the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 May 2022
Soil and crop management practices and the water regulation functions of soils: a synthesis of meta-analyses relevant to European agriculture
Abstract. Adopting soil and crop management practices that conserve or enhance soil structure is critical for supporting the sustainable adaptation of agriculture to climate change, as it should help maintain agricultural production in the face of increasing drought or water excess without impairing environmental quality. In this paper, we evaluate the evidence for this assertion by synthesizing the results of 34 published meta-analyses of the effects of such practices on soil physical and hydraulic properties relevant for climate change adaptation in European agriculture. We also review an additional 127 meta-analyses that investigated synergies and trade-offs or help to explain the effects of soil and crop management in terms of the underlying processes and mechanisms. Finally, we identify how responses to alternative soil-crop management systems vary under contrasting agro-environmental conditions across Europe. This information may help practitioners and policymakers to draw context-specific conclusions concerning the efficacy of management practices as climate adaptation tools.
Our synthesis demonstrates that organic soil amendments and the adoption of practices that maintain “continuous living cover” result in significant benefits for the water regulation function of soils, mostly arising from the additional carbon inputs to soil and the stimulation of biological processes. These effects are clearly related to improved soil aggregation and enhanced bio-porosity, both of which reduce surface runoff and increase infiltration. One potentially negative consequence of these systems is a reduction in soil water storage and groundwater recharge, which may be problematic in dry climates. Some important synergies are reductions in nitrate leaching to groundwater and greenhouse gas emissions for non-leguminous cover crop systems. The benefits of reducing tillage intensity appear much less clear-cut. Increases in soil bulk density due to traffic compaction are commonly reported. However, biological activity is enhanced under reduced tillage intensity, which should improve soil structure, infiltration capacity, and reduce surface runoff and the losses of agro-chemicals to surface water. However, the evidence for these beneficial effects is inconclusive, while significant trade-offs include yield penalties and increases in greenhouse gas emissions and the risks of leaching of pesticides and nitrate.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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RC1: 'Comment on egusphere-2022-270', Anonymous Referee #1, 10 Jun 2022
I appreciated the opportunity to review this manuscript. The authors present a well written, easy to read synthesis that outlines the knowns and knowledge gaps around a complex topic. I commend them for finding ways to simply visualize a number of concepts -- different agricultural practices related to sustainable agriculture and their impacts on various components of water regulation. I would encourage the authors to consider a few additions to clarify their methods and results.
The statement in the methods (lines 109-110) is quite brief in regards to how data was extracted from the meta-analyses. If I am following correctly it appears the authors visually from graphs or quantiatively from tables if effect sizes were significnatly above zero, below zero or were not different from zero, and then counted the n=value from these studies. It is not entirely clear to me how effect size is counted. Is this one per study (i.e. one effect size per MA?) or the total in the studies that were combined, and therefore 1 effect size = 1 field site embedded within one meta-analysis? I believe it is the latter. I encourage the authors to clarify. I also encourage the authors to consider if the lanugage "increase, decrease, no effect" is the same as "positive, neutral, negative". The latter have a connotation that is assumed by the reader, while the former are (in my opinion) more descriptive of the actual effects. For example, a decrease in runoff, while "negative" in nature, could be perceived as a positive effect of a management practice.
Although I found the manuscript generally easy to read and follow, I believe that the short intro and methods section are incongruent with the very long results & discussion. I encourage the authors to review and look for opportunities to be more concise. For example the discussion of tillage is quite lengthy, and although it is interesting to cover some elements of yield impacts, tradeoffs, etc. I am not sure that lenghty discussion as to the paper. And further, although the introduction discusses/focuses on conservation agriculture, the practices outlined in the paper are far broader in scope. I encourage the authors to consider a slight reframing of why specific practices were selected to focus on in this analysis. I do appreciate that the selection was broad, as it allows for a quick visualization/comparison of what properties and practices are more widely studies, but again think this decision needs more clarification.
I disagree with the authors final assessment in line 534 that continuous living cover reductions in SWS/recharge will outweigh increases due to carbon sequestration. While there may be concern of water limitations in drier climates, I do not believe the evidence presented supports this perception as there are few studies that look directly at this effect (judging by the gaps in evaporation and water content associated with the cropping systems practices). The benefits discussed in terms of soil physical improvements, plus benefits from carbon, with the uncertainties of rainfall variability and increases in precipitation in many places, even semiarid regions, make this assertion one that deserves more attention.
There is a small typo on line 112 - believe the first word in the sentence should be "We..."
