Yield and Agronomic Performance of Sweet Corn in Response to Inoculation with Azospirillum sp. under Arid Land Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Please write the full name of B/C at the first time of writing

2. Keywords should be ordered alphabetically

3. Please briefly the introduction in paragraphs 5-7 into 1 paragraph. It no need to describe the details of the results of other experiments in the introduction.

4. How many crops did you do? Why did you do only 1 crop?

5. Please describe the plant growth-promoting activity of Azospirillum that you used in this study. Did you test the plant growth-promoting activity of Azospirillum that you used in your experiment?

6. Please show the figure of the experimental field.

7. Why did you not measure the soil fertility after the experiment?

8. Please discuss in deep why the Azospirillum stain you use in this study stimulates the growth and yield of corn.

9. How many days did you plant the corn?

10. Please check plagiarism by yourself and report the result of it to the editor.

Author Response

1. Please write the full name of B/C at the first time of writing.

We agree with this point. The full word Benefit/Cost ratio (BCR) was redacted.

2. Keywords should be ordered alphabetically

The words were arranged in alphabetical order in the Keywords.

3. Please briefly the introduction in paragraphs 5-7 into 1 paragraph. It no need to describe the details of the results of other experiments in the introduction.

We agree with this point. Paragraphs 5-7 were corrected and summarized in a single paragraph in the text.  Added some background information on Azospirillum in Peru.

4. How many crops did you do? Why did you do only 1 crop?

The research was conducted in a single location and planting season because this native strain of Azospirillum sp. had been previously evaluated in two other field experiments on yellow dent corn under surface irrigation (see references: Teodoro et al. 2020; Contreras-Liza et al. 2020). The objective of the present research was to determine the effect of the same Azospirillum strain on another maize race (the "Pardo" variety is a starchy white maize biotype with sweet endosperm) and under arid soil conditions with drip irrigation.

5. Please describe the plant growth-prooting activity of Azospirillum that you used in this study. Did you test the plant growth-promoting activity of Azospirillum that you used in your experiment?

The description and biochemical profile of the strain Azospirillum sp. has been improved in the corresponding section of the Methodology. Research is under development to determine the characteristics of the PGPR activity and genetic analysis of the native strain Azospirillum sp. under laboratory conditions, given that the growth-promoting activity has already been examined under field conditions in yellow dent crop, and now in sweet corn.

6. Please show the figure of the experimental field.

Attached is the experimental sketch

				4 m.					1 m.
.	To			T3			T2			T4
	T1			T0			T1			T2
	T2			T4			To			T3
	T3			T2			T4			To
	T4			T1			T3			T1

Block1 Block2 Block3 Block4

• Inoculation treatments :

T0, control without inoculation + 180 kg N per ha.

T1, one application of Azospirillum + 180 kg N per ha

T2, two applications of Azospirillum +180 kg N per ha

T3, one application of Azospirillum + 90 kg N per ha.

T4, two applications of Azospirillum + 90 kg N per ha.

7. Why did you not measure the soil fertility after the experiment?

The soil on which the research was conducted was sandy and arid. After the experiment, no substantial change in soil fertility was expected, due to the absence of organic matter and clay, as shown in the attached analysis. In any case, it is an interesting topic to be explored in another research, i.e. the impact of the inoculation of Azospirillum in the corn crop on the soil fertility level.

pH	E.C.	CaCO3	M.O.	P	K	Mechanical Analysis			Class	CEC	Exchangeable Cations					Sum	Sum	%
						Sand	Silt	Clay	Texture		Ca	Mg	K+	Na+	Al	of	of	Sat. from
	dS/m	%	%	ppm	ppm	%	%	%		meq/100g						Cations	Bases	Bases
8,11	6,46	3,00	0,36	40,6	403	90	4	6	Sandy	6,40	3,82	0,98	0,83	0,77	0,00	6,40	6,40	100

 

8. Please discuss in deep why the Azospirillum strain you use in this study stimulates the growth and yield of corn.

The possible mechanisms by which Azospirillum stimulates growth and yield in corn and other cereals have been added to the Discussion section.

