Recurring Rolling/Crimping Effects on Termination Effectiveness of Iron Clay Pea and Pearl Millet Warm-Season Cover Crops

Round 1

Reviewer 1 Report

Recurring rolling/crimping effects on termination effectiveness 2 for iron clay pea and pearl millet warm season cover crops 

The Review Report 

Materials and Methods: 

• Show why you did not follow the same pattern (same planting age for the cover crop) for the three experiment (86, 91, and 101 days for iron clay peas) (72, 79, and 70 days for pearl millet) for growing seasons 2015, 2016, and 2017 respectively. Also show if this procedure affects or does affect the characteristics and the structures of the cover crops (biomass and plant height) which would the affects the performance of the termination machine. 

• You should show the methods that you followed in order to guarantee that you will get uniformity and even plant density through your three experiments growing seasons. Like use the same amount of seeds for the same area, the distribution of the seeds was evenly and etc. This important to ensure that your study have been done in the same circumstance. 

• How many plots did you study in your research? 

• For chlorophyll measurement, how many samples did you take for each plot? And how did distribute them thorough each plot? 

• Line 122: (termination rate were determined using several measurements) are these measurement at the same time? If yes show how many as mentioned above, if no show at which time did you take the measurements? 

• Move the paragraph from line 159 to line 161 till (random effects) to the first paragraph in the Materials and Methods 

• How did you choose your samples locations? In other words how did you distribute your samples in the studied area to ensure that you covered the total area accurately? 

The Results and Discussions: 

• Lines 169 to 171: how could you be sure that the differences of plant age have no effect on plant height and biomass? 

• Your results showed big variations in plant biomass. Did you calculate plant density (plant/m2)? It seems that you did not, but if you did it would be very clear to understand why there were big variations in the plant biomass. 

• Table 2: explain why the highest plant for Pearl Millet is not the heaviest one (190.7 cm/14038 kg/ha, and 222.2 cm/12230 kg/ha)? 

• Your results showed that the heaviest and highest plants were not connected with the heaviest rain (7916 kg/ha, 52.8 cm vs. 7036 kg/ha, 47.9 cm for Iron Clay Pea for the rain fall 347 mm vs. 457 mm, and 14038 kg/ha, and 190.7 cm vs. 12230 kg/ha, for Pearl Millet for rain fall 299 mm vs. 310 mm, except for the plant height for Pearl Millet for rain fall of 457 mm. Explain. 

• Line 233 to 234: (crimping was ineffective due to variations in the soil surface) why there were big variations in soil surface? Why you did not level the soil before planting?

Author Response

Dear Reviewer,

Thank you for providing valuable suggestions and comments to improve the manuscript.

Specific responses are listed below:

Materials and Methods: 

• Show why you did not follow the same pattern (same planting age for the cover crop) for the three experiment (86, 91, and 101 days for iron clay peas) (72, 79, and 70 days for pearl millet) for growing seasons 2015, 2016, and 2017 respectively. Also show if this procedure affects or does affect the characteristics and the structures of the cover crops (biomass and plant height) which would the affects the performance of the termination machine. 

On lines 268 -277 we added following paragraph:

This experiment was conducted under natural weather conditions in Alabama. The experimental area planted to cover crops was not irrigated, and cover crops growth was considered as dryland field testing conditions. Cover crop maturity is dependent solely on the weather conditions such as rainfall and temperature. In hot summer months rainfalls can provide a positive development of cover crops, but too much rainfall can be detrimental for the plant development and inhibits its growth and inability to obtain a right maturity for mechanical termination at the same period at each growing season. Also, high temperature with a lack of rainfall, can negatively affect cover crop growth, and obviously different weather conditions at each growing season influenced different growing periods from planting to reaching full maturity of the cover crops. Therefore, the length of growing cover crops from planting to reaching full maturity for mechanical termination does not affect mechanical termination using rolling/crimping technology.

• You should show the methods that you followed in order to guarantee that you will get uniformity and even plant density through your three experiments growing seasons. Like use the same amount of seeds for the same area, the distribution of the seeds was evenly and etc. This important to ensure that your study have been done in the same circumstance.  

