Investigation on the feasibility of straw incorporation to improve soil fertility without obviously increasing global warming potential

Zhang, Mengxue; Liao, Rujia; Zhang, Wenzhao; Fang, Cheng; Guerrero-Cruz, Simon; Táncsics, András; Zhu, Baoli; Wei, Wenxue; Sheng, Rong

doi:10.5194/egusphere-2025-6534

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https://doi.org/10.5194/egusphere-2025-6534

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02 Feb 2026

| 02 Feb 2026

Status: this preprint is open for discussion and under review for SOIL (SOIL).

Investigation on the feasibility of straw incorporation to improve soil fertility without obviously increasing global warming potential

Mengxue Zhang, Rujia Liao, Wenzhao Zhang, Cheng Fang, Simon Guerrero-Cruz, András Táncsics, Baoli Zhu, Wenxue Wei, and Rong Sheng

Abstract. The utility of rice straw as an organic fertilizer has been widely recognized as a promising approach to enhancing soil fertility. However, straw return is currently in a dilemma, as it may also provoke greenhouse gas (GHG) emissions, leading to serious environmental consequences. It is urgent to reveal the feasibility of straw incorporation regarding soil fertility improvement without notable increases in GHG emissions. Here, a soil microcosm experiment was employed to investigate the relationships between soil fertility and GHG fluxes and the underlying mechanisms influenced by straw amendments. Paddy soils were collected from a long-term rice straw incorporation field experiment. The dynamics of GHG fluxes and concentrations in soils, and the variations in the abundances of soil microbial communities were systematically determined. The results indicated that continuous rice straw incorporation at half of the harvest (ST1) obviously improved soil fertility but did not induce significant elevation of global warming potential (GWP). The minimal increase in GWP was mainly attributed to the significant reduction in N₂O emission and the slight rise in CH₄ emission compared to straw removal. The main mechanisms for these consequences were that ST1 possessed the highest nosZII abundance and the lowest nirS/nosZII ratio; meanwhile, its CH₄ production ability fluctuated around the soil CH₄ holding capacity, and most of the produced CH₄ was consumed by methanotrophs. In conclusion, rice straw can be incorporated into paddy soils at a suitable application rate, which can effectively enhance soil fertility without inducing an additional warming effect.

Received: 30 Dec 2025 – Discussion started: 02 Feb 2026

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Mengxue Zhang, Rujia Liao, Wenzhao Zhang, Cheng Fang, Simon Guerrero-Cruz, András Táncsics, Baoli Zhu, Wenxue Wei, and Rong Sheng

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CC1:
'Comment on egusphere-2025-6534', Jun Shan, 05 Feb 2026 reply
In this study, the authors claimed that rice straw could be incorporated into paddy soils by optimizing the straw rate and explained why the optimal rate minimized global warming potential mainly from the functional microbial perspective. The topic is interesting and well within the scope of SOIL journal. The MS is generally well-organized and well-written, and the methodology is sound. However, I have several comments to improve the quality of the MS. I recommend major revision before acceptance.

General comments
The first concern is about the title. The title is overstated. Investigating feasibility can include several aspects such as agronomic measures, soil types, climate regions, and land use, while the authors only focus on the rice straw rate and one paddy soil. I recommend reconsidering the title.

The authors used paddy soils from a long-term field to investigate GHG emission and microbial abundances. I acknowledge that the incubation approach has distinct advantages especially in elucidating the mechanism. The authors should claim more about why they chose to further conduct the microcosm experiment by following the field setting instead of directly sampling from the field.

The authors should explain more about why they only focused on nirS and nosZII while excluding their paired genes nirK and nosZI. I suggest adding one or two sentences in the Method section to clarify this.

The authors revealed that the soil has a holding capacity for CH₄ while not mentioning this for N₂O. From the concentration data, it seems soil did not hold N₂O at least not as long as CH₄. Why? It would be interesting if authors could explain a bit about this since the soil holds CH₄ while not holding N₂O may have implications for GHG mitigation strategy.

Besides CH₄ and N₂O, CO₂ is also an important GHG as it contributed up to 45% to the GWP (Table 2). I recommend elaborating more on the mechanisms related to CO₂ in the Discussion part.

Please improve your English and check the grammar throughout the paper.

