Supplementing Nitrogen in Combination with Rhizobium Inoculation and Soil Mulch in Peanut (Arachis hypogaea L.) Production System: Part II. Effect on Phenology, Growth, Yield Attributes, Pod Quality, Profitability and Nitrogen Use Efficiency

Reviewer’s comment        

Authors’ response

1. In the Fig.7 and 8, I can't understand why you chose the formulas.

If you want to check the relationship between NUE and ND, I think dot of ND=1 should be removed and fit to approximate line or curves.

We thank the reviewer for this helpful comment. We have amended Figures 7 & 8 and their captions to improve clarity and meaning. Changes now at lines 552-563.

2. If you publish part 3, I would like you to analyze the environmental impact, because the problems of nitrogen dose are not only economic but environmental.

We are grateful to the reviewer for this prescient suggestion: the environmental impacts of N fertilizer and mulching have recently been published:

M. Mondal, S. Garai, H. Banerjee, S. Sarkar, R. Kundu, Mulching and nitrogen management in peanut cultivation: an evaluation of productivity, energy trade-off, carbon footprint and profitability, Energy, Ecol. Environ. (2020). https://doi.org/10.1007/s40974-020-00189-9.

Reviewer’s comment

Authors’ response

1. This article describes the productivity and profitability of irrigated peanut as influenced by mulch and nitrogen fertilization as a complement of seed inoculation. The amount of data provided in this article is great. However, data are not well presented and analyzed. The abstract lack of a sentence explaining the reason why the Authors do this experiment, and the objectives. In the same way, the introduction has not a sentence where the objective is clearly stated and needs to provide more background information about mulch in peanuts in another part of the world, and nitrogen fertilization in legumes.

We thank the reviewer for this constructive suggestion. We have added to the abstract and introduction to better clarify the aims and objectives of this research: these additions are now at lines 29-33, 65-70 and 92-101.

The two majors’ issues are the use of plant populations in calculations for expressing the measurements of individual plants on an area basis and the statistical analysis that seems to not be appropriate for a split-plot design. The authors do not explain in the methods how do they account for the plant population. Indeed, it is never reported, and it seems that the authors assume the same plant population in every plot because they pick randomly plants instead of sampling one meter of the row for example. While picking random plants is not wrong it has the issue of the space between plants on the same row that is needed for calculating the area. Regarding the statistical analysis for a split-plot, it should show the whole plot error, subplot error, and total error.

We have amended the material and methods to better explain the research methodology used at lines 121, 137-138 and 201-205.

Finally, the section of results and discussion is too long and descriptive rather than a discussion. The authors can separate it into two sections or shorten the current section.

Respectfully, we consider that a combined results & discussion is shorter than two separate sections. Our preference is to maintain the current length as we believe we present much interesting and novel research, however if the editor requests we are happy to edit this section to reduce its length.

2. #57: a comma is missing after “…mulches…”

The correction has been done. Please check now line no. 61

3. #80: Do the 41 kg N ha^-1 take into account the N removal from seeds when peanut is harvested? A clarification may be needed.

This is the finding of an earlier study reported by Argaw (2017), who reported that legume rhizobium symbiosis added 41 kg N ha^-1annually into soil under peanut cultivation. The amount of N added may vary with microorganism activity, geological locations of the crop, peanut species and also environment. We have added some additional examples to clarify our statement: at lines 90-95

4. #100: What is the RND amount? The authors must report the kg of N added in each treatment

RND means recommended nitrogen dose; this acronym is explained on line 114. We have clarified the amount (ie kg ha^-1) of N added in each treatment at line 113

5.  #103: same comment for P and K

Thank you so much, we have also explained the dosages (in kg ha^-1) of P and K applied in the experiment; these are shown at line 117

6. #105: 150 kg ha^-1 is ok but what is the plant population? And row spacing?

Plant populations (33 m^-2) and row spacing (30 cm) are mentioned at lines 120-121

7. #108: “…as per crop need” is a very vague phrase. What was the methodology to calculate the crop needs?

We have provided additionaldetails regarding irrigation requirement, now at lines122-125.

8. #118-120: The authors must describe how they come up with the yield per area by picking five random plants.

We have added a description of how we calculated yield per plot area from five plants picked at random; this is now at lines137-138.