On lines: 121 - 126 we added following information:

Each experimental plot area was 465 sq. m (0.0465 ha.) and seeds for both cover crops were broadcast in each growing season to the entire plot area 5.9 kg for iron clay pea and 3.2 kg for pearl millet utilizing a chest spreader for all three seasons. Planting rates per hectare were 127 kg/ha for iron clay peas and 68 kg/ha for pearl millet. Then seeds were tilled in (incorporated) and packed in with mesh (basket) roller to provide a level surface and good seed to soil contact.

• How many plots did you study in your research? 

On lines 126-127 we added a sentence:

A total of 16 plots with dimensions of 6.1 m long by 1.8 m wide were comprised in the field experiment.

• For chlorophyll measurement, how many samples did you take for each plot? And how did distribute them thorough each plot? 

On lines 166 – 174 we added a paragraph: Three chlorophyll measurements were taken of the leaves in each plot. The first measurement was collected close to the centerline of the plot (lengthwise) was done approximately 0.5 m from the plot edge, the second was obtained about 2.0 meters from the first one, and the third one was taken also 2.0 m from the second one (about 0.5 m from the end of the plot). The leaf selection was based on a representative sample chosen randomly in proximity of the plot centerline. Average value from three samples was reported for each plot. Termination rate measurements were taken at the same time going through the 16 plots completing 48 measurements. All 48 measurements required approximately one hour to complete.

• Line 122: (termination rate were determined using several measurements) are these measurement at the same time? If yes show how many as mentioned above, if no show at which time did you take the measurements? 

On lines 175-100 we added a clarification:

Quantitative values for plant condition at 100% termination rate were determined with 10 measurements of a randomly selected cover crop leaf (10 leaves) using the chlorophyll meter SPAD 502 along by visual observations confirming that the plant tissue was dead. Termination assessment using SPAD 502 started with 10 leaves of each cover crop when it was green (0% termination). Then every day, as cover crops changed their appearance (color and moisture) these measurements were repeated. Termination rate measurements were taken at the same time going through the 16 plots completing 48 measurements. All 48 measurements required approximately one hour to complete.

• Move the paragraph from line 159 to line 161 till (random effects) to the first paragraph in the Materials and Methods.

As suggested by the reviewer, the paragraph from line 159 – 161 was moved to lines 117 – 120. 

• How did you choose your samples locations? In other words how did you distribute your samples in the studied area to ensure that you covered the total area accurately? 

 On lines 198 – 202 we added requested information:

For the cover crops termination assessment and for volumetric soil moisture content (VMC) measurement, three measurements per each plot were completed. Having 4 replications per each treatment, a total of 12 measurements for each treatment were obtained. Then the average value from three measurements for termination rate and VMC were reported for each plot.

The Results and Discussions: 

• Lines 169 to 171: how could you be sure that the differences of plant age have no effect on plant height and biomass? 

We already addressed this issue in pervious response explaining different weather conditions effects on cover crop growth.

• Your results showed big variations in plant biomass. Did you calculate plant density (plant/m2)? It seems that you did not, but if you did it would be very clear to understand why there were big variations in the plant biomass.

We did not calculate plant density in number of plants per sq. meter. We obtained cover crop biomass sample (one sample from each plot) using a stainless-steel frame measuring 0.5 m x 05 m (0.25 sq. meter area) and clipped all plants at ground level from this area. Then we reported the dry biomass per each plot (4 replications for each rolling treatment) expressed in kg per hectare. Variation of cover crop biomass is solely related to weather conditions at each of three growing seasons.

• Table 2: explain why the highest plant for Pearl Millet is not the heaviest one (190.7 cm/14038 kg/ha, and 222.2 cm/12230 kg/ha)? 

On lines 230 – 236 we explained:

Results indicate a proportional relationship does not always exist between the length of the plant and its weight exists. For example, research from [26] presents results from the evaluation of nine different pearl millet varieties in which plant height at maturity do not coincide with the highest biomass production.  Similar results for [27] also show variation between sorghum height and dry matter yield. In fact, shorter plants can develop stems that have a larger diameter than the tallest plants. 

We need to emphasize that in our study, behavior of two cover crop selected might be the same, but studying this relationship is out of scope of this experiment and follow an extensive knowledge in plant physiology. The main focus of this experiment was to evaluate our patented equipment (2-stage roller/crimper) that was developed to terminate summer cover crops mechanically, especially focusing on organic no-till systems with cover crops, where commercial herbicides are not permitted to use. 