Citation: https://doi.org/10.5194/egusphere-2022-270-RC1 -
AC1: 'Reply on RC1', Sarah Garré, 25 Jul 2022
The statement in the methods (lines 109-110) is quite brief in regards to how data was extracted from the meta-analyses. If I am following correctly it appears the authors visually from graphs or quantitatively from tables if effect sizes were significantly above zero, below zero or were not different from zero, and then counted the n=value from these studies. It is not entirely clear to me how effect size is counted. Is this one per study (i.e. one effect size per MA?) or the total in the studies that were combined, and therefore 1 effect size = 1 field site embedded within one meta-analysis? I believe it is the latter. I encourage the authors to clarify.
The number reported at line 108 is the total number of overall (average) effects sizes (i.e. the number of overall effects sizes for all combinations of management practices and target variables reported among all MA’s included in our analysis. We will clarify this.
I also encourage the authors to consider if the language "increase, decrease, no effect" is the same as "positive, neutral, negative". The latter have a connotation that is assumed by the reader, while the former are (in my opinion) more descriptive of the actual effects. For example, a decrease in runoff, while "negative" in nature, could be perceived as a positive effect of a management practice.
Yes, we did consider this aspect. The direction of the effect sizes reported in the paper are purely statistical and therefore have no connotation of value. We decided to report the effects in a statistical sense, because in some instances it’s not clear whether an effect would be beneficial or detrimental.
It was noted briefly in the caption to figure 5 (line 163) that the effects are statistical, but we will also make this clear in the text in the revised version of the paper.
We will also add the following information more clearly on how the graph was constructed:
To build Figure 5, we used a qualitative approach. From the figure reported in the meta-analyses, the overall effect size was extracted qualitatively. This means that if the average log response ratio and the entirely of 95% confidence interval was larger than 0 (so a response ratio of 1, 0 in log scale), it was considered as positive. The word "positive" here refers to the sign of the overall response ratio on a log scale. If some of the confidence interval overlapped 0, a "neutral" effect was chosen. If all confidence intervals were smaller than 0, the overall effect was considered as "negative". For all overall effects retrieved, the number of individual effect sizes used to compute the overall effect was also collected. For a given pair of practice and soil parameters, a pie chart representing the overall effects as a proportion of the number of individual effect sizes they summarised, is represented. There are situations where several meta-analyses can have information on the same pair, which can lead to pie charts with multiple colours. For instance, if a MA1 has a positive overall effect from 25 individual effect sizes and MA2 has a negative overall effect from 75 individual effect sizes, the pie chart will be one quarter orange (positive) and three quarters blue (negative). Note that that these proportions are qualitative and not quantitative. Indeed, we do not have the information on whether the individual effect size is positive, negative or neutral, but we only interpret the overall effect reported in the meta-analysis. The same figure with individual effect size would give other proportions (=quantitative approach). However, the trends between the qualitative and the quantitative approach will be similar. Several meta-analysis can also contain information about the same primary studies. This is shown in the redundancy analysis later.
Although I found the manuscript generally easy to read and follow, I believe that the short intro and methods section are incongruent with the very long results & discussion. I encourage the authors to review and look for opportunities to be more concise. For example the discussion of tillage is quite lengthy, and although it is interesting to cover some elements of yield impacts, tradeoffs, etc. I am not sure that lenghty discussion as to the paper. And further, although the introduction discusses/focuses on conservation agriculture, the practices outlined in the paper are far broader in scope. I encourage the authors to consider a slight reframing of why specific practices were selected to focus on in this analysis. I do appreciate that the selection was broad, as it allows for a quick visualization/comparison of what properties and practices are more widely studies, but again think this decision needs more clarification.
Yes, we agree. We did mention the terms climate-smart and regenerative agriculture in the introduction at lines 40-43. In the revised version, we will make it clearer that our synthesis is not exclusively focused on conservation agriculture.
I disagree with the authors final assessment in line 534 that continuous living cover reductions in SWS/recharge will outweigh increases due to carbon sequestration. While there may be concern of water limitations in drier climates, I do not believe the evidence presented supports this perception as there are few studies that look directly at this effect (judging by the gaps in evaporation and water content associated with the cropping systems practices). The benefits discussed in terms of soil physical improvements, plus benefits from carbon, with the uncertainties of rainfall variability and increases in precipitation in many places, even semiarid regions, make this assertion one that deserves more attention.
Yes, we agree. We will modify this statement to say that although there is some cause for concern, there is currently little empirical evidence that would allow us to draw any firm conclusions, and that more research is therefore needed.