Specific comments
Line 55-56. “This study aimed to…, and the related mechanisms”. I suggest rephrasing this sentence.
Line 66. Please add the description about water management of the field experiment since water regime could have a legacy impact on GHG emissions. This information would be valuable for potential readers interested in relevant topics.
Line 77-83. You sampled the headspace gas in the chamber and then the soil gas in the silicone tube (see Line 96-100). For consistency, I suggest adjusting the order here: For gas flux sampling, … For soil gas sampling, …
Line 84-85. “and each pot contained 1.27 kg (dry weight) of soil to reach about 10 cm in depth”. I suggest revising this sentence.
Line 99. What does “at the same time” mean? Did you sample headspace gas and soil gas simultaneously?
Line 193-195. The sentence is too long. Please revise it.
Line 249. “similar” should be “similarly”.
Line 266. It is inappropriate to use “fail to” here. We don’t expect an increase.
Line 291. I suggest deleting “with less than 5 g·m^-2”. It is meaningless to point out the number here. The GHG cumulative emissions from microcosms are incomparable among studies.
Line 293. Change “such a low” to “a much lower”, as the CH₄ cumulative emission should be only compared to the three other treatments in THIS study.
Line 298-300. Grammatical errors. Please revise the whole sentence.
Line 312-314. For now, the outlook could be more comprehensive. Consider revising this if possible.

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Citation: https://doi.org/10.5194/egusphere-2025-6534-CC1
CC2:
'Comment on egusphere-2025-6534', Jupei Shen, 06 Feb 2026 reply
Rice straw incorporation is an important measure in the current sustainable development of agriculture, but its impact on greenhouse gas emissions remains controversial. The manuscript aimed to investigate the feasibility of straw incorporation to improve soil fertility without elevating global warming potential based on a microcosm experiment. This experiment has important practical value for optimizing fertilization strategies. Generally, it is an interesting topic, and the experimental design is rigorous. However, I have some concerns that should be addressed before the consideration for publication.
In the abstract, add the treatment information. Key data is also necessary in this part.

I would recommend to further point out the shortcomings of existing studies in terms of "synergistic effects of straw incorporation on both soil fertility and greenhouse gas emission, and the underlying mechanisms" in the Introduction section, which may help highlight the importance of the research.

Provide a hypothesis for this study.

L69, “from each treatment”

L85-87, the description of treatments is not clear. The straw treatments use the same amount of straw as did in the field experiment in the corresponding soils?

L89, give more detail process for urea and straw application.

Some detailed descriptions (such as gas collection devices) can be appropriately streamlined or moved to supplementary materials. Provide a schematic diagram of the cultivation device along with actual photos can give readers a better understanding.

In the "DNA Extraction and qPCR" section, briefly explain the reasons for choosing these functional genes (such as nosZII type instead of nosZI type).

It is recommended to provide the abundance data of nirK and nosZI and also the correlation analysis between greenhouse gas fluxes and microbial gene abundance.

In table 1, it would be better add the information for soils, which is derived from field samples.

L226-227, “copies per g dry soil…”

Some statements in the discussion can be further simplified to avoid the repetition of the results, and recommend focusing more on the explanation of the mechanism and literature comparison.

If possible, supplement the discussion on the relationship between CO₂ emissions and soil carbon accumulation, such as: "Although the CO₂ emissions of ST1 treatment increased significantly, the soil organic carbon content also rose simultaneously, indicating that straw returning to the field promoted the turnover and stability of soil carbon."

More relevant studies can be cited to enhance the persuasiveness in explaining N₂O emissions.

In the discussion part, add some comments for the abundance of detected genes compared to literature.

It is also recommended to add the limitations of this research.

The manuscript would benefit from further linguistic refinement.

Reply
Citation: https://doi.org/10.5194/egusphere-2025-6534-CC2
RC1: 'Comment on egusphere-2025-6534', Anonymous Referee #1, 15 Apr 2026 reply

This study used a soil microcosm experiment to investigate the effects of straw incorporation on the relationship between soil fertility and greenhouse gas (GHG) fluxes, as well as the underlying microbial mechanisms. These are relevant and timely topics in the context of straw return and GHG mitigation. However, several issues need to be addressed before the manuscript can be considered for publication.

Introduction
1, The introduction mainly lists the effects of straw incorporation on CO2, CH4, and N2O emissions, but lacks a sufficient synthesis of the underlying regulatory mechanisms, particularly the microbially mediated processes involved in greenhouse gas production and consumption. As a result, the knowledge gap identified in the current version remains rather broad.
2, Although the study objective is stated at the end of the introduction, it has not been further distilled into clear scientific questions, and corresponding hypotheses are also lacking. The authors are therefore encouraged to explicitly state the scientific questions addressed in this study and to propose relevant hypotheses at the end of the introduction.
3, This study further conducted an indoor incubation experiment based on a 5-year field trial; however, the necessity of this design and its advantages over field observations have not been sufficiently explained in the introduction. The authors are advised to clarify the logical connection between the long-term field background and the subsequent indoor mechanistic investigation.

