Effects of Different Rotation Combinations of Cabbage, Kidney Bean and Maize on Soil Fungal Communities and Soil Nutrients

Round 1

Reviewer 1 Report

Dear authors,

This paper must supported with in-deep and expanded discussion on the effect of different rotation combinations (different sequences of different crops) on soil nutrients and soil fungal communities and the relationships between soil nutrients and fungal communities (on the what, why and how).

Introduction only consists of two very long but unstructured paragraphs. Each paragraph should brings one main idea in the topic sentence, with several contributing sentences, linked in smooth flow and logical, and there has to be a linking word or words or sentence. Introduction section has to be concluded with the objective of the study.

Sentences bearing a scientific idea or fact have to be followed by its references or sources using [number].

Please also fix the comparison errors in the comparison of soil nutrients.

The RDA results are not clear where are the positions of the cropping sequences and the fungal genera; they should be scattered around the four axes depending on their correlation; so re-analysis may need to be done to fix the results in Fig. 5 (please check for example Front. Microb. doi: 10.3389/fmicb.2022.868312 for reference on RDA).

The discussion must be focused more on the impact of different crop sequenses, and focus the discussion on the findings of this study, which was measured and analyzed, and on the impacts of crop sequences on soil fungi and nutrients. Different species of crops not just consumes soil resources differently but also release different types of root exudates, which determine types of soil biota in the soil. Cabbage for example is not a host for mycorrhizal fungi (Glomeromycota), etc.

Comments for author File: Comments.pdf

The Introduction needs to be re-written with good structured paragraphs having logical flow between paragraphs. It also needs to be more accurate in the in-text citation.

Author Response

Response to Reviewer 1 Comments

Point 1: Dear authors,This paper must supported with in-deep and expanded discussion on the effect of different rotation combinations (different sequences of different crops) on soil nutrients and soil fungal communities and the relationships between soil nutrients and fungal communities (on the what, why and how).Introduction only consists of two very long but unstructured paragraphs. Each paragraph should brings one main idea in the topic sentence, with several contributing sentences, linked in smooth flow and logical, and there has to be a linking word or words or sentence. Introduction section has to be concluded with the objective of the studSentences bearing a scientific idea or fact have to be followed by its references or sources using [number]. Please also fix the comparison errors in the comparison of soil nutrients. The RDA results are not clear where are the positions of the cropping sequences and the fungal genera; they should be scattered around the four axes depending on their correlation; so re-analysis may need to be done to fix the results in Fig. 5 (please check for example Front. Microb. doi: 10.3389/fmicb.2022.868312 for reference on RDA). The discussion must be focused more on the impact of different crop sequenses, and focus the discussion on the findings of this study, which was measured and analyzed, and on the impacts of crop sequences on soil fungi and nutrients. Different species of crops not just consumes soil resources differently but also release different types of root exudates, which determine types of soil biota in the soil. Cabbage for example is not a host for mycorrhizal fungi (Glomeromycota), etc.

Response 1: Thank you very much for your reply and suggestions, the article has been revised according to the comments you provided.

Point 2: This paper must supported with in-deep and expanded discussion on the effect of different rotation combinations (different sequences of different crops) on soil nutrients and soil fungal communities and the relationships between soil nutrients and fungal communities (on the what, why and how).

Response 2: Thanks for your advice. We had revised it.

Point 3: Has to be defined in first mention.

Response 3: Thanks for your careful review. The definition of OTUs has been supplemented. The OTUs represent Operational Taxonomic Unit numbers.

Point 4: Introduction only consists of two very long but unstructured paragraphs. Each paragraph should brings one main idea in the topic sentence, with several contributing sentences, linked in smooth flow and logical, and there has to be a linking word or words or sentence. Introduction section has to be concluded with the objective of the study. Sentences bearing a scientific idea or fact have to be followed by its references or sources using [number].

Response 4: Thanks for your careful review. We have supplemented and trimmed the introduction section by adding some references and data on references and deleting words with repetitive meaning and little relevance to the topic.

Point 5: There must be a ref for this.

Response 5: Thanks for your advice. We have added a reference to that sentence "Chinese kidney bean output ranks first in the world".

Point 6: The effect of what?

