Maize productivity and soil nutrients variations by the application of vermicompost and biochar.

Poor soil organic matter is one of the major causes of the deterioration of soil health. Most soils fertility is also decreased when enough organic carbon is not present in the soil. Maize is most susceptible to this poor soil fertility status. A significant amount of maize growth and yield is lost when it is cultivated in low organic matter and poor fertility soil. To overcome this issue organic amendments can play an imperative role. Biochar and vermicompost are organic amendments that can not only improve organic residues but also increase soil nutrient concentration. The current experiment was conducted to explore the sole and combined application of both organic amendments with recommended NPK fertilizer. Four treatments were tested i.e., control, biochar (BC1), vermicompost (VC1) and VC1+BC1 with and without nitrogen (N), phosphorus (P) and potassium (K) in the experiment. Results showed that VC1+BC1+NPK performed significantly best for improvement in maize plant height (6.25 and 3.00%), 1000 grains weight (30.48 and 29.40%), biological yield (18.86 and 43.12%) and grains yield (30.58 and 39.59%) compared to BC0+VC0+NPK and control respectively. A significant improvement in soil N, P and K also validated the efficacious role of VC1+BC1+NPK over BC0+VC0+NPK and control. Treatment VC1+BC1+NPK is recommended for the achievement of better maize growth and yield in poor organic matter soils. More investigations are suggested in variable climatic conditions to declare VC1+BC1+NPK as the best amendment compared to control for enhancing soil N, P and K status as well as maize productivity.

Introduction

Maize (Zea mays L.; family Poaceae) is a Kharif, cross-pollinated and short-day crop cultivated in Pakistan. It is a multipurpose cereal crop used as food, feed and raw material for humans, animals and industries respectively [1]. Both irrigated, as well as rain-fed areas, are suitable for its cultivation. Sandy loam to clay loam are desired soil textures that support maize productivity compared to other textures [2]. Maize is a major cereal grain crop after rice and wheat. In Pakistan maize is 4th largest crop cultivated after wheat, rice and cotton. Maize grain is nutritionally important because it includes the source of vitamins, proteins, starch and minerals. One hundred grams (100g) of fresh maize contain 361 calories of energy, 9.4 grams of protein, 4.3 grams of fats, 74.4 g carbohydrates, 1.8 grams fibre, 1.3 grams of ash and vitamins in milligram [3]. However, poor soil organic matter and soil fertility status adversely affect the growth and productivity of maize [4-7].

To overcome this issue addition of organic amendments are usually suggested [8-11]. Biochar (BC) is one such solid porous material. It is obtained from the thermochemical transformation of plant biomass at high temperatures (350–600˚C) in a low O2 supply [12]. The quality which makes biochar more attractive as a soil amendment is being porous structure [13]. On the other hand, BC is enriched with hydrogen (H), nitrogen (N), oxygen (O), phosphorus (P), potassium (K) and carbon (C) [5]. That’s why the application of biochar can also boost soil fertility and minimize carbon emission [14]. Biochar application improves soil properties like increased water holding capacity (WHC), increase CEC, higher pH, reduce nutrients leaching and providing nutrients to the soil by itself [12], hence safeguards crops against water stress [8,15-17].

Vermicompost (VC) is another popular organic amendment. It is the product of the decomposition of various worms species i.e., red wigglers, earthworms and white worms to develop a mixture of decomposing food waste and vegetables, vermicast and bedding materials [18]. These castings contain minimum levels of pollutants with saturation of nutrients over organic materials prior to vermicomposting [18]. Vermicompost have water soluble nutrients. It is an excellent, nutrient enrich soil organic conditioner and fertilizer. Mostly large and small scale farming use it as sustainable, organic matter [19]. Earthworms indirectly promote microbial activity and biomass via aeration and fragmentation by increasing the available surface area for microbes. Thus affecting the structure and composition of the microbial communities [20].

Therefore, keeping in mind, the potential benefits of VC and BC, the current study was conducted on maize. This study is covering the knowledge gap of VC and BC utilization as a sole amendment and in combination with recommended NPK fertilizers. The aim of the study was improvement of selection of best VC and BC combination with and without NPK for enhancement in maize growth and yield. It is hypothesized that combined application of VC and BC with NPK might be an effective amendment than sole application for improvement in maize productivity in low organic matter and poor fertility soils.

