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. 2023 Mar 16;18(3):e0283137. doi: 10.1371/journal.pone.0283137

Effects of nitrogen, phosphorus and potassium formula fertilization on the yield and berry quality of blueberry

Xinyu Zhang 1, Shuangshuang Li 2, Xiaoli An 1, Zejun Song 1, Yunzheng Zhu 1, Yi Tan 1, Xiaolan Guo 3, Delu Wang 1,*
Editor: Sushanta Kumar Naik4
PMCID: PMC10019695  PMID: 36928292

Abstract

Through the application ratio of nitrogen (N), phosphorus (P) and potassium (K) in the field, L9 (33) orthogonal experimental design was used to study the effects of different N, P and K ratios on the yield and quality of blueberry fruit, aiming to optimize the amount of supplied fertilizers. The results showed that N, P and K fertilizer had different effects on fruit yield and quality, among which K fertilizer was the most important factor. Fertilization could significantly improve the yield and fruit quality of blueberry, and the average yield of fertilization treatment was 37.78% higher than that of the control group (CK). Even the treatment with the worst results F6 (N2P3K1), its single fruit weight, anthocyanins, total phenols, soluble solids and soluble protein content were 1.09, 1.32, 1.23, 1.08 and 1.21 times higher than the control (CK), respectively. Based on the comprehensive evaluation of principal component analysis and multi factor analysis of variance, the best fertilization combination for high-yield and good-quality blueberries was N1P2K2 (F2), that is, the best fertilization effect was that including N 100 g/plant, P2O5 25 g/plant, K2O 25 g/plant, applied in the form of ammonium sulfate (472 g/plant), superphosphate (41 g/plant) and potassium sulfate (40 g/plant), respectively.

Introduction

Nitrogen (N), phosphorus (P) and potassium (K) fertilizers are well-known mineral elements necessary for plant growth and development [1], and the application of fertilizers containing these elements can significantly improve the yield and quality of fruit trees [2]. However, in actual production, the proportion of N, P and K is often unbalanced due to the lack of scientific ratio, which affects the absorption and utilization of nutrients by plants, reduces the yield and quality, and increases the risk of nutrient loss and environmental pollution [3]. Reasonable ratio of N, P and K can significantly promote plant growth while relatively reducing the amount of various fertilizers [4]. In the application of proportion-based fertilization, the optimal ratio of N, P and K and the appropriate amount of application should be determined by combining the fertilizer requirement rule of species, fertilizer supply characteristic of growing soil, fertilizer effect and nutrient interaction rule [5]. However, due to the great differences in climate, soil fertility and texture, and crop varieties in China, the amount and proportion of N, P and K fertilizers applied have been greatly affected, and the situation of improper fertilizer use still exists [3]. Moreover, no fertilization model has been found to be suitable for all plants, fertilizers and regions [6].

The cultivated area and yield of blueberries in China have jumped to the first place in the world. Guizhou Province is one of the main producing areas, with an area of 15,000 hm2 and a yield of 85,000 tons, but the yield per unit area and quality are not high [7]. This is closely related to the cultivation technology of blueberry, especially to the substandard fertilization management technology of blueberry [8]. However, a scientific and reasonable fertilization method can effectively promote the growth of blueberry plants [9] and obtain blueberries with high quality and yield [10]. As blueberry is an oligotrophic species with shallow root system [11, 12], it prefers ammonium N [13] and has low requirements for P, K, Ca and Mg [14], so there is often a phenomenon of overapplying N fertilizer and underapplying P and K fertilizer. At the same time, due to the poor absorption capacity of its roots, it is sensitive to fertilization [15]. Insufficient or excessive fertilization affect negatively the yield and quality of blueberries [16], and the vegetative growth of blueberries is inhibited, or even damaged [17]. Previous studies have shown that fertilization has a significant effect on the yield and quality of blueberries. For example, applying wood compost to blueberries cannot only promote their growth and increase their yield [18], but also it can improve their fruit soluble solid content [19]. Albert et al. [10]pointed out that the application of N, P and K fertilizers could increase the anthocyanin content of blueberry fruits. Reasonable combination of N, P and K application can increase blueberry yield [14]. However, some studies have pointed out that applying conventional fertilizers without guidance, can lead to salt accumulation in soil and reduce the yield and fruit quality of blueberries [8]. Studies on combined application of N, P and K have been fruitful in crops and fruit trees [3, 20, 21]. However, researches on blueberry mainly focus on the effect of single-nutrient fertilizer, while there are few studies on the interaction between N, P and K and how they affect the yield and quality of blueberry.