• Your results showed that the heaviest and highest plants were not connected with the heaviest rain (7916 kg/ha, 52.8 cm vs. 7036 kg/ha, 47.9 cm for Iron Clay Pea for the rain fall 347 mm vs. 457 mm, and 14038 kg/ha, and 190.7 cm vs. 12230 kg/ha, for Pearl Millet for rain fall 299 mm vs. 310 mm, except for the plant height for Pearl Millet for rain fall of 457 mm. Explain. 

Planting conditions for iron clay peas were quite different in 2015 and 2017. In 2015, one week before planting iron clay peas, 53 mm of rainfall occurred with no rainfall 4 days before planting. In contrast, in 2017, one week before planting iron clay peas, 74 mm more rainfall occurred compared to 2015, and there was only one day without rainfall before planting iron clay peas. Therefore, soil moisture in the sandy loam soil in 2017 was already higher on the day of planting than in 2015. Also, in 2015, 29 days received rainfall out of a total of 86 days between planting and termination for a total of 347 mm of precipitation. In contrast for 2017, 43 days received rainfall out of a total of 102 days between planting and termination totaling 457 mm of precipitation. Based on these data, more rainfall amounts in 2017 inhibited growth of iron clay peas rather than helping biomass production, as this plant is very drought resistant and does not require a considerably higher rainfall amounts for its optimum growth. Since both cover crops were planted on the same day at each growing season, these soil conditions were also applied to pearl millet cover crop: 25 days with rainfall out of 71 total days from planting to termination in 2015 and 34 days with rainfall in 2017. Pearl millet is also drought resistant plant and too much rainfall might inhibit its vegetative growth.

• Line 233 to 234: (crimping was ineffective due to variations in the soil surface) why there were big variations in soil surface? Why you did not level the soil before planting?

At planting cover crops, each soil was tilled and leveled with basket roller to provide a uniform soil surface. With elapsed time, and rainfall events, soil surface naturally consolidates, which causes voids between soil surface and the roller’s crimping bar across roller’s 1.8 m working width. Stems of iron clay peas are relatively small and these are flattened by the roller’s smooth drum, but because of voids between soil surface and the crimping bar, these stems were not effectively crimped as the rigid 1.8 m wide steel bar does not flex to conform to the soil surface.

Reviewer 2 Report

The authors examined the efficacy of termination rates for iron clay peas planted on sandy loam soil and pearl millet planted on clay soil, considering various rolling/crimping frequencies in regions of the southern United States prone to intense storms. This research topic is both intriguing and valuable. However, certain aspects could be refined to enhance clarity and contextualization.

Lines 15-16: The significance of the termination rate disparities across rolling frequencies requires further exploration. What factors could be responsible for the elevated success rate observed with triple rolling? A comprehensive discussion of potential underlying mechanisms, encompassing crop physiology, soil disruption, and mechanical influences, would enrich the analysis.

Lines 19-20: Could you elaborate on whether the mulching effect is solely accountable for this outcome, or if other factors contribute to it?

Taylor (1963) highlighted the relevance of the 2.0 MPa threshold for cotton root penetration resistance. Nonetheless, there is insufficient evidence to posit that this same threshold applies as a root-restriction determinant for these two cover crops in question. Furthermore, the data pertinent to root systems within the soil profile is absent.

Given the authors' mention of the farming community's concerns about the potential soil compaction resulting from recurrent rolling/crimping over the same cover crop, the study's conclusion that soil compaction does not occur is noteworthy. It would be beneficial for the authors to delve into the broader implications of these findings for farmers and practitioners. How might these results inform decisions regarding cover crop selection and specific termination practices? A more comprehensive discussion of practical relevance and benefits is recommended.

Further elaboration on the rationale behind selecting iron clay peas and pearl millet as cover crops, and how their selection aligns with the study's objectives, would provide valuable context.

Although the methodology is detailed, additional information about the design and implementation of the roller/crimper system would enhance comprehension.

Given the considerable number of tables within the manuscript, a consolidation is advisable. Specifically, combining tables related to the two cover crops into a singular line graph would bolster clarity and conciseness.

Rather than presenting results on an annual basis, synthesizing patterns and distilling key findings is crucial.