There is a small typo on line 112 - believe the first word in the sentence should be "We..."
Thanks. We will correct this
Citation: https://doi.org/10.5194/egusphere-2022-270-AC1
-
AC1: 'Reply on RC1', Sarah Garré, 25 Jul 2022
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RC2: 'Comment on egusphere-2022-270', Anonymous Referee #2, 23 Jun 2022
The topic of this review is interesting and covers a necessary research line. Authors have made a huge work collecting data from literature. The list of topics and cases is really huge, and the length of the manuscript is large. However, and after reading the manuscript, I have the feeling that I have not read anything new, or the new content has not been highlighted enough. Everything is known and expected. It is true that Figure 5 is valuable and could be appreciated by potential readers, but I cannot find the new content that any publication has to include. Several aspects should be addressed, namely:
- Authors have said that the aim of this review is to evaluate “the impacts of soil and crop management practices on soil properties and processes and the various ecosystem services and functions delivered by soil” and “these analyses with respect to the water regulation functions that are relevant for climate change adaptation in Europe”. However, no information is provided any the potential scenarios of climate change in Europe. For sure, adaptation will be different depending on the magnitude of climate change. I don’t think that this review is focussed on adaptation to climate change.
- Abstract. Authors have made a good job summarizing all sections of the manuscript. However, I miss the novel aspect of this review. In my opinion, the usefulness of a review of published meta-analysis is the emergence of new aspects that cannot be observed by the individualized analysis of each study. Therefore, I encourage authors to include in the abstract the actual contribution of this review: Where is the novelty?
- Section 2. Authors have included three sub-sections, namely: Literature search, Quality assessment, and Redundancy, but there is no information about the statistical analysis of the extracted information. Before showing the results, authors have to explain in detail, in a new sub-section, what they did with the data and information that they extracted from the selected literature. In my opinion, in a review study, there are 3 main aspects: I) what is the gap that you want to fill in; II) data mining; and III) methods and techniques to analyse the extracted information. Please, improve your manuscript taking into account these three aspects.
- L.154: Please, provide arguments (e.g. references) to support the comment that macroporosity should be strongly correlated with soil water infiltration.
Citation: https://doi.org/10.5194/egusphere-2022-270-RC2 -
AC2: 'Reply on RC2', Sarah Garré, 25 Jul 2022
As a review, it is inevitable that our paper summarizes what may be already quite well known for many readers, to a greater or lesser extent. Nevertheless, we feel that our paper provides an in-depth and comprehensive synthesis that is currently lacking. In this respect, our analysis, which is summarized in figure 5, has clearly identified strong areas of consensus, which should help to highlight research questions which may no longer require any further work!
Our synthesis has also highlighted important knowledge gaps related to the effects of management practices on the water regulation functions of soil. However we agree with the referee that we did not do a good enough job in highlighting these knowledge gaps, particularly in the abstract. In the revised version, we will re-write the second paragraph of the abstract to address this important omission.
We also agree with the referee that we did not outline potentially promising areas of future research that emerge from the knowledge gaps that we identified. In the conclusions section of the revised version of the paper, we will describe promising avenues of future research arising from our synthesis.
This will include recommendations to:
1. focus less on tillage effects per se and place more emphasis on the role and impact of traffic compaction in contrasting soil management systems (e.g. no-till vs. conventional till)
2. manipulate precipitation inputs (via irrigation and drought shelters) at existing LTFE’s to investigate the consequences of soil/crop management systems for water regulation under climate change
3. calibrate soil-crop simulation models against experimental data from LTFE’s and then use them to extrapolate for future projected climates
We will re-name this final section “Conclusions and outlook”
Several aspects should be addressed, namely:
- Authors have said that the aim of this review is to evaluate “the impacts of soil and crop management practices on soil properties and processes and the various ecosystem services and functions delivered by soil” and “these analyses with respect to the water regulation functions that are relevant for climate change adaptation in Europe”. However, no information is provided any the potential scenarios of climate change in Europe. For sure, adaptation will be different depending on the magnitude of climate change. I don’t think that this review is focused on adaptation to climate change.
It would be impossible to provide potential scenarios for climate change in any great detail for the whole of Europe. However, we have indicated in general terms the kind of future climate scenario for Europe that we are addressing in our paper, namely a climate characterized by longer and more severe droughts as well as more frequent intense rainfall events. This is mentioned in the first sentence of the abstract (line 3) and in the first two sentences of the paper itself (lines 25-28).