Therefore, this paper takes 5-year-old rabbiteye blueberry cv. Brilliant plants, explores the ratio of N, P and K applied to blueberry in this region through orthogonal test, aiming to optimize the appropriate amount of blueberry fertilizer by using comprehensive evaluation and variance analysis, in order to provide technical support for economic fertilizer saving, yield and quality improvement, and standardized cultivation of blueberry.

Materials and methods

Experimental site

The experimental site is located in Wuyang hemp blueberry plantation, Xuanwei Town, Majjiang County, Guizhou Province, China, between 26°21′-26°31′N and 107°33′-107°47′E, which is characterized by subtropical monsoon humid climate. The annual average temperature is 15.7°C, the annual average precipitation is 1266 mm, and the annual average frost-free period is 293 days. At an average altitude of 670 m. The base soil was an acidic yellow type with pH 4.35–5.50, organic matter content 23.90 g•kg−1, total nitrogen (N) content 7.84%, total phosphorus (P) content 1.9%, and total potassium (K) content 28%.

Plant material

Five -year-old rabbiteye blueberry (Vacciniumvirgatum cv. Brightwell) plants with similar growth, were selected as the experimental material.

Experimental design

The experiment was carried out under field conditions. Fertilizers containing N, P and K doses at three doses for each nutrient. Each factor was set at three levels according to Guo et al. [22], and each treatment was set with three replicates, three plants for each replicate. the plantation distancesplant spacing was is 1.5m, and the plantation density is 4444 trees/ha. Non fertilized plants were used as control (CK), and the experiment adopted L9 (33) orthogonal design. The fertilizers used were ammonium sulfate (N 21.2%), superphosphate (P2O5 60.6%) and potassium sulfate (K2O 63.2%), all of high chemical purity. The field was averagely fertilized four times throughout the year: Early March (pre-bloom), Early May (before fruit production), Late August to Early September (after fruit production, flower bud differentiation stage) and Early December (reductive fertilizer). The fertilizers were applied into a trench 50 cm in length, 20 cm in width and 20 cm in depth on each side of the periphery of the tree canopy projection, mixed and covered with soil. The experiment started in December 2014, and the experimental design is shown in Tables 1 and 2.

Table 1. Test factor level (annual application rate).

factor factor A factor B factor C
level N(g/plant) P(g/plant) K(g/plant)
1 100(472) 50(83) 100(158)
2(1/2) 50(236) 25(41) 50(79)
3(1/4) 25(118) 12.5(21) 25(40)
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Table notes Data in parentheses are compound dosage g/plant.

Table 2. Treatments of N, P and K with their dosages on blueberry plants.

Code Treatment N(g/plant) P2O5(g/plant) K2O(g/plant)
F1 N1P1K1 100 50 100
F2 N1P2K2 100 25 50
F3 N1P3K3 100 12.5 25
F4 N2P1K2 50 50 50
F5 N2P2K3 50 25 25
F6 N2P3K1 50 12.5 100
F7 N3P1K3 25 50 25
F8 N3P2K1 25 25 100
F9 N3P3K2 25 12.5 50
CK N0P0K0 0 0 0
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Method of index determination

The sample collection

At the peak of ripening period, the fruits were collected from the periphery of trees, with three replicates per treatment and three plants per replicate, and 60 fruits were collected from each plant, which were brought back to the laboratory under ice bath condition in reserve.