While there is a wealth of cover crop research available, the literature cited in this manuscript appears to be notably dated, based on my current knowledge.

Author Response

Dear Reviewer,

Thank you for providing valuable suggestions to improve the manuscript.

Specific responses are listed below:

The authors examined the efficacy of termination rates for iron clay peas planted on sandy loam soil and pearl millet planted on clay soil, considering various rolling/crimping frequencies in regions of the southern United States prone to intense storms. This research topic is both intriguing and valuable. However, certain aspects could be refined to enhance clarity and contextualization.

Lines 15-16: The significance of the termination rate disparities across rolling frequencies requires further exploration. What factors could be responsible for the elevated success rate observed with triple rolling? A comprehensive discussion of potential underlying mechanisms, encompassing crop physiology, soil disruption, and mechanical influences, would enrich the analysis.

Answer regarding lines 15-16: An extensive discussion was added on lines 98 – 107 describing rolling principles and what happened with the cover crop plant during the rolling/crimping action. Below is the addition of this discussion:

In addition, on lines 382- 397 the following statements were added addressing triple crimping action of cover crop over the same cover crop area explaining crop physiology, soil disruption due to mechanical forces:     

Lines 395-410: Overall, rolling/crimping three times over the same cover crop area resulted in higher termination rates for both cover crops compared to rolling once or twice. These results can be explained by working principle of the two-stage roller/crimper. Since mechanical termination of cover crop by the roller/crimper is based on crushing stems at equal intervals against a firm soil, it restricts nutrients and water flow from roots across the plant length causing accelerated plant death. With rolling/crimping three times, this process repeats itself three times and triples number of injuries sustained by the cover crop that critically damages the stem tissue without severing the whole plant. For the effective crimping of cover crop, firmness of soil surface, that is solely dependent on the soil moisture, must be much greater compared to the softer green cover crop tissue. Based on previous research an optimum soil moisture to provide soil firmness is between 8% and 9% [7, 8]. Since the crimping bar’s downward force crimps flattened cover crops, this force dissipates on flattened cover crop layer and does not damage the firm soil structure. In contrast, if the soil is wet, soil firmness is substantially diminished, soil structure is damaged (disrupted) [29]. and crimping is ineffective (cover crop stems are imprinted into the soft soil by steel crimping bars).

Following reference was added:

Magdoff, F. and Van Es, H. 2021. Building Soils for Better Crops. Ecological Management for Healthy Soils. Chapter 15: Addressing Compaction. Fourth Edition by Handbook Series Book 10. Published by the Sustainable Agriculture Research and Education (SARE) program, with funding from the National Institute of Food and Agriculture, U.S. Department of Agriculture.

https://www.sare.org/wp-content/uploads/Building-Soils-for-Better-Crops.pdf

Lines 19-20: Could you elaborate on whether the mulching effect is solely accountable for this outcome, or if other factors contribute to it?

On lines 19-21, we added further principle of mulching effect: “Rolling provided higher soil-water conservation compared with the non-rolled control due the cover crop mulch layer blocking sunlight which keeps the soil surface cooler and prevent water evaporation.”

In addition, in introduction (lines 45 to 55) we added additional information regarding the mulching principle and benefits.

In agroecosystems where water for crop production is in short supply, flattened cover crops can be left on the soil surface and used as a mulch to conserve water by shading and cooling the soil surface. This reduces the evaporation of water for the soil surface. Mulching is a technique that involves covering the soil with a layer of organic material (cover crop residue). Mulching has several benefits including retaining moisture by preventing water evaporation, suppressing weeds by blocking sun and not allowing weed seeds to germinate, improving soil health by adding nutrients and organic matter to the soil, preventing soil erosion by reducing the impact of raindrops on the soil surface, and regulating soil temperature by keeping the soil cooler in hot weather conditions in Alabama.  

Taylor (1963) highlighted the relevance of the 2.0 MPa threshold for cotton root penetration resistance. Nonetheless, there is insufficient evidence to posit that this same threshold applies as a root-restriction determinant for these two cover crops in question. Furthermore, the data pertinent to root systems within the soil profile is absent.