We think the review is quite strongly focused on the potential for management practices to assist in climate change adaptation. To support this, we cite text from the paper below that specifically relates to differences in climate among the primary studies included in the meta-analyses:
Lines 204-207: “An increased proportion of perennial crops in the rotation and the presence of ground cover between the rows of perennial crops (e.g. in vineyards) increase soil infiltration and reduce surface runoff ….. These positive effects seem broadly similar regardless of climate (Xiong et al., 2018; Liu et al., 2021)”.
Lines 209-213: “Meta-analyses have shown that high grazing intensities result in significantly poorer soil physical quality, in terms of larger bulk densities (Byrnes et al., 2018) and reduced infiltration rates (deLonge and Basche, 2018; Basche and deLonge, 2019) as a result of compaction by animal trampling. These impacts of intensive grazing are similar irrespective of soil texture or climate, although they appear to be slightly larger in wetter climates (Byrnes et al., 2018; deLonge and Basche, 2018)”.
Lines 215-217: “for a combined dataset of 36 studies comprising both experimental and modelling studies, Meyer et al. (2019) found that cover crops reduced recharge by 27 mm/year on average with no apparent effects of climate, soil type or cropping system”.
Lines 229-233. “Shackleford et al. (2019) reported an average 7% reduction in cash crop yields for systems employing non-legume cover crops in dry Mediterranean climate conditions. Similarly, in a recent meta-analysis on cover crops grown in climates with less than 500 mm annual rainfall, Blanco-Canqui et al. (2022) found that cover crops decreased main crop yields in 38% of cases, with no effects found in 56% of cases and increased yields in 6% of cases”.
Lines 268-270: “Mondal et al. (2020) found no significant differences in stocks of soil organic carbon between NT and CT systems, while variations in response could not be attributed to either climate or soil type”.
Lines 271-277: “Sun et al. (2020) demonstrated significant effects of climate on the changes in organic carbon stocks observed under NT systems. In their global analysis, they found that soil C sequestration was enhanced in warmer and drier regions, while soils under no-till in colder and wetter climates were just as likely to lose soil C as gain C. These findings are supported by the regional-scale studies of Meurer et al. (2018) for boreo-temperate climates and Gonzalez-Sanchez et al. (2012) and Aguilera et al. (2013) for Mediterranean climates, although for vineyards, Payen et al. (2021) found larger topsoil C sequestration in temperate climates than hot and dry climates”.
Lines 326-333: “Pittlekow et al. (2015) identified several reasons for variations in the yield response to no-till. Crop type was the most important, with no significant yield losses found under NT for oilseed, cotton and legume crops, while the yields of cereals and root crops were on average ca. 5% and 20% smaller respectively. In accordance with the results of the meta-analyses on stocks of soil organic
carbon discussed earlier, Pittlekow et al. (2015) and Sun et al. (2020) also found climate to be a significant factor, with no significant yield losses for no-till systems under rain-fed conditions in dry climates. In contrast, Peixoto et al. (2020) showed that occasional tillage increased crop yields compared with NT in dry regions and in soils with limited water retention capacity and availability, presumably by alleviating soil compaction and improving rooting”.
- Abstract. Authors have made a good job summarizing all sections of the manuscript. However, I miss the novel aspect of this review. In my opinion, the usefulness of a review of published meta-analysis is the emergence of new aspects that cannot be observed by the individualized analysis of each study. Therefore, I encourage authors to include in the abstract the actual contribution of this review: Where is the novelty?
We agree. Please see our response to the first comment from referee 2.
- Section 2. Authors have included three sub-sections, namely: Literature search, Quality assessment, and Redundancy, but there is no information about the statistical analysis of the extracted information. Before showing the results, authors have to explain in detail, in a new sub-section, what they did with the data and information that they extracted from the selected literature. In my opinion, in a review study, there are 3 main aspects: I) what is the gap that you want to fill in; II) data mining; and III) methods and techniques to analyse the extracted information. Please, improve your manuscript taking into account these three aspects.
We don’t actually do any statistical analysis of the information extracted from the meta-analyses (this is not really possible because only half of them included the raw data, as we mentioned at line 114)
Instead, we synthesized the results of published meta-analyses in a qualitative way, in order to highlight areas of agreement and consensus as well as gaps in knowledge and synergies/trade-offs. This was described in the paper, but we will try to further clarify our approach in the revised version.
We suspect that one reason for this misunderstanding concerning our methodology may have been that the heading of section 2.1 (“Literature search”) was inadequate. We will change the heading to “Literature search and information extraction”.
- L.154: Please, provide arguments (e.g. references) to support the comment that macroporosity should be strongly correlated with soil water infiltration.
