Adaptation to Climate Change Effects by Cultivar and Sowing Date Selection for Maize in the Northeast China Plain

Round 1

Reviewer 1 Report

General

This paper used a combination of field experiments and model simulations to explore how cultivar selection and sowing date effected maize yields under changing climate conditions in the Northeast China Plain. I appreciated the focus on solutions to climate change effects, rather than just the negative impacts and the use of management practices that could be realistically modified in the short term.

Change “Climate Warming” to “Climate Change”. Warming implies that you are only looking at increased temperatures, but changes in rainfall and cloud cover are also important. I would suggest making this change throughout the paper.

 

Specific

Lines 2-3: Change the title to “Mitigating Climate Change Effects by Cultivar and Sowing Date Selection for Maize in the Northeast China Plain”.

Line 12: Add “the” before Northeast China Plain.

Line 13: Change “China” to “Chinese”.

Lines 16-20: Break this up into more sentences. For example: “Delayed sowing led to less cloudy and rainy weather during flowering and reduced the negative effect on kernel number. High diurnal temperature differences and less rainfall during the grain-filling stage also increased the 1000-kernel weight. Delayed sowing, however, also significantly increased the risk of early senescence and frost (>80%) in middle and high latitude areas.”

 

Lines 21: “Under early sowing (I, conventional sowing date)” Early sowing implies sowing before the conventional sowing date. If conventional sowing date is a range of dates, please make this clearer.

 

Lines 21-24: Consider changing the sentence as follows: “The grain yield of a long-season cultivar (LS) was significantly higher under early sowing (I) (6.2%–19.9%), than under medium sowing (II) or late sowing (III) in middle and high latitude areas of the NEC, and higher than that of an early sown (I) short-season (SS) or medium-season cultivar (MS).”

 

Lines 26-29: Consider changing to “Therefore, under climate change, LS sown early in high and medium latitudes and MS sown medium in low latitude were the appropriate cultivar and sowing date choices, which could mitigate the stress of high temperatures and reduce the risk of early senescence and frost.”

 

Lines 36-39: Consider changing to: “Climate change is one of the major challenges of the 21st century. A rapid, 3 ℃ increase in the global average surface temperature is expected by the end of this century, due to huge emissions of greenhouse gases since the 1970s [1], extensively affecting the agricultural sector [2–4].”

 

Lines 39-40: Consider changing to: “Higher temperatures may benefit some crops, but are disadvantageous to maize production [5].”

 

Line 48: Change to “Since the 1960s” and change “maize yield” to “maize yields”.

 

Lines 53-54: Consider changing to “However, inadequate temperature accumulation from April to October is one of the main reasons for spring maize production decreasing in the NEC [9,10].”

 

Lines 60-64: Consider changing to: “However, climate change will not be advantageous to the development of maize production in low latitude areas. High temperatures, and especially extreme temperatures, before and during the flowering period, can seriously affect pollen germination and pollination, and can lead to the grain filling time shortening and the yield declining [12].”

 

Lines 64-69: Consider changing to: “Also, other studies showed that while higher average temperatures during sowing and maturity are beneficial for maize yields, excessive rainfall or prolonged cloudy and rainy weather, especially during sowing and flowering, is harmful [10,13]. Therefore, the interaction of rising temperatures, cloudy, rainy weather during flowering, and the amount of temperature accumulation needed by various maize cultivars in the NEC needs to be urgently addressed.”

 

Line 72: Change “cultivar” to “cultivars”.

 

Lines 73-75: Consider changing to: “Maize production depends heavily on local climate conditions, as temperature, rainfall and solar radiation are important factors affecting maize yield [15].”

 

Line 80: Change “cultivar” to “cultivars”.

 

Lines 86-90: Consider changing to: “The objectives were (1) to evaluate the effects of climate factors on the kernel number, thousand kernels weight and grain yield, and analyze the risks of high temperature, low radiation interception due to cloudy weather, and harvest losses caused by early senescence and frost; (2) to evaluate the effects of cultivar and sowing date selection on grain yield for the NEC using the APSIM model.”

 

Lines 92-97: Could you please add a brief description of the soils at the various sites?

 

Lines 93: Replace “lies” with “lies in the”.

 

Lines 95-97: Please add a source for this data. Also, why are the means given as ranges? There should only be one mean annual temperature and one mean annual precipitation. It would be more helpful to have the mean temperature during the growing season and not across the whole year. Cold winter temperatures lower the mean temperature, but do not actually have any effect on maize production, as maize is not grown in the winter.