9. #183: A minimum detail of the statistical analysis must be provided. Only the specifications can be directed to a previous article.

We have provided a more detailed summary of the statistical analyses conducted in this research; now at lines 201-205.

10. Figure #1: add letters showing the significant differences between treatments.

Respectfully, we think that adding letters onto these figures to show significant differences will add confusion as they are likely to overlap each other and be difficult to read. Instead, we prefer to use the error bars displayed on the figures which also indicate the variability between treatments. We have not altered Figure 1 in response to this comment

11. Figure #2: adding titles to the panels will help to go through the data easily. Also, add letters with significant differences between treatments.

As with Figure 1, we prefer to demonstrate variability through error bars rather than letters to show significant difference. We have not altered Figure 2 in response to this comment.

12. Figure #3: Panel c and d are missing the “n” in dry matter accumulation. The authors may want to specify whether it is whole plant dry matter (including roots) or aboveground dry matter.

We have clarified the spelling on the Y-axis captions for Figure 3. The figure caption specifies that the dry matter is aboveground dry matter.

13. Figure #7 and 8: The quadratic equation adjusted to the data is not correct and has nothing to do with the data pattern. Better to not show any equation. Doses should be expressed as kg of N ha^-1. The second dose point is missing in Figure #7.

We have changed the equations for Figures 7 & 8 and have added the second dose for Figure 7

Reviewer’s comment

Authors’ response

1. You have looked at the number of nodules. Have you thought about pursing the nitrogen fixing activity of these nodules?

We thank the reviewer for this suggestion. Examining the nitrogen-fixing activity of nodules was outside the scope of this research.

2. Some of the sections of this article like experimental details, statistical analyses are referred to part 1, unfortunately reviewer cannot go through them since part 1 is not published yet. Can you add some details?

We appreciate the challenge of reviewing a MS which references another MS, however our concern in publishing both together was to reduce duplication. We have added some additional details, particularly in the materials and methods (lines 102-205) to provide additional background for those who reading this manuscript alone.

3. Figure 1 and 2- can you add year 2015-16 and 2016-17 to each of the graph? I think it helps readers to follow easily

We have added the 2015-16 and 2016-17 season information to Figures 1 and 2.

4.Overall, 100% RDN + Rh treatment had advantage in terms of yield, revenue and cost-benefit ratio but you also mentioned about adverse effect of root nodulation and fertilizer N use efficiency. Long term perspective, how sustainable this treatment would be? Do you think, a balanced treatment like 75% RDN or other would be an optimal in terms of environment, soil health?

In the present experiment we recommend the dose 100% RDN + Rhizobium inoculum to achieve better yield and economic viability, but in the longer term we should also estimate the energy requirements and environmental effects of these different management practices. These are potential future research investigations.

Another paper from this research entitled: ‘Mulching and nitrogen management in peanut cultivation: an evaluation of productivity, energy trade-off, carbon footprint and profitability’ has been published in a Springer Journal (Energy, Ecol. Environ.) and addresses some of these questions.

M. Mondal, S. Garai, H. Banerjee, S. Sarkar, R. Kundu, Mulching and nitrogen management in peanut cultivation: an evaluation of productivity, energy trade-off, carbon footprint and profitability. Energy, Ecol. Environ. (2020). https://doi.org/10.1007/s40974-020-00189-9

Reviewer 2 (Second round) comments

Authors response

1. The authors have two years of experiment, but they run one ANOVA per year. In the case of a combined ANOVA, the year is usually treated as a random factor. I do not see that the authors run a combined ANOVA. While it is not bad to run two separate ANOVA (one per each year), it is not called combined ANOVA and each ANOVA (per year) must follow the appropriate analysis for a split-plot design that shows the whole plot error, subplot error, and total error.

Many thanks for the suggestions. Yes… we did not perform the pooled analysis. We presented the year wise analysis using the appropriate ANOVA for split plot analysis (The significant levels for N, Mulching [subplot and main plot] and N × Mulching [interactions] were given in the Tables). Moreover, we have provided the different error values of the ANOVA in supplementary Table1S (Please also check it below next page). 