Material and methods

Experimental site and design

Field trial was done in the Peshawar research farm (34.1°’21” N, 71°28’5’E), University of Agriculture, during summer 2020 with experimental layout randomized complete block design (RCBD).

Plot size and plant spacing

The plot size was kept 5×5 m2 with plant-plant distance 25–30 cm while row-row was 75 cm. Maize hybrid pioneer 3025w variety were used in the experiment. Standard protocols were used for the analysis of pre-experimental soil (Table 1).

Table 1

Pre-experimental soil characteristics.

Characteristics	Unit	Value	References
Sand	%	30.3	[21]
Silt	%	64.2
Clay	%	5.5
Textural class	-	Silt loam
pH (1:5)	-	7.53	[22]
EC (1:5)	dSm-1	0.17	[23]
Organic matter	%	0.71	[24]
Total N	%	0.036	[25]
Available P	mg kg−1	2.4	[26]
Extractable K	mg kg−1	143	[27]

Maize variety and fertilizer application

Basal dose of nitrogen (N), phosphorus (P) and potassium (K) was soiled @ 120-90-60 kg ha-1 from urea, single superphosphate and sulphate of potash [28]. A full dose of P, K and ½ N were soiled just before sowing and incorporated/mixed and another ½ N was soiled after 35 days of the emergence of the crop with irrigation water.

Biochar

Biochar was produced by pyrolysis of locally available mixed wood chips (hardwood) in a muffle furnace (450 ˚C for 4 h) and was grinded before applying to the field [29]. Biochar produced had total C, N and P content of 67.3%, 1.03% and 0.21% respectively with C:N = 65.34 and pH = 8.2.

Vermicompost

Crop residue and garden waste was used to prepare vermicompost. On partial composting, Eisenia fetida were introduced and the vermicompost (with pH 6.2, total C 23.2%, total N 1.30%, C:N 12.21, total P 0.89%, mg kg-1, bulk density 1.12 Mg m-3 and water holding capacity of 55.18%) was ready after 90 days.

Treatment plant

Total four combinations of VC and BC were applied with and without NPK in three replicates. The treatments include control (No BC (BC0)+No VC(VC0)), BC1 (10 t ha-1 biochar), VC1 (10 t ha-1 vermicompost) and BC1+VC1 (5+5 t ha-1 biochar and vermicompost), BC0+VC0+NPK, BC1+NPK, VC1+NPK and VC1+BC1+NPK. Treatments included BC and VC were applied manually as per the treatment plan.

Irrigation

During the maize growing season, six irrigation events were applied, with each event being equivalent to 75 mm, except the first (pre-planting) which was equivalent to 100 mm.

Harvesting and data collection

At crop maturity plants were harvested. The measuring tape was used for plant height determination. A thousand grains were counted manually from treatment after threshing and weighed using analytical grade balance.

Biological and grains yield

The biological yield was recorded by suing the formula of

For the grain yield, two central rows in each treatment were harvested.

Soil pH and EC

Deionized water and soil were mixed in 5:1 ratio. After 15 min shaking pH was analyzed using pH meter [22]. Water and soil samples were taken at a ratio of 5:1 means 50 ml of water and 10 g of soil sample. Then the mixture was put on the mechanical shaker for 15min for shaking. After that EC was found with the help of a conductivity meter [23].

Soil organic matter

Organic matter was determined by treating 1 g of soil with 10 ml of 0.5 N K2Cr2O7 and 20 ml of concentrated H2SO4. Final titration was done with ferrous ammonium sulphate solution [24].

Soil total nitrogen

Total nitrogen was determined in soil samples with the help of Kjeldhal’s method by Bremner and Mulvancy [30].

Soil phosphorus and potassium

Both nutrients were determined by the method prepared by Soltanpour and Schwab [31]. 10g soil sample was taken in a flask and 20ml of extractable ABDTPA solution were added to it. After shaking for 15min K contents were computed on a flame photometer. For P, one ml of solution was taken in a 25ml volumetric flask. Add 5ml of ascorbic acid reagent and make the solution up to 25ml with distilled water. These flasks were then placed in a dark place until it changes the colour and then find out the P content through a spectrophotometer.