Yes, we will cite these three review articles to support this statement:
Beven, K., Germann, P. 1982. Macropores and water flow in soils. Water Resources Research, 18, 1311-1325.
Lee, K., Foster, R. 1991. Soil fauna and soil structure. Aust. J. Soil Res., 29, 745-775.
Jarvis, N. 2007. A review of non-equilibrium water flow and solute transport in soil macropores: principles, controlling factors and consequences for water quality. European Journal of Soil Science, 58, 523-546.
Citation: https://doi.org/10.5194/egusphere-2022-270-AC2
-
AC2: 'Reply on RC2', Sarah Garré, 25 Jul 2022
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-270', Anonymous Referee #1, 10 Jun 2022
I appreciated the opportunity to review this manuscript. The authors present a well written, easy to read synthesis that outlines the knowns and knowledge gaps around a complex topic. I commend them for finding ways to simply visualize a number of concepts -- different agricultural practices related to sustainable agriculture and their impacts on various components of water regulation. I would encourage the authors to consider a few additions to clarify their methods and results.
The statement in the methods (lines 109-110) is quite brief in regards to how data was extracted from the meta-analyses. If I am following correctly it appears the authors visually from graphs or quantiatively from tables if effect sizes were significnatly above zero, below zero or were not different from zero, and then counted the n=value from these studies. It is not entirely clear to me how effect size is counted. Is this one per study (i.e. one effect size per MA?) or the total in the studies that were combined, and therefore 1 effect size = 1 field site embedded within one meta-analysis? I believe it is the latter. I encourage the authors to clarify. I also encourage the authors to consider if the lanugage "increase, decrease, no effect" is the same as "positive, neutral, negative". The latter have a connotation that is assumed by the reader, while the former are (in my opinion) more descriptive of the actual effects. For example, a decrease in runoff, while "negative" in nature, could be perceived as a positive effect of a management practice.
Although I found the manuscript generally easy to read and follow, I believe that the short intro and methods section are incongruent with the very long results & discussion. I encourage the authors to review and look for opportunities to be more concise. For example the discussion of tillage is quite lengthy, and although it is interesting to cover some elements of yield impacts, tradeoffs, etc. I am not sure that lenghty discussion as to the paper. And further, although the introduction discusses/focuses on conservation agriculture, the practices outlined in the paper are far broader in scope. I encourage the authors to consider a slight reframing of why specific practices were selected to focus on in this analysis. I do appreciate that the selection was broad, as it allows for a quick visualization/comparison of what properties and practices are more widely studies, but again think this decision needs more clarification.
I disagree with the authors final assessment in line 534 that continuous living cover reductions in SWS/recharge will outweigh increases due to carbon sequestration. While there may be concern of water limitations in drier climates, I do not believe the evidence presented supports this perception as there are few studies that look directly at this effect (judging by the gaps in evaporation and water content associated with the cropping systems practices). The benefits discussed in terms of soil physical improvements, plus benefits from carbon, with the uncertainties of rainfall variability and increases in precipitation in many places, even semiarid regions, make this assertion one that deserves more attention.
There is a small typo on line 112 - believe the first word in the sentence should be "We..."
Citation: https://doi.org/10.5194/egusphere-2022-270-RC1 -
AC1: 'Reply on RC1', Sarah Garré, 25 Jul 2022
The statement in the methods (lines 109-110) is quite brief in regards to how data was extracted from the meta-analyses. If I am following correctly it appears the authors visually from graphs or quantitatively from tables if effect sizes were significantly above zero, below zero or were not different from zero, and then counted the n=value from these studies. It is not entirely clear to me how effect size is counted. Is this one per study (i.e. one effect size per MA?) or the total in the studies that were combined, and therefore 1 effect size = 1 field site embedded within one meta-analysis? I believe it is the latter. I encourage the authors to clarify.
The number reported at line 108 is the total number of overall (average) effects sizes (i.e. the number of overall effects sizes for all combinations of management practices and target variables reported among all MA’s included in our analysis. We will clarify this.
I also encourage the authors to consider if the language "increase, decrease, no effect" is the same as "positive, neutral, negative". The latter have a connotation that is assumed by the reader, while the former are (in my opinion) more descriptive of the actual effects. For example, a decrease in runoff, while "negative" in nature, could be perceived as a positive effect of a management practice.
Yes, we did consider this aspect. The direction of the effect sizes reported in the paper are purely statistical and therefore have no connotation of value. We decided to report the effects in a statistical sense, because in some instances it’s not clear whether an effect would be beneficial or detrimental.