 

Lines 102-104: Consider changing to: “Cultivars and sowing dates were set for each experimental station, using the maize cultivars widely grown in the NEC. The planting density was the local conventional planting density (Table 1).” Also, you used different cultivars for different stations. Could you please be more specific why you did this? You currently only say that you picked cultivars that were popular in the entire NEC, so how did you determine the regional differences within the NEC.

 

Lines 106-108: It might be helpful to also report the fertilizer in terms of kg N, P, and K per ha.

 

Lines 110-112: Consider changing to: “The time of flowering (VT) and physiological maturity (PM) were recorded, as well as the grain yield (14% water content), kernel number, and 1000-kernel weight (14% water content) at PM.”

 

Lines 123-125: Consider changing to: “APSIM was used to simulate days from sowing to flowering, days from sowing to maturity, and the grain yield of maize at the study sites [19,20].”

 

Lines 137-138: Are you using the same three generic cultivars (SS, MS, LS) for each location, or are you using different cultivars for each location like you did for the field experiments?

 

Lines 140-142: Consider changing to: “Lastly, we considered the effect of elevated CO2 on maize yields to be negligible for this analysis, even though CO2 concentration increased from 1980 (350 pm) to 2019 (410 pm), as maize is a C4 crop [19]. “ 

 

Table 1: Please clarify what the °C d values given are. Are they GDD from planting to maturity?

 

Line 154: Please define Tbase.

 

Lines 180-182: Consider changing to: “In the central NEC, medium sowing (II) of SS resulted in higher grain yields than early sowing (I, 5.9%) and late sowing (III, 5.3%), but there was no significant difference in SS yields among sowing dates in the north and south of the NEC.”

 

Lines 182-183: Consider changing to: “The grain yield of MS II was higher than MS I and MS III for all study locations.”

 

Lines 183-185: Consider changing to: “In the northern and central NEC, the grain yield of LS I was highest (11.0 and 14.4 t ha- 1 respectively), but yields significantly decreased with delayed sowing dates (8.1%–13.6% and 5.9%–16.6% for II and III respectively).  Sowing date did not, however, significantly affect LS yields in the southern NEC.”

 

Figure 2: Those are some very nice looking simulations. In the description change “A,B,C” to “d,e,f”.

 

Figure 3: Consider changing the description to: “Grain yields of different cultivars and sowing dates in the Northeast China Plain. (a) North, Keshan station, (b) Central, Gongzhuling station, (c) South, Shenyang station. SS: short- season cultivars, MS: medium-season cultivars, LS: long-season cultivars.” Also, you might want to explain the letters (a-e) above the bars and what I, II, and III stand for.

 

Line 196: Consider replacing “in NEC”, with “for all study locations”.

 

Line 199: Replace “growth degree days” with “growing degree days”.

 

Lines 202-204: Consider changing to: “Positive correlations were observed between 1000-kernel weight and ΔT, RD and SRAD for the organic formation stage (P < 0.05). Negative correlations were observed between 1000-kernel weight and Tmax, Tmin and GDD (P < 0.05).”

 

Lines 206-209: Consider changing to: “Precipitation had a negative correlation with kernel number (P < 0.05). A positive correlation between 1000-kernel weight and precipitation was observed for the flowering stage (P < 0.05), while 1000-kernel weight was negatively correlated with RD and ΔT (P < 0.05).”

 

Line 210: Replace “, HSD and Tmin” with “, but HSD and Tmin”.

 

Lines 211-212: This sentence is unclear. What is negatively correlated with RD, 1000-kernel weight or SRAD?

 

Lines 214-215: Replaced “correlated” with “correlation”.

 

Line 216: What did Tmax and Tmin negatively influence? Please clarify.

 

Figure 4: Please provide units and explain the scales used for the graphs. Why are there negative values on the axes? Also, the trendline is missing in graph c. What is r?

 

Table 2: It unclear what is meant by relationship. Is it the slope of the linear model? Could you please also explain the * symbols.

 

Lines 228-230: This sentence is a bit confusing. Looking at the temperatures in Figure 5, heat stress (T > 32 C) was possible (though not inevitable) for much of the early to mid-season, but temperatures were consistently below 32 C for the later season (i.e. heat stress was not inevitable for the “whole growth stage of maize”).