Statistical analyses

The standard statistical procedure was adopted for the statistical analyses of data [32]. The paired comparison was applied using fertilizer and organic amendments as factors on Origin2021b [33]. Fisher LSD test was applied for comparison of each treatment at p ≤ 0.05. Pearson correlation and principal component analysis were also performed on Origin2021b.

Results

Plant height and 1000 grains weight

Results showed that the application of treatments significantly changed plant height and 1000 grains weight. Compared to control (BC0+VC0+No NPK), BC1 and VC1+BC1 significantly increased plant height. No significant change was noted in plant height between VC1 and control. The addition of VC1+BC1+NPK caused significant improvement in plant height over BC0+VC0+NPK (Fig 1A). Treatments BC1+NPK and VC1+NPK remained statistically alike to each other and with BC0+VC0+NPK for plant height. Maximum increase of 6.25 and 3.00% in plant height was observed in VC1+BC1+NPK and VC1+BC1 than BC0+VC0+NPK and control respectively. For 1000 grains weight, BC1, VC1 and VC1+BC1 caused significant enhancement compared to control. It was also noted that BC1+NPK, VC1+NPK and VC1+BC1+NPK also performed significantly better than BC0+VC0+NPK for improvement in 1000 grains weight. No significant change in 1000 grains weight was noted between VC1+NPK and VC1+BC1+NPK (Fig 1B). Maximum increase of 30.48 and 29.40% in 1000 grains weight was observed in VC1+BC1+NPK and VC1+BC1 than BC0+VC0+NPK and control respectively.

Fig 1

Effect of sole and combined application of vermicompost (VC1) and biochar (BC1) in the presence and absence of recommended NPK fertilizer on maize plant height (A) and 1000 grains weight (B). Different values on bars are showing significant change at p ≤ 0.05; Fisher LSD. NPK = Nitrogen, Phosphorus and Potassium.

The addition of treatments significantly affects biological and grains yield. Over control (BC0+VC0+No NPK), BC1, VC1 and VC1+BC1 significantly improved biological yield. Application of BC1+NPK, VC1+NPK and VC1+BC1+NPK also caused significant enhancement in biological yield over BC0+VC0+NPK (Fig 2A). Treatments BC1+NPK, VC1+NPK and VC1+BC1+NPK remained statistically similar to each other for biological yield. Maximum increase of 18.86 and 43.12% in biological yield was noted where VC1+BC1+NPK and VC1+BC1 were applied over BC0+VC0+NPK and control respectively. For grains yield, BC1, VC1 and VC1+BC1 caused a significant increase over control. Treatments BC1+NPK, VC1+NPK and VC1+BC1+NPK also differed significantly better compared to BC0+VC0+NPK for enhancement in grains yield. No significant change in grains yield was between BC1+NPK, VC1+NPK and VC1+BC1+NPK (Fig 2B). Maximum increase of 30.58 and 39.59% in grains yield was noted in VC1+BC1+NPK and VC1+BC1 than BC0+VC0+NPK and control respectively.

Fig 2

Effect of sole and combined application of vermicompost (VC1) and biochar (BC1) in the presence and absence of recommended NPK fertilizer on maize biological (A) and grains yield (B). Different values on bars are showing significant change at p ≤ 0.05; Fisher LSD. NPK = Nitrogen, Phosphorus and Potassium.

Soil pH and organic matter

It was noted that control (BC0+VC0+No NPK) and VC1+BC1 did not differ significantly for soil pH. Application of BC1 and VC1 caused a significant decrease in soil pH over control (Fig 3A). Treatments BC1+NPK, VC1+NPK remained statistically similar with BC0+VC0+NPK for soil pH. However, VC1+BC1+NPK significantly increased soil pH than BC0+VC0+NPK. In the case of organic matter, BC1, VC1 and VC1+BC1 caused significant improvement compared to control. Treatments BC1+NPK, VC1+NPK and VC1+BC1+NPK also remained significantly better than BC0+VC0+NPK for an increase in organic matter (Fig 2B). Maximum increase of 26.72 and 29.33% in soil organic matter was noted in VC1+BC1+NPK and VC1+BC1 compared to BC0+VC0+NPK and control respectively.