Inoculation treatments with Azospirillum sp. were significant in the case of plant survival at harvest; concerning this finding Bashan & Levanony (1990) indicated that the most important effects of inoculation with this microorganism refer to morphological changes in the root system of the plant, which may be in agreement with the results of the present investigation.

Mechanisms by which bacteria can promote plant growth include the mobilization of nutrients and the production of phytohormones (Emgaberdieva, 2011). In the hypothesis put forward in the research, Azospirillum may have contributed to atmospheric nitrogen fixation in maize (Ferreira et al. 2020) and thus to the acquisition of this key element for plant growth (Fukami et al. 2018). Also, it has been proposed (Emgaberdieva, 2011) that free-living rhizobacteria such as Azospirillum have a clearer plant growth-promoting effect in soils with aridity or salinity problems. 

9. How many days did you plant the corn?

120 days from planting. This information has been added to the Methodology section.

The maize crop had a vegetative period of 120 days from planting, during this time all variable evaluations were carried out until harvest. Fertilization was carried out locally with nitrogen, phosphorus and potassium at 15 and 45 days after planting. For nitrogen fertilization, the application of the doses of the treatments in the experimental units was taken into account. 30 and 45 days after planting, manual weed control was practiced and some products such as chlorpyrifos and diazinon were applied for pest control. No fungicides were applied to avoid possible interactions with the inoculants; harvesting took place 120 days after sowing.

10. Please check plagiarism by yourself and report the result of it to the editor.

A similarity check was performed using Turnitn.

Thank you very much for your support to improve the manuscript.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

ijpb-3031610-peer-review-v1

Review

It is a very interesting topic and the results are promising. My main notes are: 

1) Tables 2 and 3 may not be needed in the manuscript. 

2) If needed, table 2 should be moved to the results section 

3) Description of variables in Methods should  be clear, for example "harvest date, days" is not clear for me. It also should be consistent with tables in Results (number of spikes vs flower number). What do the authors mean by flower number -values 25-35? 

4) Cost benefit ratio is a good plus, but there is no description on how gross value and production cost were calculated. 

5) References, either not cited in the text, or not listed 

Line 

52 Correa et al 2007 not listed

82 29% 82% is confusing. From 29 to 82%? 

125 Period at the end of sentence

126 seeds of sweet corn variety. "Pardo", was  ==> seed of sweet corn variety "Pardo" was...

137 Not clear what the authors want to say. 

148 Table 2. ANOVA for yield parameters. Should not be this table presented in the results section? 

151 Replace that were submitted for evaluation were ==> that were recorded

152 Grain wt per plot or per plant? See line 183

152 weight of grain==> grain weight

158 Analysis of data ==> Data analysis

159-162 English sounds too literal from Spanish, needs editing

172 presented ==> found 

176 Not sure if tables 2 and 3 should be included

180-181 Cob diameter is the same as ear diameter?  The negative effect was due to 50% N not due to inoculation

182 Ear length, was larger with 100 N and inoculation 

183 Grain weigth per plant or per plot? as in line  

198  Several doubt with the table.  Is plant survival shown as percentage or ratio? What do harvest date and flower number mean? Flower number per plot, per plant?   Seed wt per plant? Need additional explanation in Methods and units need to make sense. 

200-204 The description is based on absolute numbers, but control and 50% N + 2 inoc showed no statistic differences. 

210 The control treatment had the same yield as 50% N + inoc, NOT less 

206 Five annotations but only four in the table. 

257 Azospirillum is NOT a biofertilizer 

284 NOT cited in the text

329 NOT cited in the text

352 NOT cited in the text

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English needs editing, some sentences were literally translated from Spanish, and sound like that. Example: lines 159-152, and line 172.

Author Response

1) Tables 2 and 3 may not be needed in the manuscript. 

We agree with this point. Removed from the manuscript

2) If needed, table 2 should be moved to the results section 

Table 2 has been removed from the manuscript.

3) Description of variables in Methods should  be clear, for example "harvest date, days" is not clear for me. It also should be consistent with tables in Results (number of spikes vs flower number). What do the authors mean by flower number -values 25-35? 

