on basic soil productivity in a rainfed winter wheat system” presents a work on the assessment of the variation of the basic soil productivity (BSP) for the winter wheat cultivation under different fertilization treatments. The manuscript is quite easy to read and understand and has a well-organized structure but some parts can benefit from a review by a native English speaker (e.g. line 304-305 “To date, how to accurately assess BSP is still differ from researchers.” Line 319-320 “Our results proved that the calculated contribution percentage of BSP was inaccuracy by using the yield of the long-term no-fertilization…”. Line 335-226 “ However, Tang et al pointed that the ability of suppling potassium of soil was the main factor to determine the contribution…”). The work uses data collected from a long-term experiment with six fertilization treatments and is based on the use of the DSSAT model.

 

GENERAL COMMENTS AND QUESTIONS

In section 2.1, the authors reported that the initial soil properties were analyzed for the 0-15 cm depth but then, in table 1, information is reported down to 100 cm depth. Can the authors explain this difference?

Again in section 2.1, the authors reported the amount of nitrogen and phosphorous provided with mineral fertilization. How much nitrogen was provided with manure? How much was the nitrogen returned to the soil with straw incorporation? How much nitrogen was applied (in total) in the SNP and MNP treatments? I am wondering if a larger amount of nitrogen was applied in the MNP treatment and this is influencing the results presented in this paper. Was the increased contribution percentage of BSP found in the SNP and MNP due to a larger amount of nutrients applied or was it because of the form in which nutrients were provided? Please discuss this point.

In section 2.2.2, how close to the experimental field was the weather station that collected the weather data used as input for the DSSAT model?

In section 2.2.3, what is the “main experiment” that the authors refer to for the soil data? This question is connected to the first one (about section 2.1). Moreover, table 1 reports two sets of soil data, one referred to 1979 and one referred to 2000. Which set of data was used in the simulation? Did the authors simulate different periods?

I would suggest adding a new section before the current section 2.3. The new section can describe how the simulation was set up (e.g. the simulation period began in 1979 covering a period of X years. Soil data from year yyyy were used to inform the DSSAT model and a management was created to cover the period from X1 to X2). In the case of the management, how the authors treated the period from 1997 to 2000? Were the two years of winter wheat, one year of sorghum, and one year of soybean included in the simulation or not? Did the authors perform a continuous simulation for the entire period?

In section 2.3, why did the authors used the data from the SNP treatment to calibrate the winter wheat genetic parameters?

In section 2.4, can the authors provide more information on how the simulation for the BSP was conducted? Giving an example, we can consider the simulated period as 2000-2010. How was the BSP of year 2000 calculated? To calculate the BSP of year 2009 (or any other year), was the DSSAT model run from 2000 to 2009 or just from the year before? I think this type of information is useful and can help the readers to understand the methodology used here (even the work cited by the authors [44] does not provide much more information).

In lines 190-193, the authors stated that because the slope of the regression line between simulated and observed values was significantly different from one, it was possible to use DSSAT to predict wheat grain yield and soil productivity. I think the authors mean that the slope of the regression line was NOT significantly different from one (or am I missing something here?). Second, the authors tested the model for crop yield but not for the simulation of soil dynamics. Would it be possible to evaluate the performance of the model in simulating processes or factors related to soil fertility? For instance, carbon or nitrogen content at the beginning and at the end of the experiment?

Lines 204-205, the authors stated that the BSP of winter wheat fluctuated in a six-year cycle and they refer to figure 2. I think this trend is not clear from the figure (I can see some drops and spikes in the BSP but I don’t see a clear pattern). Moreover, if the authors consider this trend important, can explain what is causing it?

At the beginning of section 4.1, the authors stated that the performance in simulating BSL depends on the accuracy of the calibration of crop genetics parameters. What is the authors’ opinion on the importance of how the model simulates processes such as soil organic matter mineralization, nitrogen losses, soil water content, that affect the nutrients availability and crop growth?

At the end of section 4.2, the authors reported that including organic fertilizer or straw improved the contribution of the BSP. Can the authors elaborate on this? What is the reason for this result?

 

SPECIFIC COMMENTS

Line 67, add a space between reference n. 23 and the previous word.

Line 79, add a space between reference n. 29,30 and the previous word.

Line 80, add a space between reference n. 36, 37; reference 38-40; reference 41, and the previous word.

Line 81, add a space between reference n. 42,43 and the previous word.

Line 81-82, I think something is missing in the sentence because “such as” does not fit the context of the sentence.

Line 96, I would change “occurred” with the present “occurs”.

Line 107, Because the description usually goes before the abbreviation used, and for consistency with the form used before, I would change point (v) from the current form to (v) manure input annually (M).

Line 110, was the straw added from outside the field or was actually returned (crop residue incorporated into the soil)?

Line 112, I would remove the word “the” at the beginning of the sentence “The continuous winter wheat…”.

Line 123, check the use of the word experimental. Should it be “experiments”?

Line 142, table 1. Since the unit of each variable is below the text, I would eliminate the comma. You can put the units between parenthesis.

Line 170, this might not be important but I found a different reference for the SSP: SPSS software, IBM Corp. Released 2010. IBM SPSS Statistics for Windows, Version 19.0. Armonk, NY: IBM Corp.

Line 197, check the big black dot in the unit at the beginning of the line.

Line 200, is the dotted line the 1:1? Also, usually, the model evaluation is done placing the observed values in the y-axes and the simulated values on the x-values (Ecological modeling, 216(2008) 316-322).

Line 215, figure 2. Some abbreviations and symbols in the legend are overlapping.

Line 225, figure 3. I would suggest removing the legend and adding the name of the treatment under each bar.

Line 239, figure 4. The abbreviation SNP is overlapping with the symbol used for MNP.

Line 269, add a space between reference 28,30 and the previous word.

Line 278, add a space between reference 32 and the previous word.

Line 283, add a space between reference 41 and the previous word.

Line 285, add a space between reference 59 and the previous word.

Line 325, add a space between reference 23 and the following word,

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

N/A