 

Lines 230-232: This sentence is discussing the entire growth stage, but references Figure 6b, which only shows the grain fill stage. It is also unclear how the 11.9-65.7 mm of precipitation tie in with the rest of the sentence. Is the range of precipitation seen during the 10 days surrounding flowering?

 

Line 235: Replace “precipitation of grain-filling stage decreased with delaying sowing date” with “precipitation during grain-filling stage decreased with the delaying of sowing date”.

 

Figure 5: Graphs 5d-f should have the same scale for easier comparison.

 

Lines 246-247: I thought one of the issues facing maize production in the NEC was insufficient accumulated temperature. Why is increasing accumulated temperature causing yield decreases?

 

Lines 246-249: Consider changing to: “As the temperature and the effective accumulated temperature increased (Figure A1), the grain yield in the NEC decreased and the sowing date for maximum grain yield was delayed and yield fluctuation increased (Figure 7), but the frost risk decreased (Figure 8).”

 

Lines 249-250: It seems odd to report ranges for 1980-1999 and 2000-2019. Either report a range from 1980-2019 or report two mean yields.

 

Line 251: Consider changing to “SS. There was no significant difference in yield across the sowing dates for all three cultivars.”

 

Lines 254-255: Consider changing to “but the sowing date had no significant difference on the yield”.

 

Line 256: Again, reporting two different yield ranges here seems a bit cumbersome.

 

Lines 256-258: Consider changing to: “Delayed sowing caused a significant increase (up to 80%) in early senescence and frost risk.”

 

Figure 6: Consider changing the caption to: “Simulated average diurnal temperature difference (ΔT, a), precipitation (b), and solar radiation (SRAD, c) for different maize cultivars and sowing dates during grain-filling stage in the NEC.” Also, Define SS, MS, LS, I, II, and III. A figure should be able to be interpreted without having to read the rest of the paper.

 

Figure 7: Define I, II, and III and replace “Sorth” with “South”.

 

Figure 8: Define I, II, and III and replace “Sorth” with “South”.

 

Line 271: Change “temperature” to “temperatures”. Perhaps use “extreme” instead of “high”.  

 

Lines 272-273: Consider changing to: “…development. Persistent extreme-temperature conditions will decrease the setting rate, or even cause extinction if lasting for several days [24–26].”

 

Lines 279-281: Is this range of heat stress risk for all cultivars and planting dates? Make it clearer that this is based on previous findings.

 

Line 300: Change “radiations” to “radiation”.

 

Lines 314-318: Consider changing to: “At the mid and high latitudes, high temperatures will increase GDD, making the area suitable for longer season cultivars (Figure 7), which will increase the grain fill period and benefit yield formation [36].”

 

Lines 321-322: Change to “…reducing photosynthetic rate and water availability…”.

 

Line 322: Replace “decreased” with “decrease”.

 

Discussion Section: While it might be outside of the scope of this study, it would be good to mention that future studies should run similar modeling experiments using simulated future climate data for multiple RCPs.

 

Line 336: Replace “delaying sowed” with “delayed sowing”.

 

Lines 336-340: Consider changing to: “Under climate change conditions, long-season cultivars sown early in high and medium latitudes and medium-season cultivars sown medium in low latitudes were the appropriate cultivar and sowing date choices, which could mitigate the stress of high temperatures, and reduce the risk of premature harvest caused by early senescence and frost.”

 

 

 

 

 

 

 

Author Response

Dear reviewer, 

Thank you for your positive comments and valuable suggestions to improve the quality of our manuscript. The comments are laid out the attachment in black font and specific concerns have been numbered. Our responses are given in red font and changes/additions to the manuscript are marked up using the “Track Changes” function. 

Please see the attachment.

Kind regards, 

Yongjun Wang, Xaingfei Han

April 5, 2022

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors analyze corn production in the Northeast China Plain (NEC) using the APSIM model calibrated with observational data taken at three experimental sites in the area. The main deduction is that a careful choice of the Cv and the sowing date are excellent tools to alleviate the climate warming on maize production and that these tools should be coupled with the choice of cultivars (e.g., heat-tolerant cultivars) and management options (e.g., fertilization, irrigation) to reduce yield losses.

The argument is certainly interesting for this journal because the adaptation is important for maize growers but I think that the work is often obscure and not well prepared.

For example I don’t understand:

- why in the title is adopted the concept of "mitigation" in place of "adaptation" that in my view is the right term

- what is the ”Organic formation stage”

- why in some cases it is used the past tense of verbs speaking of arguments that are clearly referred to the future, like the evolution of temperatures

- why are used sentences beginning with “and” or “but” (I think that in a scientific paper this should be avoided).