It was noted briefly in the caption to figure 5 (line 163) that the effects are statistical, but we will also make this clear in the text in the revised version of the paper.
We will also add the following information more clearly on how the graph was constructed:
To build Figure 5, we used a qualitative approach. From the figure reported in the meta-analyses, the overall effect size was extracted qualitatively. This means that if the average log response ratio and the entirely of 95% confidence interval was larger than 0 (so a response ratio of 1, 0 in log scale), it was considered as positive. The word "positive" here refers to the sign of the overall response ratio on a log scale. If some of the confidence interval overlapped 0, a "neutral" effect was chosen. If all confidence intervals were smaller than 0, the overall effect was considered as "negative". For all overall effects retrieved, the number of individual effect sizes used to compute the overall effect was also collected. For a given pair of practice and soil parameters, a pie chart representing the overall effects as a proportion of the number of individual effect sizes they summarised, is represented. There are situations where several meta-analyses can have information on the same pair, which can lead to pie charts with multiple colours. For instance, if a MA1 has a positive overall effect from 25 individual effect sizes and MA2 has a negative overall effect from 75 individual effect sizes, the pie chart will be one quarter orange (positive) and three quarters blue (negative). Note that that these proportions are qualitative and not quantitative. Indeed, we do not have the information on whether the individual effect size is positive, negative or neutral, but we only interpret the overall effect reported in the meta-analysis. The same figure with individual effect size would give other proportions (=quantitative approach). However, the trends between the qualitative and the quantitative approach will be similar. Several meta-analysis can also contain information about the same primary studies. This is shown in the redundancy analysis later.
Although I found the manuscript generally easy to read and follow, I believe that the short intro and methods section are incongruent with the very long results & discussion. I encourage the authors to review and look for opportunities to be more concise. For example the discussion of tillage is quite lengthy, and although it is interesting to cover some elements of yield impacts, tradeoffs, etc. I am not sure that lenghty discussion as to the paper. And further, although the introduction discusses/focuses on conservation agriculture, the practices outlined in the paper are far broader in scope. I encourage the authors to consider a slight reframing of why specific practices were selected to focus on in this analysis. I do appreciate that the selection was broad, as it allows for a quick visualization/comparison of what properties and practices are more widely studies, but again think this decision needs more clarification.
Yes, we agree. We did mention the terms climate-smart and regenerative agriculture in the introduction at lines 40-43. In the revised version, we will make it clearer that our synthesis is not exclusively focused on conservation agriculture.
I disagree with the authors final assessment in line 534 that continuous living cover reductions in SWS/recharge will outweigh increases due to carbon sequestration. While there may be concern of water limitations in drier climates, I do not believe the evidence presented supports this perception as there are few studies that look directly at this effect (judging by the gaps in evaporation and water content associated with the cropping systems practices). The benefits discussed in terms of soil physical improvements, plus benefits from carbon, with the uncertainties of rainfall variability and increases in precipitation in many places, even semiarid regions, make this assertion one that deserves more attention.
Yes, we agree. We will modify this statement to say that although there is some cause for concern, there is currently little empirical evidence that would allow us to draw any firm conclusions, and that more research is therefore needed.
There is a small typo on line 112 - believe the first word in the sentence should be "We..."
Thanks. We will correct this
Citation: https://doi.org/10.5194/egusphere-2022-270-AC1
-
AC1: 'Reply on RC1', Sarah Garré, 25 Jul 2022
-
RC2: 'Comment on egusphere-2022-270', Anonymous Referee #2, 23 Jun 2022
The topic of this review is interesting and covers a necessary research line. Authors have made a huge work collecting data from literature. The list of topics and cases is really huge, and the length of the manuscript is large. However, and after reading the manuscript, I have the feeling that I have not read anything new, or the new content has not been highlighted enough. Everything is known and expected. It is true that Figure 5 is valuable and could be appreciated by potential readers, but I cannot find the new content that any publication has to include. Several aspects should be addressed, namely:
- Authors have said that the aim of this review is to evaluate “the impacts of soil and crop management practices on soil properties and processes and the various ecosystem services and functions delivered by soil” and “these analyses with respect to the water regulation functions that are relevant for climate change adaptation in Europe”. However, no information is provided any the potential scenarios of climate change in Europe. For sure, adaptation will be different depending on the magnitude of climate change. I don’t think that this review is focussed on adaptation to climate change.