Since cotton has a commercial value as a commodity, it has been fully examined with respect to studying detrimental effects of growth from soil compaction. Therefore, this threshold is mentioned when dealing with soil compaction issues. There has not been such research conducted for cover crops. We selected two summer cover crops that can effectively manage soil compaction.  Pearl millet has high root density, root dry matter, and vegetative vigor, and is especially well suited to break up compacted soil. Like other grass cover crops (sorghum for example), it develops rapidly, covers the soil surface, and has an extensive, fibrous root system. Iron clay pea is heat and drought tolerant legume that can also protect soil from compaction.

Given the authors' mention of the farming community's concerns about the potential soil compaction resulting from recurrent rolling/crimping over the same cover crop, the study's conclusion that soil compaction does not occur is noteworthy. It would be beneficial for the authors to delve into the broader implications of these findings for farmers and practitioners. How might these results inform decisions regarding cover crop selection and specific termination practices? A more comprehensive discussion of practical relevance and benefits is recommended. 

On pages 608 – 618, we added information regarding practical relevance of this research:

Based on results from this experiment, summer cover crops termination rates vastly increased with rolling/crimping twice or three times over the same cover crop area compared with a single pass. Such findings are important for organic systems with cover crops, where only mechanical termination such rolling/crimping can be utilized, as terminating cover crops with commercial herbicides is prohibited. Another important benefit from flattening and crimping cover crop against soil surface is conserving soil water through mulching barrier which resulted in higher volumetric soil moisture due to decreased soil water evaporation. Notably, rolling/crimping twice or three times over the same cover crop area, did not cause soil compaction. Changes in soil strength was not affected by rolling treatments but was depended on changes in soil moisture.

Further elaboration on the rationale behind selecting iron clay peas and pearl millet as cover crops, and how their selection aligns with the study's objectives, would provide valuable context.

On lines 97 – 106 we added following paragraph:

Iron Clay Pea has been used in Alabama as a popular summer legume cover crop having excellent soil erosion and weed control. It also provides good protection from soil compaction, and it is a heat and drought resistant plant during hot summer months, but does not perform well in excessively wet soil [16, 17]. In addition, this legume can pro-duce 110 to 160 kg nitrogen ha^-1 [18, 19]. Pearl millet is a warm-season annual bunchgrass with height from 1.8 m to 2.1 m that scavenges nitrogen, protects from soil erosion, and suppresses weeds in the summer. This plant is well suited to grow on many different soils, including clay soils, as it can break up compacted soil and develops a deep root system that can survive under water shortage [20, 21, 22].

We supported these statements by following references (16-22):

16. Southern Cover Crop Council. 2018 Cover Crop Information Sheet Cowpea (Vigna unguiculata).

https://southerncovercrops.org/wp-content/uploads/2018/10/Cowpeas-Row-Crop-CP.pdf#:~:text=Cowpeas%20have%20long%20been%20grown%20in%20the%20Southern,do%20not%20do%20well%20in%20very%20wet%20conditions

17. Cover Crop/Forage Tech Sheet. 2018. Iron Clay Cowpeas Summer. Annual Cover Crop. King’s AgriSeeds.

https://www.kingsagriseeds.com/wp-content/uploads/2018/02/Iron-and-Clay-Cowpeas.pdf

18. Smith, M. and Gamble, A. 2023. Cover crops for Alabama. 2023 Alabama Cooperative Extension System, ANR 2139. https://www.aces.edu/blog/topics/row-cover-crop-soils/cover-crops-for-alabama/
19. Sheahan, C.M. 2012. Plant guide for cowpea (Vigna unguiculata). USDA-Natural Resources Conservation Service, Cape May Plant Materials Center, Cape May, NJ. Published 06/2012.

https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_viun.pdf

20. Myers, R. 2018. Growing Millets for Grain, Forage or Cover Crop Use. Division of Plant Sciences. Extension University of Missouri. https://extension.missouri.edu/publications/g4164 Assessed September 15, 2023.
21. Managing cover crops Profitably. 2012. Handbook Series Book 9. Published by the Sustainable Agriculture Research and Education (SARE) program, with funding from the National Institute of Food and Agriculture, U.S. Department of Agriculture. Third Edition.
22. Sheahan, C.M. 2014. Plant guide for pearl millet (Pennisetum glaucum). USDA-Natural Resources Conservation Service, Cape May Plant Materials Center, Cape May, NJ. Published 08/2014.

https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_pegl2.pdf#:~:text=Nevertheless%2C%20Rosolem%20et%20al.%20%282004%29%20found%20that%20pearl,can%20be%20used%20as%20a%20good%20surface%20mulch 

Although the methodology is detailed, additional information about the design and implementation of the roller/crimper system would enhance comprehension.