The variables "days to harvest" and "number of flowers" have been agreed upon throughout the manuscript. In the latter case, it refers to the number of male flowers per experimental unit from sowing on a given date.

4) Cost-benefit ratio is a good plus, but there is no description of how gross value and production cost were calculated. 

We agree with this point. How the Cost-benefit ratio was calculated has been described and added to the Methodology.

5) References, either not cited in the text, or not listed 

Line 

52 Correa et al 2007 not listed

The reference Correa et al. 2007 was corrected by Caballero-Mellado 2001

82 29% 82% is confusing. From 29 to 82%? 

We agree with this point. Removed that part of the paragraph

125 Period at the end of sentence

Corrected

126 seeds of sweet corn variety. "Pardo", was  ==> seed of sweet corn variety "Pardo" was…

Corrected

137 Not clear what the authors want to say. 

Removed that part of the paragraph

148 Table 2. ANOVA for yield parameters. Should this table not be presented in the results section? 

We agree with this point. Table 2 was removed

151 Replace that were submitted for evaluation were ==> that were recorded

Corrected

152 Grain weight per plot or per plant? See line 183

Grain weight per plot 

152 weight of grain==> grain weight

Corrected

158 Analysis of data ==> Data analysis

We agree with this point. Corrected

159-162 English sounds too literal from Spanish, needs editing

We agree with this point. The English translation has been further revised to improve the manuscript.

172 presented ==> found 

Corrected.

176 Not sure if tables 2 and 3 should be included

Tables 1 and 2 have been removed from the manuscript.

180-181 Cob diameter is the same as ear diameter?  The negative effect was due to 50% N not due to inoculation

The correct word is "ear diameter", the error has been corrected.

182 Ear length, was larger with 100 N and inoculation 

We agree with this point, corrected in the manuscript

183 Grain weight per plant or per plot? as in line  

Grain weight per plot is the right.

198  Several doubt with the table.  Is plant survival shown as percentage or ratio? What do harvest date and flower number mean? Flower number per plot, per plant?   Seed wt per plant? Need additional explanation in Methods and units need to make sense. 

We agree with these points.

Plant survival to harvest is shown as a percentage (%).

The term "days to harvest" has been corrected in the manuscript.

Corrected the term "number of flowers per plot" in the Table.

The variable is the "weight of 100 seeds" for each treatment in the Table.

200-204 The description is based on absolute numbers, but control and 50% N + 2 inoc showed no statistical differences. 

We agree with this point, there are no statistical differences.

210 The control treatment had the same yield as 50% N + inoc, NOT less 

We agree with this point. Corrected.

206 Five annotations but only four in the table. 

We agree with this point. Corrected in the table.

257 Azospirillum is NOT a biofertilizer 

The word biofertilizer was removed and corrected to bacterial strain.

284 NOT cited in the text

Removed from references

329 NOT cited in the text

Removed from references

352 NOT cited in the text

Removed from references

Comments on the Quality of English Language

English needs editing, some sentences were literally translated from Spanish, and sound like that. Example: lines 159-152, and line 172.

We agree with this point. The English translation has been further revised to improve the manuscript.

Thank you very much for your support to improve the manuscript.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

There are three questions that I could not find in your manuscript

1. How many crops did you do? Why did you do only 1 crop?

2. Please show the figure of the experimental field.

3. Why did you not measure the soil fertility after the experiment?

None

Author Response

1. How many crops did you do? Why did you do only 1 crop?

The research was conducted in a single location and planting season because this part of the evaluation of a native strain of Azospirillum sp. had been previously evaluated in two other field experiments on yellow dent corn (see references: Teodoro et al. 2020; Contreras-Liza et al. 2020). The objective of the present research was to determine the effect of the same Azospirillum strain on another maize race (the cv. "Pardo" is a starchy white maize biotype with sweet endosperm) and under arid soil conditions. Currently, research is being conducted with the same bacterial strain in another native race of starchy corn called "purple corn" to have complete field data on the growth-promoting activity of the native Azospirillum strain.