- Abstract. Authors have made a good job summarizing all sections of the manuscript. However, I miss the novel aspect of this review. In my opinion, the usefulness of a review of published meta-analysis is the emergence of new aspects that cannot be observed by the individualized analysis of each study. Therefore, I encourage authors to include in the abstract the actual contribution of this review: Where is the novelty?
- Section 2. Authors have included three sub-sections, namely: Literature search, Quality assessment, and Redundancy, but there is no information about the statistical analysis of the extracted information. Before showing the results, authors have to explain in detail, in a new sub-section, what they did with the data and information that they extracted from the selected literature. In my opinion, in a review study, there are 3 main aspects: I) what is the gap that you want to fill in; II) data mining; and III) methods and techniques to analyse the extracted information. Please, improve your manuscript taking into account these three aspects.
- L.154: Please, provide arguments (e.g. references) to support the comment that macroporosity should be strongly correlated with soil water infiltration.
Citation: https://doi.org/10.5194/egusphere-2022-270-RC2 -
AC2: 'Reply on RC2', Sarah Garré, 25 Jul 2022
As a review, it is inevitable that our paper summarizes what may be already quite well known for many readers, to a greater or lesser extent. Nevertheless, we feel that our paper provides an in-depth and comprehensive synthesis that is currently lacking. In this respect, our analysis, which is summarized in figure 5, has clearly identified strong areas of consensus, which should help to highlight research questions which may no longer require any further work!
Our synthesis has also highlighted important knowledge gaps related to the effects of management practices on the water regulation functions of soil. However we agree with the referee that we did not do a good enough job in highlighting these knowledge gaps, particularly in the abstract. In the revised version, we will re-write the second paragraph of the abstract to address this important omission.
We also agree with the referee that we did not outline potentially promising areas of future research that emerge from the knowledge gaps that we identified. In the conclusions section of the revised version of the paper, we will describe promising avenues of future research arising from our synthesis.
This will include recommendations to:
1. focus less on tillage effects per se and place more emphasis on the role and impact of traffic compaction in contrasting soil management systems (e.g. no-till vs. conventional till)
2. manipulate precipitation inputs (via irrigation and drought shelters) at existing LTFE’s to investigate the consequences of soil/crop management systems for water regulation under climate change
3. calibrate soil-crop simulation models against experimental data from LTFE’s and then use them to extrapolate for future projected climates
We will re-name this final section “Conclusions and outlook”
Several aspects should be addressed, namely:
- Authors have said that the aim of this review is to evaluate “the impacts of soil and crop management practices on soil properties and processes and the various ecosystem services and functions delivered by soil” and “these analyses with respect to the water regulation functions that are relevant for climate change adaptation in Europe”. However, no information is provided any the potential scenarios of climate change in Europe. For sure, adaptation will be different depending on the magnitude of climate change. I don’t think that this review is focused on adaptation to climate change.
It would be impossible to provide potential scenarios for climate change in any great detail for the whole of Europe. However, we have indicated in general terms the kind of future climate scenario for Europe that we are addressing in our paper, namely a climate characterized by longer and more severe droughts as well as more frequent intense rainfall events. This is mentioned in the first sentence of the abstract (line 3) and in the first two sentences of the paper itself (lines 25-28).
We think the review is quite strongly focused on the potential for management practices to assist in climate change adaptation. To support this, we cite text from the paper below that specifically relates to differences in climate among the primary studies included in the meta-analyses:
Lines 204-207: “An increased proportion of perennial crops in the rotation and the presence of ground cover between the rows of perennial crops (e.g. in vineyards) increase soil infiltration and reduce surface runoff ….. These positive effects seem broadly similar regardless of climate (Xiong et al., 2018; Liu et al., 2021)”.
Lines 209-213: “Meta-analyses have shown that high grazing intensities result in significantly poorer soil physical quality, in terms of larger bulk densities (Byrnes et al., 2018) and reduced infiltration rates (deLonge and Basche, 2018; Basche and deLonge, 2019) as a result of compaction by animal trampling. These impacts of intensive grazing are similar irrespective of soil texture or climate, although they appear to be slightly larger in wetter climates (Byrnes et al., 2018; deLonge and Basche, 2018)”.
Lines 215-217: “for a combined dataset of 36 studies comprising both experimental and modelling studies, Meyer et al. (2019) found that cover crops reduced recharge by 27 mm/year on average with no apparent effects of climate, soil type or cropping system”.
Lines 229-233. “Shackleford et al. (2019) reported an average 7% reduction in cash crop yields for systems employing non-legume cover crops in dry Mediterranean climate conditions. Similarly, in a recent meta-analysis on cover crops grown in climates with less than 500 mm annual rainfall, Blanco-Canqui et al. (2022) found that cover crops decreased main crop yields in 38% of cases, with no effects found in 56% of cases and increased yields in 6% of cases”.