The combined analysis is not a best chose for all type of experiment as pooling of the data considering the year a factor, often the effect of year (mainly due to uncontrolled factors like rainfall, temperature etc.) may not be properly assessed on subplot and main plot factors. Moreover, we performed the Butlett- Chi Square test to judge the homogeneity of our data set between tow years and found that combined analysis did not increase the efficacy of the ANOVA and increasing the residual errors. Realizing these issues, we performed the year wise analysis to assess the year-over impact of N and Rhizobium on soil, crop dynamics of pea nut production system grown with or without mulching condition.   

2. Regarding the error bars vs significance differences, they are not the same. The authors can easily do a better use of the figure space by reducing the space between a group of bars and including the legend in the plot. Doing that, a letter explaining significant differences can easily be seen and the figure self-explained. 

2. Figures has been corrected as suggested

3. Finally, the equation in figure Figure 7 and 8 is just fine, but the x-axis should be in kg ha-1 rather than doses. That way the equation parameters will have a biological meaning.

3. Figures has been corrected as suggested

Variables

Whole plot (SC)

Sub-plot (N)

SC×N

Total

2015-16

2016-17

2015-16

2016-17

2015-16

2016-17

2015-16

2016-17

Er (SS)

Er (MS)

Er (SS)

Er (MS)

Er (SS)

Er (MS)

Er (SS)

Er (MS)

Er (SS)

Er (MS)

Er (SS)

Er (MS)

Er (SS)

Er (MS)

Er (SS)

Er (MS)

Seedling emergence (%)

535.71

535.71

360.21

360.21

104.57

17.43

110.57

18.43

16.29

2.71

22.29

3.71

822.57

-

659.07

-

Leaf area index

45 DAE

0.90

0.90

0.79

0.79

1.55

0.26

1.37

0.23

0.09

0.01

0.03

0.005

2.57

-

2.21

-

60 DAE

3.04

3.04

2.89

2.89

5.64

0.94

7.70

1.28

1.19

0.20

0.32

0.05

121.88

-

127.58

-

Nodule number plant^-1

45 DAE

55.54

55.54

35.11

35.11

365.63

60.94

1515.12

252.52

60.81

10.13

66.06

11.01

1150.33

-

1893.30

-

60 DAE

269.59

269.59

310.54

310.54

3007.78

501.30

4387.58

731.26

40.78

6.80

211.74

35.29

18409.21

-

6374.92

-

Pod dry wt. (g plant-¹)

293.52

293.52

836.25

836.25

1644.48

274.08

1008.63

168.10

42.66

7.11

98.99

16.50

2044.47

-

1985.39

-

Peg to pod conversion (%)

1670.01

1670.01

410.97

410.97

4729.21

788.20

2444.79

407.46

384.73

64.12

118.63

19.77

7473.80

-

3562.45

-

Shelling (%)

68.28

68.28

44.19

44.19

128.45

21.41

221.67

36.95

11.48

1.91

2.91

0.48

265.74

-

313.59

-

N uptake

Kernel

3769.89

3769.89

4071.58

4071.58

16483.51

2747.25

19049.17

3174.86

319.16

53.19

334.13

55.69

21032.75

-

24012.89

-

Haulm

1532.45

1532.45

642.56

642.56

8075.82

1345.97

10915.35

1819.22

133.78

22.30

77.94

12.99

9879.21

-

12831.42

-

P uptake

Kernel

137.08

137.08

96.25

96.25

857

142.83

1086.12

181.02

22.34

3.72

16.84

2.80

1034.81

-

1226.93

-

Haulm

50.45

50.45

3.33

3.33

119.86

19.98

74.09

12.35

48.49

8.08

0.81

0.13

475.41

-

86.34

-

K uptake

Kernel

132.82

132.82

102.50

102.50

529.83

88.30

646.90

107.81

13.17

2.19

10.78

1.80

691.77

-

778.31

-

Haulm

772.59

772.79

344.98

344.98

4063.18

677.20

5502.14

917.02

74.37

12.40

30.13

5.02

5024.02

-

6587.81

-

Oil %

0.05

0.05

0.21

0.21

392.37

65.39

435.26

72.54

0.12

0.02

0.15

0.03

419.73

-

456.67

-

Protein %

0.02

0.02

0.05

0.05

112.36

18.73

88.37

14.73

0.13

0.02

0.06

0.01

170.18

-

95.34

-