Response 6: Thanks for your careful review. Continuous cropping has a great effect on the yield of kidney bean, which would cause large area wilting and death of phaseolus vulgaris, resulting in serious yield reduction.

Point 7: There must be a ref or supporting data for this.

Response 7: Thanks for your advice. Reference to the sentence has been added.

Point 8: Why three is crucial, why not two, or four?

Response 8: Thanks for your careful review. We chose cabbage, kidney bean and maize as test materials because these three crops are local staple crops with good economic benefits.

Point 9: The sentence from line 81 to line 85 is too long but it is not a complete sentence, and content is not clear on what the authors are trying to say.

Response 9: Thanks for your careful review. L81-L85 is a description of the purpose of the study for this trial, and we have modified the sentence.

Point 10: What was cultivated each those crops; or, was it fallow?

Response 10: Thanks for your careful review. Adopting a rotation fallow cultivation method, only one crop is planted annually, and seasonal rotation fallow cultivation is carried out in spring and winter.

Point 11: So, were they from 30 plots, or only 5 points from the whole area?

Response 11: Thanks for your careful review. There were 30 plots, and 5 points in each plot were selected for sampling, and this method was used in each plot, resulting in a total of 30 soil samples.

Point 12: Please fix the comparison between treatments in this part. What are the main focuses of the comparisons?

Response12: Thanks for your advice. We have corrected for errors in soil nutrient comparisons. This section includes comparisons between the 10 treatments, and between the same treatments for the previous crop grown, and is mainly used to illustrate the changes in soil fast-acting nutrients after the 3-year trial and the effect of crop type grown in year 3 on soil fast-acting nutrients.

Point 13: BMB was the highest while BMC was the lowest, and they ar significantly different???

Response 13: The sentence is somewhat unclear and the wording has been revised. The premise of the sentence is "Seven treatments for planting cabbage and maize in the third year of the experiment were compared "

Point 14: Where was this value from? 9.33%???

Response 14: Thanks for your careful review. AN-CMB 111.42mg/kg, AN-BBB 120.75mg/kg. The AN content of CMB decreases by 7.73% compared to BBB. 7.73%=(120.75-111.42)/120.75×100%.

Point 15: AN was also significantly different between BMB and BMC???

Response 15: Thanks for your careful review. There is a prerequisite "When the previous crop was maize", which means that only four treatments, CCM, CBM, BBM and BCM, were involved in the comparison.

Point 16: Between treatments?

Response 16: Thanks for your careful review. There is a prerequisite "When the previous crop was maize", which means that only four treatments, CCM, CBM, BBM and BCM, were involved in the comparison.

Point 17: BMB was the highest, followed by CCM, please fix this.

Response 17: Thanks for your advice. We apologize for the typographical error in this section, which has been corrected.

Point 18: This can not be generalized like this because on AP, CBM is the best.

Response 18: Thanks for your advice. We have removed the generalized sentence.

Point 19: Please fix this; what are different between what and what?

Response 19: Thanks for your careful review. This sentence compares the CCC treatment with the remaining 9 treatments, and the wording has been modified.

Point 20: This RDA is not clear where are the positions of the cropping sequences and the fungal genera; they should be scattered around the four axes depending on their correlation (please check for example Front. Microb. doi: 10.3389/fmicb.2022.868312 for reference on RDA).

Response 20: Thanks for your careful review. We are apologized that there was an error in Figure 5 during the submission process and we will resubmit Figure 5.

Point 21: Yes, but discuss what are the drivers of species diversity found in this study. So, please relate those diversity with the crop sequences.

Response 21: Thanks for your careful review. We have added a concatenation clause.

Point 22: Please discuss how these happen in relation to the findings of this study. Different species of crops not just consumes soil resources differently but also release different types of root exudates, which determine types of soil biota in the soil. Cabbage for example is not a host for mycorrhizal fungi (Glomeromycota), etc.

Response 22: Thanks for your careful review. We had revised it.

Point 23: These should be discussed why and how they happen.

Response 23: Thanks for your advice. We have explained the selection of treatments with the same preceding crops for comparison. The higher similarity of the root secretions produced when the preceding crops were grown identically resulted in less variability of soil microorganisms between treatments with the same preceding crops.