Fig 3

Effect of sole and combined application of vermicompost (VC1) and biochar (BC1) in the presence and absence of recommended NPK fertilizer on soil pH (A) and organic matter (B). Different values on bars are showing significant change at p ≤ 0.05; Fisher LSD. NPK = Nitrogen, Phosphorus and Potassium.

Soil nitrogen, phosphorus and potassium

Treatments BC1, VC1 and BC1+VC1 caused significant improvement in total soil N over control (Fig 4A). The addition of BC1+VC1 also differed significantly better for improvement in soil N compared to BC1 and VC1. Similarly, BC1+NPK, VC1+NPK and VC1+BC1+NPK caused a significant increase in soil N than BC0+VC0+NPK. Maximum increase of 35.82 and 41.89% in soil N was noted in VC1+BC1+NPK and VC1+BC1 than BC0+VC0+NPK and control respectively. For soil P, BC1 and VC1 did not bring any significant change over control. A significant improvement in soil P was noted where VC1+BC1 was applied over control (Fig 2B). Results also showed that BC1+NPK did not differ significantly over BC0+VC = +NPK for soil P. However, VC1+NPK and VC1+BC1+NPK remained significantly better for improvement in soil P compared to BC0+VC0+NPK. Maximum increase of 88.35 and 89.13% in soil P was observed in VC1+BC1+NPK and VC1+BC1 compared to BC0+VC0+NPK and control respectively. In the case of soil K, BC1, VC1 and VC1+BC1 caused a significant enhancement than control. Treatments BC1 and VC1 remained statistically similar to each other for soil K. However, BC0+VC0+NPK, BC1+NPK and VC1+NPK did not differ significantly from each other for soil K. Only application of VC1+BC1+NPK caused significant increase in soil K compared to BC0+VC0+NPK (Fig 4C). Maximum increase of 16.06 and 18.67% in soil K was observed in VC1+BC1+NPK and VC1+BC1 compared to BC0+VC0+NPK and control respectively.

Fig 4

Effect of sole and combined application of vermicompost (VC1) and biochar (BC1) in the presence and absence of recommended NPK fertilizer on soil N (A), soil P (B) and soil K (C). Different values on bars are showing significant change at p ≤ 0.05; Fisher LSD. NPK = Nitrogen, Phosphorus and Potassium.

Pearson correlation and Principal component analysis

Pearson correlation showed that soil pH was significantly positive in correlation with soil K and P. Organic matter also showed a significant positive correlation with soil N, P and K. Soil N was positive non-significant in correlation with soil pH. A significant positive correlation also existed between soil N, P and K with plant height, 1000 grains weight, biological and grains yield (Fig 5). According to principal component analysis variables explained 84.5% of the variation in the first two axes (Table 2; Fig 6), i.e., 17.6% and 66.9% variances were accounted for the first and second principal components, respectively. The 1st principal component (PC1) captured a higher number of attributes compared to 2nd (PC2). All the studied attributes were closely linked to VC1+BC1 except soil pH. Plant height was more responsive towards soil N, P and K. Biological yield, grain yield and 1000 grains weight were more responsive towards soil organic matter. Soil nutrients were more closely linked with NPK compared to control (Table 3; Fig 7).

Fig 5

Pearson correlation for studied maize and soil attributes.

Green color is indicating positive while blue color is indicating negative correlation. Ellipse having no stars are non-significant while having stars are significantly different in correlation.

Table 2

Eigenvalues, loadings, percentage of variance and cumulative of studied PCA attributes using organic amendments as group.

Principal Component	Eigenvalue	PC1	PC2	Percentage of Variance (%)	Cumulative (%)
		Loadings
Plant Height (cm)	6.02537	0.33159	0.24186	66.94852	66.94852
1000 Grains Weight (g)	1.58297	0.36776	-0.26377	17.58856	84.53708
Biological Yield (kg/ha)	0.47141	0.31081	-0.32268	5.23786	89.77494
Grain Yield (kg/ha)	0.36828	0.32512	-0.36128	4.09202	93.86696
Soil pH	0.26748	0.1462	0.66856	2.972	96.83896
Organic Matter (%)	0.13383	0.36064	-0.18326	1.48699	98.32594
Soil N (%)	0.07324	0.39152	0.03309	0.81382	99.13976
Soil P (mg/kg)	0.05599	0.36554	0.21226	0.62212	99.76189
Soil K (mg/kg)	0.02143	0.33787	0.33254	0.23811	100

Fig 6

Principal component analysis for studied soil and maize attributes using organic amendments as group.