Determination of fruit indexes

Single fruit weight was measured by using a 1/10000 scale; Yield per plant = number of blueberry fruits per plant * average weight per fruit. The anthocyanin content was determined according to the method of Barnes et al. [23]. The Folin-Ciocalteu reagent method was used to establish a standard curve with gallic acid as the standard substance, and the content was expressed as (mg/g FW) [24]. The flavonoid content was appropriately determined according to the method of Wolfe et al. [25], the standard curve was established with catechin as the standard substance, and the content was expressed as (mg/g FW). The soluble sugar content was determined by HPLC system, the titratable acid content was detected by ultra-fast liquid chromatography combined with photodiode array [26], and the soluble solid content was determined by handheld refractometer(SW20) [27]. The sugar-acid ratio is the ratio of soluble solids to titratable acids.

The data processing

Excel 2013 and SPSS 18 software programs were used for statistical analysis of the experimental data, ANOVA and least significant difference (LSD) were applied to compare the differences between different data groups, the K value and range R of different factors at different levels was calculated and the principal component analysis method for comprehensive evaluation was used.

Results

Effects of different formulations of fertilization on blueberry fruit yield

There were significant differences in the yield of blueberry fruits among different fertilization treatments. The weight of single blueberry fruit in fertilization treatment was higher than CK, and the most obvious effects were observed in F2 and F6 treatments, which gave 8.67% higher values than CK. The yield of blueberry per plant of fertilization treatment was significantly higher than that of CK, which was F2, F4, F8 and F9. The most effective was F2 treatment, which was 79.26% higher than CK. Range analysis showed that N2P3K2 and N3P3K2 were the best fertilizer combinations affecting the fruit weight and yield per plant of blueberry. According to the R value, the order of influence of the three factors on the single fruit weight and yield per plant of blueberry is P>N>K and P>K>N, respectively (Fig 1, Table 3).

Fig 1. Effects of different formulations of fertilization on blueberry yield.

Fig 1

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Figure notes Different lowercase letters in the figure indicate significant differences between treatments(P<0.05).

Table 3. Results and analysis of orthogonal experiment on fruit yield of blueberry.

Code N(A) P(B) K(C) Single fruit weight (g) Yield per plant (kg)
F1 1 1 1 2.00 1.68
F2 1 2 2 2.13 2.42
F3 1 3 3 2.10 1.63
F4 2 1 2 2.07 2.38
F5 2 2 3 2.06 1.63
F6 2 3 1 2.13 1.12
F7 3 1 3 1.97 1.63
F8 3 2 1 1.99 2.38
F9 3 3 2 2.07 1.83
CK 0 0 0 1.96 1.35
Singlefruitweight(g) K1 2.08 2.01 2.04 P>N>K
K2 2.09 2.06 2.09
K3 2.01 2.10 2.04
R 0.08 0.09 0.05
F value 5.024 6.005 2.618
Yieldperplant(kg) K1 1.91 1.89 1.73 P>K>N
K2 1.71 2.14 2.21
K3 1.95 1.53 1.63
R 0.24 0.61 0.58
F value 0.28 1.70 1.72
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Effect of different formula fertilization on blueberry fruit quality

Formula fertilization caused significant changes in the quality of blueberry fruit, with different effects. Among the eight main quality indicators, anthocyanin, total phenol, soluble solids, soluble sugar content and sugar: acid ratio increased overall, titratable acid content decreased overall, flavonoid and soluble protein content some increased and some decreased (Fig 2).

Fig 2. Effect of different fertilization formulas on blueberry fruit quality.

Fig 2

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Figure notes Different lowercase letters in the figure indicate significant differences between treatments(P<0.05).

Compared with CK, the anthocyanin content, total phenol content and soluble solid content of blueberry fruits treated with fertilizer increased by 9.5% ˜ 62.96%, 14.94% ˜ 31.03% and 5.89% ˜ 23.65% respectively (Fig 2A, 2B and 2E).