On lines 129-138 additional information regarding roller design and implementation was provided in the manuscript:

Two-stage roller/crimper [24] comprises of two drums, with the first being a smooth drum that flattens cover crop on the soil surface, and the second drum with equally spaced crimping bars on drum’s circumference crimps stems and flattens cover crop. Crimping principle is based on applying vertical force generated by the weight of the drum to the cover crop against a firm soil surface. To increase the crimping effective-ness, the second drum assembly with crimping bars is also preloaded with two com-pression springs on each end of the drum. When the roller/crimper moves forward, springs are compressed and decompressed (due to advancing from one crimping bar to the next), and they release its kinetic energy as a downward force (perpendicular) to the laying down cover crop and causes injury (crushes tissue) to the cover crop at equal intervals.

Reference of this patented roller/crimper: 24. Kornecki, T.S. Multistage crop roller 2011; US Patent Number 7,987,917 B1.

Given the considerable number of tables within the manuscript, a consolidation is advisable. Specifically, combining tables related to the two cover crops into a singular line graph would bolster clarity and conciseness.

We carefully considered combining tables; however, this would require completely restructuring the manuscript. Having only a very limited time to do revisions, we decided not to merging data and presenting results as general patterns of this field experiment.  

Rather than presenting results on an annual basis, synthesizing patterns and distilling key findings is crucial.

Our statistical analysis clearly indicate that variable “YEAR’ was highly significant across all treatments. We considered rearranging results and changing tables; however variable year was highly significant across all treatments. Specifically, cover crop development was highly dependent on different weather conditions at each growing season. Therefore, we decided not to average results among three growing seasons as different reviewers asked to explain specific differences of treatments and variables at each growing season.

While there is a wealth of cover crop research available, the literature cited in this manuscript appears to be notably dated, based on my current knowledge.

We added 10 more citations to further strengthen the discussion in the manuscript.

Reviewer 3 Report

In this manuscript, the authors summarized and discussed the effects of number of rolling passes (rolling once, twice and three times over the same area) with a 2-stage roller/crimper on two warm season cover crop (iron clay peas and pearl millet) termination, volumetric soil moisture content, and soil compaction. This work provides new insights and data support for the management of summer cover crops in no-tillage systems. Some specific comments were below:

1.         In the introduction part, more updated references and recent findings could be added, and the novelty and research gap could be further addressed. Eg. the reason for choosing different cover crop, different soils.

2.         Some details could be provided in the materials and methods, such as the latitude and longitude information of the experiment, the seeding rate of the covered crops. the number of plants  measured for chlorophyll content in each plot, and brief description of methods to determine chlorophyll.

3.         Line184-186: For iron clay peas, the highest biomass in 2015 was attribute to rainfall. But the precipitation in 2017 was more than that in 2015, please further explain why? Similarly, for pearl millet, the biomass might not only be related to rainfall?

4.         Double-check the data of rolling twice treatment in Table5, 2016, the average termination rate in 0day was much lower than other treatments, but the analysis of variance showed no significant difference? Also the termination rate of rolling one treatment on 0DAR, 2017, which was twice higher than that under other treatments, but no difference? Check whether the letter next to 72.8 in Table 6 is an a or a b?

5.         Line256: Please further explain "vining nature of this cover crop".

6.         Line293 " 63.9 % " not " 69.3 % ".

7.         Soil properties have been mentioned many times in the discussion of soil water content and soil strength. For example, Line489-491, please specify? Is there any other soil properties data to support the discussion?

8.         The best management measure for warm season cover crops should be put forward in the conclusions.

Author Response

Dear Reviewer,

Thank you for providing valuable suggestions to improve the manuscript.

Specific responses are listed below:

In this manuscript, the authors summarized and discussed the effects of number of rolling passes (rolling once, twice and three times over the same area) with a 2-stage roller/crimper on two warm season cover crop (iron clay peas and pearl millet) termination, volumetric soil moisture content, and soil compaction. This work provides new insights and data support for the management of summer cover crops in no-tillage systems. Some specific comments were below:

1. In the introduction part, more updated references and recent findings could be added, and the novelty and research gap could be further addressed. the reason for choosing different cover crop, different soils.