Table 3

Eigenvalues, loadings, percentage of variance and cumulative of studied PCA attributes using fertilizers as group.

Principal Component	Eigenvalue	PC1	PC2	Percentage of Variance (%)	Cumulative (%)
		Loadings
Plant Height (cm)	6.02537	0.33159	0.24186	66.94852	66.94852
1000 Grains Weight (g)	1.58297	0.36776	-0.26377	17.58856	84.53708
Biological Yield (kg/ha)	0.47141	0.31081	-0.32268	5.23786	89.77494
Grain Yield (kg/ha)	0.36828	0.32512	-0.36128	4.09202	93.86696
Soil pH	0.26748	0.1462	0.66856	2.972	96.83896
Organic Matter (%)	0.13383	0.36064	-0.18326	1.48699	98.32594
Soil N (%)	0.07324	0.39152	0.03309	0.81382	99.13976
Soil P (mg/kg)	0.05599	0.36554	0.21226	0.62212	99.76189
Soil K (mg/kg)	0.02143	0.33787	0.33254	0.23811	100

Fig 7

Principal component analysis for studied soil and maize attributes using fertilizers as group.

Discussion

Results of the current study showed that both BC1 and VC1 sole and combined application imposed positive effects on maize growth and yield attributes i.e., plant height, 1000 grains weight, biological and grains yield. However, VC1+BC1 performance was significantly better than the sole application of these treatments. The improvement in the growth attributes was associated with improvement in soil organic matter and nutrient concentration by the application of BC1 and VC1. The porous structure of activated carbon sorp a significant amount of nutrients that reduced the losses of volatile nutrients (NH4+) thus improving the uptake of nutrients in the plants [34,35]. In addition, size, geometry, microspores, and distribution in biochar play a useful role in the absorption of water and nutrients. The addition of biochar also makes nutrients cycling speedy in soil. Higher holding of nutrients and rhizobacterial diversity enhance soil fertility and nutrient uptake in plants [36]. Chan et al. [37] argued that the high surface area of activated carbon is a major cause of improvement in cation exchange sites in the soil. Such improvements in exchange sites resulted in a better supply of nutrients to the crops. It also releases a significant amount of nutrients in soil solution that become part of the activated carbon structure during pyrolysis. The concentration of nutrients present in activated carbon is dependent on the type of waste feedstock that is used to develop the activated carbon [38]. Younis et al. [34] reported the better uptake of P by the addition of cotton sticks activated carbon. According to [39] biochar has a significant amount of potassium in ash. This potassium when dissolved in this soil water becomes readily available for plants. Ultimately uptake of potassium in plants is increased. Such better uptake of potassium plays a critical role in the osmoregulation and maintains the pressure in the guard cells due to which stomatal conductance is regulated [40,41]. Solid surface energy, dispersive and polar surface of biochar play a key role in the retention of water molecules when applied in soil. Biochar has negative surface charge due to negative zeta potential. This negative charge facilitates the electrostatic attraction of cations present in the soil. Such electrostatic attraction towards biochar provides a chance for the exchange of cations between salt solution and biochar surface [42]. Progressive degradation of cellulose and lignin in waste feedstock make the amorphous surface of biochar. This amorphous surface of biochar has micropores. The emission of volatile compounds during pyrolysis creates spaces that play a role in the absorption of water when biochar is applied in the soil as an amendment [43]. On the other hand, VC also has a high sorption ability for the essential nutrients in soil [44]. A significant proportion of N, P and K in vermicompost structure also played an imperative role in the enhancement of soil fertility. These nutrients become exchanged on the exchange sites of soil, thus their availability to plants is increased [45]. It has been observed that the beneficial soil microbial population is also significantly increased when vermicompost is applied. The readily organic contents in vermicompost facilitate the process of mineralization and nutrients cycling regulated by microbes in the soil. It also enhanced soil aeration and aggregation which played a key role in the proliferation of soil aerobic microbes [44,46]. Better aggregation also increases the water holding capacity. Plants usually take nutrients through this water uptake, thus better water availability by application of vermicompost also played important role in the improvement of crops productivity [44,46]. Similar results were also noted in the current study where soil N, P and K were significantly increased where VC was applied as a sole and combined amendment with BC and NPK.