The effect of Fertilization on the sugar: acid ratio of blueberry fruit was similar to that of soluble sugar content. Except for treatment F6, the soluble sugar content and sugar: acid ratio in blueberry fruits of other fertilization treatments were higher than CK. The most obvious effect was treatment F2, which was significantly different from CK, 57.19% and 48.64% higher than CK respectively (Fig 2F and 2H). The effect of Fertilization on the titratable acid content of blueberry fruit is opposite to that of soluble sugar. Except for treatment F6, the titratable acidity of other fertilization treatments is lower than CK, but there is no significant difference with CK. The most obvious effect was that of treatment F9(17.07% lower than CK) (Fig 2G).

Except for treatments F5, F6 and F8, the flavonoid content of other fertilization treatments was higher than CK, of which treatment F2 was significantly higher (36.36%) than CK (Fig 2C). The effect of Fertilization on the soluble protein content of blueberry fruit is different from that of flavonoids. Except for treatments F1, F2, F3 and F4, the soluble protein content of other fertilization treatments is higher than CK, of which treatment F6 is significantly higher (20.59%) than CK (Fig 2D).

The range analysis showed that the optimal combination affecting the content of anthocyanins, total phenols, flavonoids, soluble protein, soluble solids, soluble sugar, titratable acidity and sugar acid ratio of blueberry fruits were N2P1K3, N3P3K1, N1P1K2, N3P3K1, N1P1K2 or N2P1K2, N3P2K2, N1P2K2 and N1P2K2, respectively. According to the R value, it can be judged that the order of influence of the three factors on the above-mentioned parameters of blueberry fruit is as follows: P>K>N,N>K>P, K>N>P,N>K>P,N>K = P,K>N>P,K>N>P and K>N>P, respectively. According to the F value, the three factors of N, P and K fertilizer had a very significant effect on the total phenol of blueberry fruit (P<0.01), and a significant effect on the soluble sugar content of blueberry fruit (P<0.05) (Table 4).

Table 4. Orthogonal test on results and analysis of orthogonal test on blueberry fruit quality.

Code N(A) P(B) K(C) Anthocyanin (mg/g) Total phenol (mg/g) Flavonoid (mg/g) Soluble protein (mg/g) Soluble solid (%) Soluble sugar (%) Titratable acidity (%) Sugar acid ratio
F1 1 1 1 2.07 1.11 0.236 0.61 12.00 7.04 0.40 29.75
F2 1 2 2 2.32 1.10 0.300 0.58 12.50 9.29 0.35 38.90
F3 1 3 3 2.78 1.08 0.237 0.52 12.50 6.31 0.37 33.55
F4 2 1 2 3.08 1.02 0.221 0.58 13.33 6.98 0.36 38.36
F5 2 2 3 2.25 1.00 0.207 0.76 12.00 6.26 0.38 32.41
F6 2 3 1 2.49 1.07 0.153 0.82 11.67 5.30 0.47 24.68
F7 3 1 3 2.80 1.07 0.256 0.75 11.83 7.15 0.41 28.82
F8 3 2 1 2.29 1.14 0.175 0.75 11.83 7.84 0.41 29.27
F9 3 3 2 2.38 1.13 0.238 0.75 11.33 8.54 0.34 34.15
CK 0 0 0 1.89 0.87 0.222 0.68 10.78 5.91 0.41 26.17
Anthocyanin(mg/g) K1 2.39 2.65 2.28 P>K>N
K2 2.61 2.29 2.59
K3 2.49 2.55 2.61
R 0.22 0.36 0.33
F value 0.199 0.592 0.565
Totalphenol(mg/g) K1 1.10 1.06 1.10 N>K>P
K2 1.03 1.08 1.08
K3 1.11 1.09 1.05
R 0.08 0.03 0.05
F value 1506.599** 166.362** 554.471**
Flavonoid(mg/g) K1 0.258 0.238 0.188 K>N>P
K2 0.194 0.227 0.253
K3 0.223 0.210 0.233
R 0.064 0.028 0.065
F value 6.205 1.239 6.768
Solubleprotein(mg/g) K1 0.57 0.65 0.738 N>K>P
K2 0.72 0.70 0.64
K3 0.75 0.70 0.68
R 0.18 0.05 0.098
F value 3.415 0.315 0.703
Solublesolid(%) K1 12.33 12.39 11.83 N>K = P
K2 12.33 12.11 12.39
K3 11.67 11.83 12.11
R 0.66 0.56 0.56
F value 0.923 0.481 0.481
Solublesugar(%) K1 7.55 7.06 6.73 K>N>P
K2 6.18 7.80 8.27
K3 7.84 6.72 6.57
R 1.66 1.08 1.70
F value 48.820* 18.844* 54.443*
Titratableacidity(%) K1 0.37 0.39 0.43 K>N>P
K2 0.40 0.38 0.35
K3 0.39 0.39 0.39
R 0.03 0.01 0.08
F value 0.526 0.19 4.042
Sugaracidratio K1 34.07 32.31 27.90 K>N>P
K2 31.82 33.53 37.14
K3 30.75 30.79 31.59
R 3.32 2.73 9.24
F value 1.336 0.872 10.054
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* indicates that the influence of factors reaches a significant level (P<0.05),