On lines 97 – 106 we added following paragraph:

Iron Clay Pea has been used in Alabama as a popular summer legume cover crop having excellent soil erosion and weed control. It also provides good protection from soil compaction, and it is a heat and drought resistant plant during hot summer months but does not perform well in excessively wet soil [16, 17]. In addition, this legume can produce 110 to 160 kg nitrogen ha-1 [18, 19]. Pearl millet is a warm-season annual bunchgrass with height from 1.8 m to 2.1 m that scavenges nitrogen, protects from soil erosion, and suppresses weeds in the summer. This plant is well suited to grow on many different soils, including clay soils, as it can break up compacted soil and develops a deep root system that can survive under water shortage [20, 21, 22]. We supported these statements by following references:

16. Southern Cover Crop Council. 2018 Cover Crop Information Sheet Cowpea (Vigna unguiculata).

https://southerncovercrops.org/wp-content/uploads/2018/10/Cowpeas-Row-Crop-CP.pdf#:~:text=Cowpeas%20have%20long%20been%20grown%20in%20the%20Southern,do%20not%20do%20well%20in%20very%20wet%20conditions

17. Cover Crop/Forage Tech Sheet. 2018. Iron Clay Cowpeas Summer. Annual Cover Crop. King’s AgriSeeds.

https://www.kingsagriseeds.com/wp-content/uploads/2018/02/Iron-and-Clay-Cowpeas.pdf

• Smith, M. and Gamble, A. 2023. Cover crops for Alabama. 2023 Alabama Cooperative Extension System, ANR 2139. https://www.aces.edu/blog/topics/row-cover-crop-soils/cover-crops-for-alabama/

19. Sheahan, C.M. 2012. Plant guide for cowpea (Vigna unguiculata). USDA-Natural Resources Conservation Service, Cape May Plant Materials Center, Cape May, NJ. Published 06/2012.

https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_viun.pdf

20. Myers, R. 2018. Growing Millets for Grain, Forage or Cover Crop Use. Division of Plant Sciences. Extension University of Missouri. https://extension.missouri.edu/publications/g4164 Assessed September 15, 2023.
21. Managing cover crops Profitably. 2012. Handbook Series Book 9. Published by the Sustainable Agriculture Research and Education (SARE) program, with funding from the National Institute of Food and Agriculture, U.S. Department of Agriculture. Third Edition.
22. Sheahan, C.M. 2014. Plant guide for pearl millet (Pennisetum glaucum). USDA-Natural Resources Conservation Service, Cape May Plant Materials Center, Cape May, NJ. Published 08/2014.

https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_pegl2.pdf#:~:text=Nevertheless%2C%20Rosolem%20et%20al.%20%282004%29%20found%20that%20pearl,can%20be%20used%20as%20a%20good%20surface%20mulch 

On lines 142 – 147, we also provided information regarding selected soils to summer cover crops supported by references (listed above):

The sandy loam soil was designated to grow iron clay peas cover crop as this summer legume grows best on sandy soils and full sunlight [16, 18, 19]. Pearl millet was planted on a clay soil (Davidson clay: a clayey kaolinitic thermic (oxidic) Rhodic Paleudults with 25% sand, 31% silt, 44% clay). Clay soil was chosen to grow pearl millet as it can grow very well on many different soils including clay soils [ 21, 22].

2. Some details could be provided in the materials and methods, such as the latitude and longitude information of the experiment,

Lines: 113 -115, we added: A three-year experiment, 2015-2017 growing seasons, was initiated at the Nation-al Soil Dynamics Laboratory (NSDL), Auburn, Alabama USA, (latitude North: 32.6 and longitude West: -85.5), having a subtropic climate.

the seeding rate of the covered crops. the number of plants measured for chlorophyll content in each plot, and brief description of methods to determine chlorophyll.