Conclusion

It is concluded that both BC1 and VC1 have the potential to improve soil nutrient concentration when applied as an amendment in soil. BC1 and VC1 can improve maize growth and yield attributes as a sole amendment, however, their combined application in the presence of recommended NPK is a better strategy for enhancement of maize growth in poor organic matter soils. More investigations are suggested at the field level for declaration of VC1+BC1+NPK as the best amendment for enhancement in maize growth and yield in different agro-climatic zones.

10 Mar 2022

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Reviewer #1: Manuscript:

- Title: I would recommend rewriting it: Maize productivity and soil nutrients variations by the application of different vermicompost and biochar treatments, or something similar.

- Abstract:

Line 25: remove such

Line 26: remove the soil…

Line 27: remove That’s why…

Line 28: Four treatments were tested in the experiment:

Line 28: Four or eight treatments in total?

Line 29: NPK?

Lines 31-32: Why do they give two figures, what does each one mean?

Line 32: control without NPK?

Lines 34-35: It is recommended, it does not sound like the conclusion of a job, to rewrite the conclusion.

Lines 35-37: The best? compared to what? To rewrite.

- Introduction:

Lines 41: is a principal Kharif?

Line 45: an extra-space.

Lines 46-47: rewrite.

Line 48: One hundred g… After a point, write numbers with letters, here and throughout the text.

Line 58: remove and ash in different quantities.

Line 58: an extra-space.

Line 59: carbon evolution? What does it mean?

Line 73-75: rewrite.

- Materials and Methods:

Lines 82-83: rewrite sentence: Field trial was done in the Peshawar research farm, University of Agriculture, during summer 2020...

Lines 85-86: How many plants per treatment?

Line 86: cm. Maize…

Line 86: rewrite: Maize hybrid pioneer 3025w variety were used in the experiment…

Line 94: Eight treatments in total…

Line 111: 50 ml, 10 g, here and throughout the text.

Line 111: Then, the…

Line 112: shaking. After, the …

- Results: Add subheadings to the results section to make them easier to read and understand.

Line 138: BC1? not only VC1+BC1.

Lines 142-143: it is not clear what the author means.

Line 148-149: it would be better to give the averages together with the standard deviation obtained, it would be more useful data, and throughout the text.

- Discussion:

Line 252: pyrolysis. The

- Conclusions:

- Lines 287-288: Eliminate “Growers are recommended to apply VC1+BC1+NPK for the 287 achievement of better maize yield in low fertility status soils”, since you later mention that more studies are necessary to be able to ensure this.

- Figures:

Figures 1-4: edit them, they are very close together and it does not allow to analyze each graph separately. Also place letter of the figure outside of it.

Figure 5: Small edit significant differences.

Figure 6: This analysis was not done for the NKP?

Reviewer #2: 1. Why authors have selected these levels of vermicompost and biochar for study.

2. Give GPS location of the experiment.

3. No data is provided regarding the characterization of biochar and vermicompost. Please provide that.

4. How biochar was manufactured. Please elaborate.

5. From where vermicompost was collected. Either it was self-developed or commercial product. If it was commercial product then give batch number and manufacturer details.

6. Please provide details of N, P and K sources which were applied.

7. What was maize irrigation plan?

8. Give reference for the applied fertilizer dozes.

9. Please provide pre-experimental soil NPK data. Without that fertilizer application rates cannot be assessed.

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Reviewer #1: No

Reviewer #2: No

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Submitted filename: PONE-D-22-03141.docx

Click here for additional data file.

7 Apr 2022

REVIEWER 1 COMMENTS AND RESPONSES

- Title: I would recommend rewriting it: Maize productivity and soil nutrients variations by the application of different vermicompost and biochar treatments, or something similar.

Ans: Thank you for the suggestion. It is now modified accordingly.