Point 24: By crops of by microbes?

Response 24: By microbes. We had revised it.

Point 25: Please refer to which results of this study, and discuss how those factors could change fungal community.

Response 25: Thanks for your advice. We had revised it. Factors such as planting crops, planting patterns, rotation years and other factors can regulate the soil rhizosphere microecosystem by changing the ratio of bacteria to fungi, and the ratio of beneficial bacteria to harmful bacteria, which can change the composition of soil fungal communities to varying degrees.

Point 26: But changes in soil pH due to different crop sequences were not measured???

Response 26: Thanks for your careful review. After re-analysis of the literature, it was found that there was no clear positive correlation between soil pH and Ascomycota, and we have truncated the pH-related content.

Point 27: Discussion has to be focused to discuss the finding of this study, not ti cite something which was not measured, such as pH changes, pathogen accumulations, etc.

Response 27: Thanks for your advice. We removed what was not relevant to the findings of the study and focused on discussing the findings of this study.

Point 28: The diversity and population of soil biota highly depend on available nutrients and types of crops and their sequences, and type of crop sequences also determine the levels and types of available nutrients and their composition in the soil. Therefore, discussion must be more focused on the interconnection of these three parties.

Response 28: Thanks for your advice. We have reviewed some relevant information, but most of the literature simply states the data or speculates based on the changes in the data, and no clear explanation for the combined changes in the 3 aspects of fast-acting nutrients, crop type, and soil fungi has been found.

Point 29: In a discussion, the author must focus discussing on how and why they happened, not just repeating the results of data analyses.

Response 29: Thanks for your careful review. We had revised it.

Reviewer 2 Report

I read with interest the manuscript “Effects of different rotation combinations of cabbage, kidney bean and maize on soil fungal communities and soil nutrients”. The article is well written and easy to read. I was amazed, however, because growing the same crop for years on the same soil is obviously destructive to the soil itself. Microbial diversity is increasingly reduced and selected and, consequently, organic matter is decreasing more and more. The consequence is that the soil no longer retains fertilizers and water and becomes increasingly impoverished until it becomes a desert. To maintain fertile soil it is necessary to rotate at least four different crops and it would also be necessary to fertilize with organic matter.

In this situation, is it not it possible to introduce two crops one after the other in the same year? For example, in September, after harvesting, could a winter cereal or a legume cover crop be sown for use as green manure before sowing next year?

From the results obtained with three rotations, and above all after a monoculture maintained for so long, the biodiversity of the soil must have been considerably impoverished and no great differences were noticed between the different treatments over the three years. I don't think a three-year rotation is enough. To restore good fertility and good microbial diversity, ten years of rotations that are as biodiversified as possible and additions of organic fertilizers and green manure are also needed.

In the description of experimental design, you say that plants are grown without irrigation; was it possible because the summer period is the rainiest?

Line 67: Phaseolus vulgaris in italics.

Line 121. From what you write, you probably sequenced part of 18S. Have you used one of the ITS primers? Describe precisely the procedures you followed, DNA isolation, PCR, etc.

Line 128. You use the abbreviations AN, AP and AK, I assume they are "available NPK". Next, however, you provide data on the total amount. Please uniform.

Line 246 e 247. You write the "relative abundance content". "Content" is not necessary, just "relative abundance"

Line 370. Cyperus esc. in italics.

Format the table 6.

In the caption of table 7 what does "features order" mean?

Figure 5. Do arrows refer to phyla? If yes, please include the names as well. But then you say that “different colors correspond to different treatments”: I see neither different colors, nor what they refer to.

Author Response

Response to Reviewer 2 Comments

Point 1: I read with interest the manuscript “Effects of different rotation combinations of cabbage, kidney bean and maize on soil fungal communities and soil nutrients”. The article is well written and easy to read. I was amazed, however, because growing the same crop for years on the same soil is obviously destructive to the soil itself. Microbial diversity is increasingly reduced and selected and, consequently, organic matter is decreasing more and more. The consequence is that the soil no longer retains fertilizers and water and becomes increasingly impoverished until it becomes a desert. To maintain fertile soil it is necessary to rotate at least four different crops and it would also be necessary to fertilize with organic matter.