Lines 268-270: “Mondal et al. (2020) found no significant differences in stocks of soil organic carbon between NT and CT systems, while variations in response could not be attributed to either climate or soil type”.
Lines 271-277: “Sun et al. (2020) demonstrated significant effects of climate on the changes in organic carbon stocks observed under NT systems. In their global analysis, they found that soil C sequestration was enhanced in warmer and drier regions, while soils under no-till in colder and wetter climates were just as likely to lose soil C as gain C. These findings are supported by the regional-scale studies of Meurer et al. (2018) for boreo-temperate climates and Gonzalez-Sanchez et al. (2012) and Aguilera et al. (2013) for Mediterranean climates, although for vineyards, Payen et al. (2021) found larger topsoil C sequestration in temperate climates than hot and dry climates”.
Lines 326-333: “Pittlekow et al. (2015) identified several reasons for variations in the yield response to no-till. Crop type was the most important, with no significant yield losses found under NT for oilseed, cotton and legume crops, while the yields of cereals and root crops were on average ca. 5% and 20% smaller respectively. In accordance with the results of the meta-analyses on stocks of soil organic
carbon discussed earlier, Pittlekow et al. (2015) and Sun et al. (2020) also found climate to be a significant factor, with no significant yield losses for no-till systems under rain-fed conditions in dry climates. In contrast, Peixoto et al. (2020) showed that occasional tillage increased crop yields compared with NT in dry regions and in soils with limited water retention capacity and availability, presumably by alleviating soil compaction and improving rooting”.
- Abstract. Authors have made a good job summarizing all sections of the manuscript. However, I miss the novel aspect of this review. In my opinion, the usefulness of a review of published meta-analysis is the emergence of new aspects that cannot be observed by the individualized analysis of each study. Therefore, I encourage authors to include in the abstract the actual contribution of this review: Where is the novelty?
We agree. Please see our response to the first comment from referee 2.
- Section 2. Authors have included three sub-sections, namely: Literature search, Quality assessment, and Redundancy, but there is no information about the statistical analysis of the extracted information. Before showing the results, authors have to explain in detail, in a new sub-section, what they did with the data and information that they extracted from the selected literature. In my opinion, in a review study, there are 3 main aspects: I) what is the gap that you want to fill in; II) data mining; and III) methods and techniques to analyse the extracted information. Please, improve your manuscript taking into account these three aspects.
We don’t actually do any statistical analysis of the information extracted from the meta-analyses (this is not really possible because only half of them included the raw data, as we mentioned at line 114)
Instead, we synthesized the results of published meta-analyses in a qualitative way, in order to highlight areas of agreement and consensus as well as gaps in knowledge and synergies/trade-offs. This was described in the paper, but we will try to further clarify our approach in the revised version.
We suspect that one reason for this misunderstanding concerning our methodology may have been that the heading of section 2.1 (“Literature search”) was inadequate. We will change the heading to “Literature search and information extraction”.
- L.154: Please, provide arguments (e.g. references) to support the comment that macroporosity should be strongly correlated with soil water infiltration.
Yes, we will cite these three review articles to support this statement:
Beven, K., Germann, P. 1982. Macropores and water flow in soils. Water Resources Research, 18, 1311-1325.
Lee, K., Foster, R. 1991. Soil fauna and soil structure. Aust. J. Soil Res., 29, 745-775.
Jarvis, N. 2007. A review of non-equilibrium water flow and solute transport in soil macropores: principles, controlling factors and consequences for water quality. European Journal of Soil Science, 58, 523-546.
Citation: https://doi.org/10.5194/egusphere-2022-270-AC2
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AC2: 'Reply on RC2', Sarah Garré, 25 Jul 2022
Peer review completion
Journal article(s) based on this preprint
Data sets
Supporting studies Guillaume Blanchy, Nicholas Jarvis https://github.com/climasoma/review-of-meta-analyses/tree/main/data/meta
Model code and software
Review of meta-analysis Guillaume Blanchy https://github.com/climasoma/review-of-meta-analyses/blob/main/notebooks/meta-graph.ipynb
Interactive computing environment
Redundancy analysis Guillaume Blanchy https://github.com/climasoma/review-of-meta-analyses/blob/main/notebooks/redundancy.ipynb
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Guillaume Blanchy
Gilberto Bragato
Claudia Di Bene
Mats Larsbo
Katharina Meurer
Sarah Garré
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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