- Abstract:

Line 25: remove such

Ans: It is now removed

Line 26: remove the soil…

Ans: It is now removed

Line 27: remove That’s why…

Ans: It is now removed

Line 28: Four treatments were tested in the experiment:

Ans: It is now corrected as per suggestions.

Line 28: Four or eight treatments in total?

Ans: There were 2 factors NPK and organic amendments. Four combinations of organic amendments were tested with and without NPK. It is now cleared in the manuscript.

Line 29: NPK?

Ans: It is now elaborated in full form and then abbreviations are used in the manuscript.

Lines 31-32: Why do they give two figures, what does each one mean?

Ans: It is because there were 2 comparisons one with NPK and the other without NPK i.e., BC0+VC0+NPK and control (BC0+VC0) respectively.

Line 32: control without NPK?

Ans: Yes, BC0+VC0 is a control that is without NPK.

Lines 34-35: It is recommended, it does not sound like the conclusion of a job, to rewrite the conclusion.

Ans: It is now modified as per the suggestion of the reviewer.

Lines 35-37: The best? compared to what? To rewrite.

Ans: It is now corrected as per suggestions.

- Introduction:

Lines 41: is a principal Kharif?

Ans: It is now corrected as per suggestion.

Line 45: an extra-space.

Ans: It is now corrected as per suggestion.

Lines 46-47: rewrite.

Ans: It is now corrected as per suggestion.

Line 48: One hundred g… After a point, write numbers with letters, here and throughout the text.

Ans: It is now corrected as per suggestion.

Line 58: remove and ash in different quantities.

Ans: It is now corrected as per suggestion.

Line 58: an extra-space.

Ans: It is now corrected as per suggestion.

Line 59: carbon evolution? What does it mean?

Ans: It is now corrected for more and clear understanding.

Line 73-75: rewrite.

Ans: It is now corrected as per suggestion.

- Materials and Methods:

Lines 82-83: rewrite sentence: Field trial was done in the Peshawar research farm, University of Agriculture, during summer 2020...

Ans: It is now corrected as per suggestion.

Lines 85-86: How many plants per treatment?

Ans: The dimensions are already provided which specified the plant population. However, from each plot minimum of 3 plants were maintained for the collection of data.

Line 86: rewrite: Maize hybrid pioneer 3025w variety were used in the experiment…

Ans: It is now corrected as per suggestion.

Line 94: Eight treatments in total…

Ans: It is now corrected as “Total four combinations of VC and BC were applied with and without NPK in three replicates”.

Line 111: 50 ml, 10 g, here and throughout the text.

Ans: It is now corrected as per suggestion.

Line 111: Then, the…

Ans: It is now corrected as per suggestion.

Line 112: shaking. After, the …

Ans: It is now corrected as per suggestion.

- Results: Add subheadings to the results section to make them easier to read and understand.

Ans: It is now corrected as per suggestion.

Line 138: BC1? not only VC1+BC1.

Ans: It is now corrected as per suggestion.

Line 148-149: it would be better to give the averages together with the standard deviation obtained, it would be more useful data, and throughout the text.

Ans: Thank you for your suggestion. However, all the graphs are already showing that data.

- Discussion:

Line 252: pyrolysis. The

Ans: It is now corrected as per suggestion.

- Conclusions:

- Lines 287-288: Eliminate “Growers are recommended to apply VC1+BC1+NPK for the 287 achievement of better maize yield in low fertility status soils”, since you later mention that more studies are necessary to be able to ensure this.

Ans: It is now corrected as per suggestion.

- Figures:

Figures 1-4: edit them, they are very close together and it does not allow to analyze each graph separately. Also place letter of the figure outside of it.

Ans: All the figures are software generated and are programmed at a specific pattern. We can not edit that becaused lettering is already selected outside the bars.

Figure 5: Small edit significant differences.

Ans: It is now corrected as per suggestion.

Figure 6: This analysis was not done for the NKP?

Ans: It is now corrected as per suggestion.

REVIEWER 2 COMMENTS AND RESPONSES

1. Why authors have selected these levels of vermicompost and biochar for study.

Ans: Organic amendments are gaining attention with each passing day. Poor soil organic matter is creating many problems for the achievement of better crops yield and productivity. On the other hand, increasing cost and health related issues of inorganic fertilizers are also creating the situation critical. That’s why to improve the soil health on sustainable basis and keeping in mind the environmental benefits current study was planned with the use of organic amendments biochar and vermicompost.