2. Please show the figure of the experimental field: Attached is the experimental sketch in pdf.
3. Why did you not measure the soil fertility after the experiment? 

   The soil on which the research was conducted was sandy and arid. After the experiment, no substantial change in soil fertility was expected, due to the absence of organic matter and clay, as shown in the attached analysis. In any case, it is an interesting topic to explore in another research, i.e., the impact of the inoculation of Azospirillum in the corn crop on soil fertility.

    

   Attached the soil analysis. 
   
   

   pH	EC	CaCO3	OM	P	K	Mechanical Analysis			Class	CEC	Exchangeable Cations					Sum	Sum	%
   						Sand	Silt	Clay	Texture		Ca	Mg	K+	Na+	Al	of	of
   	dS/m	%	%	ppm	ppm	%	%	%		meq/100g						Cations	Bases	Bases Sat.
   8.11	6.46	3.00	0.36	40.6	403	90	4	6	Sandy	6.40	3.82	0.98	0.83	0.77	0.0	6.40	6.40	100

    

Author Response File: Author Response.pdf

Reviewer 2 Report

Move table 2 to results section 

Double check values of grain wt per plot (g) in table 2 and 100-seed wt (kg). In both cases values does not make sense. 

1) Table 2. Math between yield kg ha-1 and grain wt per plot does not match 

Plot size is described as 4 rows, 4 m long and 0.9 m apart, that makes 14.4 m2. Therefore, considering the numbers in Table 2, either the plot varies in size (from 1.4 to 1.9 m2) or the yield is much lower (694 plots per hectare, giving 350-400 kg per hectare)

Number of "plots" required per hectare would vary from 5139 to 6920 to

Control (100%N): 2968.32 / 0.5775 = 5139.9 "plots"

100%N+A1+A2: 3434.23 / 0.49625 = 6920.4 "plots"

2) Table 3. 100-seed weight does not makes sense. On my experience one maize seed weighs between .2 and .5 g, and given the values each seed should weigh more than 9 g. In the previous version this variable was reported "seed wt" without further reference. 

Comments for author File: Comments.pdf

Author Response

1) Table 2. Math between yield kg ha-1 and grain wt per plot does not match 

Plot size is described as 4 rows, 4 m long and 0.9 m apart, that makes 14.4 m2. Therefore, considering the numbers in Table 2, either the plot varies in size (from 1.4 to 1.9 m2) or the yield is much lower (694 plots per hectare, giving 350-400 kg per hectare).

Thank you for your question because the Methodology omitted how the total corn yield per hectare was estimated. The estimation of yield per hectare was made taking into account not only the grain weight per experimental unit but also the weight of the ear (grain + cob) in the sample of the two central furrows of the experimental unit.

The yield per hectare was projected as follows:

Yield kg ha^-1 = (Weight of ears plot^-1 ) x (sample area of the two central rows of the experimental plot) x (plant density adjustment, % plants surviving to harvest).

Adjustment for plant population density was used because inoculation treatments significantly influenced plant survival at harvest as shown in Table 3.

It should be noted that the total weight of the ears (grain and cob) was used as an indicator of yield per hectare because the "Pardo" variety and other starchy maize varieties are sold not in grain, but with the complete ear.

The Methodology section will describe the total yield estimation per hectare since it was not included in this section. In addition, the name of the variable "Grain Yield" has been corrected to "Total Yield" in Table 4.

2) Table 3. 100-seed weight does not makes sense. On my experience one maize seed weighs between .2 and .5 g, and given the values each seed should weigh more than 9 g. In the previous version this variable was reported "seed wt" without further reference.

We agree with this point. 

There was an error in the denomination of the variable since it should have been "Weight of 1000 seeds" instead of "Weight of 100 seeds". Consider in this case that the white maize "Pardo" seed is considerably larger than the yellow dent corn seeds with an average weight of 0.90 kg per 1000 seeds. I am enclosing a brochure on the variety INIA 620 "maíz choclero"  similar to cv. "Pardo", although it is in Spanish, for which I apologize. In Table 3 "Weight of 100 seeds" has been changed to "Weight of 1000 seeds".

 

Author Response File: Author Response.pdf