In this situation, is it not it possible to introduce two crops one after the other in the same year? For example, in September, after harvesting, could a winter cereal or a legume cover crop be sown for use as green manure before sowing next year?

From the results obtained with three rotations, and above all after a monoculture maintained for so long, the biodiversity of the soil must have been considerably impoverished and no great differences were noticed between the different treatments over the three years. I don't think a three-year rotation is enough. To restore good fertility and good microbial diversity, ten years of rotations that are as biodiversified as possible and additions of organic fertilizers and green manure are also needed.

In the description of experimental design, you say that plants are grown without irrigation; was it possible because the summer period is the rainiest?

Response 1: Thanks for your advice. The experimental design in this article aims to solve the practical problems in dry farming, which is a kind of rain-fed agriculture that relies mainly on natural precipitation to engage in agricultural production in semi-arid and semi-humid arid areas without irrigation conditions.

The specific conditions of this experiment: 1. Humanities: In the rural areas of northern China, there is no enterprise development, people work outside all year round to maintain their livelihoods, and only stop working and go home to work during the annual spring sowing and autumn harvest, and let the crops grow in between without human interference. 2. Geography: The test site is He Village, Yangqu County, Taiyuan City, located in the semi-arid region of the Loess Plateau in China, which is lack of water resources and no irrigation conditions, and mainly relies on natural The area is lack of water resources, no irrigation, and mainly relies on natural precipitation, most of which falls in summer, with little rainfall in the other three seasons.

Therefore, you propose to "introduce two crops one after the other in the same year", and it is difficult for crops to grow and develop when they are sown in winter without natural precipitation and irrigation. To ensure normal crop growth, artificial irrigation is required, which is not only against the premise of dry farming, but also against the human geography of the area.

Before starting the experiment, we investigated the specific conditions of the test site, and based on the degree of pest and disease occurrence in the area and the soil conditions, a three-year crop rotation would be reasonable. A 10-year crop rotation with the addition of organic fertilizer and green manure would make the trial results clearer and more convincing.

Your views are very constructive, my sister is doing the application of organic fertilizer and straw instead of chemical fertilizer on corn, after that I will design a new experiment combining my sister's and my research direction with the advice you provided and follow up continuously.

Point 2: Line 67: Phaseolus vulgaris in italics.

Response 2: Thanks for your careful review. We had revised it.

Point 3: Line 121. From what you write, you probably sequenced part of 18S. Have you used one of the ITS primers? Describe precisely the procedures you followed, DNA isolation, PCR, etc.

Response 3: Thanks for your careful review. We had revised it.

Point 4: Line 128. You use the abbreviations AN, AP and AK, I assume they are "available NPK". Next, however, you provide data on the total amount. Please uniform.

Response 4: Thanks for your careful review. AN, AP and AK refer to the NPK in the soil that can be directly absorbed and used by the crop roots, which you consider as "available NPK". The measurement of total N, P and K can help us to understand the total NPK in the soil, but it does not directly reflect the changes in plant nutrient requirements. Therefore, when making nutrient transport measurements, soil fast-acting nutrients more accurately reflect changes brought about by crop rotation, and in most articles, people prefer to use the changes in available NPK to illustrate the problem. If you think this article needs data for all N, all P, and all K, we will make up the measurements, so please give us some time.

Point 5: Line 246 - 247. You write the "relative abundance content". "Content" is not necessary, just "relative abundance".

Response 5: Thanks for your careful review. We had revised it.

Point 6: Line 370. Cyperus esc. in italics.

Response 6: Thanks for your careful review. We had revised it.

Point 7: Format the table 6.

Response 7: Thanks for your careful review. We had revised it.

Point 8: In the caption of table 7 what does "features order" mean?

Response 8: Thanks for your careful review. The "features order" refers to the unique order of the biological class. The unique order that exists in the comparison between treatments.

Point 9: Figure 5. Do arrows refer to phyla? If yes, please include the names as well. But then you say that “different colors correspond to different treatments”: I see neither different colors, nor what they refer to.

Response 9: Thanks for your careful review. We had revised it. An error occurred during the submission of Figure 5 and we will resubmit Figure 5.