2. Give GPS location of the experiment.

Ans: Thank you so much for pointing out this mistake. The details are now incorporated as “The field experiment was established at research farm the University of Agriculture, Peshawar, Pakistan (34.1°’21” N, 71°28’5’E)”.

3. No data is provided regarding the characterization of biochar and vermicompost. Please provide that.

Ans: Thank you so much for pointing out this mistake. It is now provided as “Biochar produced had total C, N and P content of 67.3%, 1.03% and 0.21% respectively (C:N 65.34), pH 8.2”.

4. How biochar was manufactured. Please elaborate.

Ans: Thank you for your suggestion. The details are provided in the manuscript now as “Biochar was produced by pyrolysis of locally available mixed wood chips (hardwood) in a muffle furnace (450 ˚C for 4 h) and was grinded before applying to the field. The following reference is now also provided in the manuscript”

Irfan, M., Mudassir, M., Khan, M.J. et al. Heavy metals immobilization and improvement in maize (Zea mays L.) growth amended with biochar and compost. Sci Rep 11, 18416 (2021). https://doi.org/10.1038/s41598-021-97525-8.

5. From where vermicompost was collected. Either it was self-developed or commercial product. If it was commercial product then give batch number and manufacturer details.

Ans: Thank you for your suggestion. The details are provided in the manuscript now as “Crop residue and garden waste was used to prepare vermicompost. On partial composting, Eisenia fetida were introduced and the vermicompost (with pH 6.2, Total C 23.2%, Total N 1.30%, C:N 12.21, Total P 0.89%, mg kg-1 , bulk density 1.12 Mg m-3 and water holding capacity of 55.18%) was ready after 90 days.”

6. Please provide details of N, P and K sources which were applied.

Ans: Thank you for your suggestion. The details are provided in the manuscript now as “Basal dose of nitrogen (N), phosphorus (P) and potassium (K) was soiled @ 120-90-60 kg ha-1 from urea, single superphosphate and sulphate of potash. A full dose of P, K and ½ N were soiled just before sowing and incorporated/mixed and another ½ N was soiled after 35 days of the emergence of the crop with irrigation water. All the cultural and agronomic observes retained during the growing season”.

7. What was maize irrigation plan?

Ans: Thank you for your suggestion. The details are provided in the manuscript now as “During the maize growing season, six irrigation events were applied, with each event being equivalent to 75 mm, except the first (pre-planting) which was equivalent to 100 mm.”

8. Give reference for the applied fertilizer dozes.

Ans: Thank you for your suggestion. The details are provided in the manuscript now as “Khan, S.; Shah, Z.; Mian, I.A.; Dawar, K.; Tariq, M.; Khan, B.; Mussarat, M.; Amin, H.; Ismail, M.; Ali, S.; Shah, T.; Alamri, S.; Siddiqui, M.H.; Adnan, M.; Romman, M.; Fahad, S.; Nouman, A.; Kamal, A. Soil Fertility, N2 Fixation and Yield of Chickpea as Influenced by Long-Term Biochar Application under Mung–Chickpea Cropping System. Sustainability 2020, 12, 9008. https://doi.org/10.3390/su12219008.”

9. Please provide pre-experimental soil NPK data. Without that fertilizer application rates cannot be assessed.

Ans: Ans: Thank you for your suggestion. The details are provided in the manuscript in table 1.

Submitted filename: PONE-D-22-03141 Reviewer Response.docx

Click here for additional data file.

11 Apr 2022

Maize productivity and soil nutrients variations by the application of vermicompost and biochar

PONE-D-22-03141R1

Dear Dr. Danish,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Shahid Farooq, Ph.D.

Academic Editor

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Additional Editor Comments (optional):

Thank you for addressing the comments. I am pleased to accept your manuscript for publication in Plos One.

Reviewers' comments:

3 May 2022

PONE-D-22-03141R1

Maize productivity and soil nutrients variations by the application of vermicompost and biochar

Dear Dr. Danish:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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on behalf of

Dr. Shahid Farooq

Academic Editor

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