On lines 121 – 127 we added following information:

Each experimental plot area was 465 sq. m (0.0465 ha.) and both cover crops were broadcast in each growing season to the entire plot area 5.9 kg of seed for iron clay pea and 3.2 kg of seed for pearl millet utilizing a chest spreader for all three seasons. Planting rates per hectare were 127 kg/ha for iron clay peas and 68 kg/ha for pearl millet. Then seeds were tilled in (incorporated) and packed in with a steel mesh (basket) roller to provide a level surface and good seed to soil contact. A total of 16 plots with dimensions of 6.1 m long by 1.8 m wide were comprised in the field experiment.

Also, on lines 166 -174 we added following information:

Three chlorophyll measurements were taken of the leaves in each plot. The first measurement close to the centerline of the plot (lengthwise) was done approximately 0.5 m from the plot edge, the second was obtained about 2.0 meters from the first one, and the third one was taken also 2.0 m from the second one (about 0.5 m from the end of the plot). The leaf selection was based on a representative sample chosen randomly in proximity of the plot centerline. Average value from three samples was reported for each plot. Termination rate measurements were taken at the same time going through the 16 plots completing 48 measurements. All 48 measurements required approximately one hour to complete.

2. Line184-186: For iron clay peas, the highest biomass in 2015 was attribute to rainfall. But the precipitation in 2017 was more than that in 2015, please further explain why? Similarly, for pearl millet, the biomass might not only be related to rainfall?

4. Double-check the data of rolling twice treatment in Table 5, 2016, the average termination rate in 0day was much lower than other treatments, but the analysis of variance showed no significant difference?

       Data were checked in Table 5. Termination data is correct. At cover crop maturity as a healthy plant, chlorophyll activity is not the same across the cover crop area. Plant with termination rate 10.6% to 19.4%  is considered to be a healthy plant but more mature than other plants.

Also the termination rate of rolling one treatment on 0DAR, 2017, which was twice higher than that under other treatments, but no difference?

Cover crop maturity is dependent solely on the weather conditions such as rainfall and temperature. In hot summer months rainfalls can provide a positive development of cover crops, but too much rainfall can be detrimental for plant development and inhibit growth, thus altering the date which the crop reaches the ideal maturity for mechanical termination, especially at the same period at each growing season. Also, high temperature with a lack of rainfall can negatively affect cover crop growth, and obviously different weather conditions for each growing season influenced different growing periods from planting to reaching full maturity of the cover crops. Therefore, the length of growing cover crops from planting to reaching full maturity for mechanical termination does not affect mechanical termination using rolling/crimping technology.

Check whether the letter next to 72.8 in Table 6 is an a or a b?

The letter (a) is correct as no difference was detected between rolling two times (72.8%) and three times (75.6) with lower case “a” for both rolling treatments. The mean comparisons are valid only within each column, and in this case we compared treatment means in the column called DAR 7.

5. Line256: Please further explain "vining nature of this cover crop".

       On lines 332 – 334 we added more explanation:

Iron clay peas has stems that are trailing or creeping along the ground forming an interlocking thick mat on the soil surface. When used in a mixture, stems climb and interlock on stalks of other species such as millets, sorghum, and corn and loop around different plants.

6. Line293 " 63.9 % " not " 69.3 % ". The correct number is 63.9%; corrected on line 370.
7. Soil properties have been mentioned many times in the discussion of soil water content and soil strength. For example, Line 489-491, please specify? Is there any other soil properties data to support the discussion?

On line 579-582 we rephrased this statement, as we referred to the soil moisture content for which soil strength is dependent on. The values of soil strength were low as soil moisture was high.  

8. The best management measure for warm season cover crops should be put forward in the conclusions.

On lines 608 – 618 we added following paragraph in conclusions:

Based on results from this experiment, summer cover crops termination rates vastly increased with rolling/crimping twice or three times over the same cover crop area compared with a single pass. Such findings are important for organic systems with cover crops, where only mechanical termination such rolling/crimping can be utilized, as terminating cover crops with commercial herbicides is prohibited. Another important benefit from flattening and crimping cover crop against soil surface is conserving soil water through mulching barrier which resulted in higher volumetric soil moisture due to decreased water evaporation from soil. Notably, rolling/crimping twice or three times over the same cover crop area, did not cause soil compaction. Changes in soil strength was not affected by rolling treatments but was depended on changes in soil moisture.

Round 2

Reviewer 1 Report

For me the paper is fine. No issue was detected.

Reviewer 2 Report

The revised manuscript has undergone substantial revisions, and there are currently no additional comments.