Materials and Methods
1, It is suggested that Section 2.1 be divided into two subsections: 2.1 Site description and experimental design and 2.2 Soil and straw sampling and preparation.
2, Line 64: Please clarify the physical condition of the straw (e.g., whether it was chopped or crushed, and its length range) and the depth at which it was incorporated. In addition, please explain why the rice straw was sieved through a 1 mm mesh during the incubation experiment (Line 73), and why the straw was fully mixed with the 0-15 cm soil layer (Line 89) instead of following the actual field situation.
3, Line 71: Please specify the temperature conditions used during the pre-incubation period.
4, Line 77: It would be helpful to add a photo of the experimental setup in the Supplementary Materials. Together with the schematic diagram, this would make the experimental procedure clearer.
5, Line 84: Why was 1.27 kg of soil used? Please clarify whether this amount was determined according to the actual field bulk density.
6, Line 96: Was the sampling conducted at a fixed time each day, for example, 9:00–10:00 a.m.? Please specify the sampling time and briefly explain the reason for this setting.
7, Line 99: Please clarify the purpose of taking 1 mL of gas from the silicone tube buried at the bottom, including what parameter it was used to measure or what role it played in the experimental design.

Results
1, According to the study objectives, soil fertility is one of the core concerns. However, the related results are currently mainly included under 3.1 Soil properties, where they are not sufficiently highlighted. The authors are suggested to strengthen the presentation of soil fertility-related results and consider reflecting this aspect more clearly in the subsection title.
2, No correlation analysis was conducted, yet terms such as “positively related to” and “negatively related to” are used in the Results section. Such wording is not rigorous without statistical support. The authors are advised to either perform correlation analysis or revise these statements to more descriptive expressions.
3, The incubation experiment included both flooding and drainage periods, and Fig. 1 shows that both CO2 and CH4 emissions peaked in each stage. However, the Results section does not describe these two periods separately. Since the experimental design clearly distinguished them, the authors are encouraged to further compare the emission patterns between the flooding and drainage periods. In addition, it is suggested that cumulative emissions in Table 2 be calculated separately for the two stages to better reflect their differences.

Discussion
1, The expression “We hypothesized that …” in Line 264 is not appropriate in the Discussion section. Research hypotheses should normally be presented in the Introduction rather than introduced for the first time in the Discussion. The authors are advised to move the hypothesis to the end of the Introduction and then discuss whether it is supported by the results.
2, The discussion of soil fertility is still insufficient. At present, the effect of ST1 on soil fertility is only briefly mentioned in one sentence (Line 266), which does not fully respond to the study objectives. The authors are encouraged to specify which soil fertility-related indicators were improved by ST1 and to further analyze the possible reasons based on the results.
3, The reason why ST1 did not significantly increase GWP is not clearly discussed. According to Table 2, although ST1 significantly increased the cumulative emissions of CO2 and CH4, it also significantly reduced N2O emissions, which likely explains why GWP did not increase markedly. This point should be stated more explicitly in the Discussion, together with the relative contributions of different gases to GWP. At present, the manuscript only discusses the reason for the increase in N2O under CK, while the overall effect of ST1 is not sufficiently addressed.
4, If the authors intend to emphasize the regulatory role of microbial changes in GHG or GWP, corresponding correlation analyses are recommended.
5, Line 293: There is a grammatical problem in this sentence. “Such as” should not be followed by a complete sentence, and the sentence structure should be revised.
6, Line 294: The phrase “The question is why …” is rather colloquial and adds little information. It is suggested to delete this expression.

Reply

Citation: https://doi.org/10.5194/egusphere-2025-6534-RC1

Mengxue Zhang, Rujia Liao, Wenzhao Zhang, Cheng Fang, Simon Guerrero-Cruz, András Táncsics, Baoli Zhu, Wenxue Wei, and Rong Sheng

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https://doi.org/10.5194/egusphere-2025-6534-supplement

Mengxue Zhang, Rujia Liao, Wenzhao Zhang, Cheng Fang, Simon Guerrero-Cruz, András Táncsics, Baoli Zhu, Wenxue Wei, and Rong Sheng

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Short summary

To return straw or not to return? We demonstrate that rice straw incorporation at half of the harvest enhanced soil fertility without additional global warming potential (GWP). This minimal increase in GWP relied on the highest nosZII abundance and the lowest nirS/nosZII ratio, and the CH₄ production being just above the soil CH₄ holding capacity. We offer a viable strategy to scientifically manage rice straw for climate-smart sustainable rice agriculture.


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