- why authors say “a weather station at the experimental site” (row 116) when the experimental sites are three.

I could give other examples but I'll stop here.

In conclusion I think that it is mandatory that the authors check carefully the consistency of the work and revise carefully the English language before continuing with the review.

Author Response

Dear reviewer, 

We feel great thanks for your professional review work on our article.  According to your nice suggestions and the native speakers, we have made extensive corrections to our previous draft. The comments are laid out the attachment in black font and specific concerns have been numbered. Our responses are given in red font and changes/additions to the manuscript are marked up using the “Track Changes” function. 

Please see the attachment.

Your sincerely,

Yongjun Wang, Xiangfei Han

April 5, 2022

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have modified the work according to my wishes. However persist some problems that are hereafter listed.

1. the Authors agree with my objection (why in the title is adopted the concept of mitigation in place of adaptation, that in my view is the right term?) but persist in their error.

I remember that the UNEP definition of mitigation is: Climate Change Mitigation refers to efforts to reduce or prevent emission of greenhouse gases. So in my view the right title could be something like << Adaptation to Climate Change Effects by Cultivar and Sowing Date Selection for Maize in the Northeast China Plain>>

2. At row 121 the authors write that “. The Penman-Monteith formula was used to convert sunshine duration into solar radiation [19]”. I remember that Allen et al (1998) present only the reference evapotranspiration equation of Penman-Monteith. Please check the correctness of your reference.
3. At Row 211 and in other places of the work the authors use “diurnal temperature (∆T)” or “diurnal temperature difference (∆T)”. I suggest to use of “daily thermal range (∆T)”
4. At row 254: I don’t understand the meaning of “the northern NEC was 25.2 ± 5.1 mm per ten-day, of which the random and fluctuating were lower…”
5. Caption of figure 6: I don't understand why the authors state that weather data shown in this figure are simulated. Please check it.
6. Row 306: the authors write “However, with the intensification of global change, the frequency of extremely high temperatures will continue to increase”. It could be considered that we are facing forecasts that are always affected by incertitude. So in my view it could be more correct to write something like “However, with the intensification of global change, the frequency of extremely high temperatures is expected to increase”.
7. Row 330: authors stated that “high solar radiation generally lead to high temperature, and low solar radiation lead to low temperature”. This statement has no general value as for example if you increase the altitude, solar radiation rises while the temperature decreases.
8. Row 333: the phrase “the more significant reduction of solar radiation, the higher reduction of the yield” repeats the same concept stated in the previous phrase. I suggest to delete it.
9. Row 342: the authors write “As global change goes on, the impact range expands and the frequency and intensity of extreme events such as heat and drought that may be encountered are more intense”. As stated for row 306, we are facing forecasts that are always affected by incertitude. So in my view could be more correct to write something like “However, with the intensification of global change, the frequency and intensity of extreme events are expected to increase”.
10. Row 361: I don’t understand the meaning of this phrase: “these decisions are not given but are also affected by climate change”. Please check it.

 

Moreover I'd like to give to the authors the following suggestions.

Row 22: please use “under early sowing (I)” in place of “under sowing date (I)”

Row 39: please use “but are disadvantageous to maize production” in place of “but disadvantageous to maize production”

Row 48: please use “was slowed down” in place of “is slowing down”

Row 104: please use “the impact of cultivars” in place of “the impacts of differing cultivars”

Row 128: please use “phenological development of maize” in place of “phenological development of the maize”

Row 230: please use “negatively influenced it” in place of “negatively influenced”

Row 270: please use “the grain yields of 2000−2019 decreased for all study locations, the sowing date…” in place of “the grain yields of 2000−2019 was decreased for all study locations and the sowing date…”

Row 278: please use “difference in the grain yield.” in place of “difference on the grain yield.”

Row 320: in this specific case it could be more correct to use "weather” in place of “climate”

Row 322: please use “temperature and solar radiation” in place of “the temperature and solar radiation”

Rows 331 and 379: Please don’t use “And” at the beginning of the phrase.

Author Response

Dear reviewer,

We feel great thanks for your professional review work on our article. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. The comments are laid out the attachment in black font and specific concerns have been numbered. Our responses are given in red font and changes/additions to the manuscript are marked up using the “Track Changes” function.

Please see the attachment.

Your sincerely,

Yongjun Wang, Xiangfei Han

April 12, 2022

Author Response File: Author Response.pdf