** Indicating that the influence of factors reached a very significant level (P<0.01).

Comprehensive analysis of the effect of formula fertilization on the yield and berry quality of blueberry

The yield and berry quality of blueberry were evaluated by principal component analysis. The results show that according to the principle that the eigenvalue is greater than 1, the cumulative contribution rate of the first three selected component factors reaches 78.89%. Among the three principal components, the characteristic value of the first principal component is 4.81, and the variance contribution rate is 48.14%, which mainly reflects the single plant yield, flavonoids, soluble protein, soluble solids, soluble sugar, titratable acid content and sugar: acid ratio. The second and third principal components mainly reflect the single fruit weight, anthocyanin and total phenol content (Table 5).

Table 5. Eigenvector load matrix of three principal components.

Yield or quality index Feature vector Feature vector Feature vector
The 1st principal component The 2nd principal component The 3rd principal component
Singlefruitweight 0.412 0.548 0.186
Yieldperplant 0.809 -0.134 0.218
Anthocyanin 0.442 0.724 -0.050
Totalphenol 0.442 0.109 0.774
Flavonoid 0.673 -0.460 -0.307
Solubleprotein -0.649 -0.007 0.583
Solublesolid 0.738 0.571 -0.140
Solublesugar 0.742 -0.498 0.420
Titratableacidity 0.838 -0.310 -0.109
Sugaracidratio 0.963 0.028 -0.108
Eigenvalue 4.814 1.737 1.337
Variancecontributionrate 48.141% 17.374% 13.374%
Accumulativecontributionrate 48.141% 65.515% 78.889%
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Taking the variance of each principal component as the weight, the comprehensive scores of the three principal components of blueberry fruit quality and yield indicators under 10 treatments were calculated and ranked. It was concluded that the effect of fertilization treatment F2 was better than other treatments, the effect of F4 treatment was ranked second (Table 6), and the data results of the second year also proved this conclusion (Table 7). In addition, the benefit-cost ratio of treating F2 and F4 is 16.13 and 15.87, respectively, so F2 treatment is the best.

Table 6. Comprehensive score and ranking of yield and quality indexes of blueberry fruit under different fertilization treatments (2015).

Code N(A) P(B) K(C) Score of the 1st principal component factor Score of the 2nd principal component factor Score of the 3rd principal component factor Comprehensive score Y Comprehensive score ranking
F1 1 1 1 46.66 6.35 -0.26 52.75 7
F2 1 2 2 58.35 5.86 -0.25 63.96 1
F3 1 3 3 50.62 7.66 -1.15 57.13 4
F4 2 1 2 56.96 8.04 -1.37 63.63 2
F5 2 2 3 48.62 6.97 -0.87 54.72 5
F6 2 3 1 39.86 7.41 -0.38 46.90 9
F7 3 1 3 45.80 6.69 -0.09 52.40 8
F8 3 2 1 47.20 5.94 0.43 53.56 6
F9 3 3 2 51.73 5.55 0.11 57.40 3
CK 0 0 0 41.07 6.00 -0.38 46.69 10
Y K1 57.95 56.26 51.07 K>P>N
K2 55.08 57.41 61.66
K3 54.45 53.81 54.75
R 3.49 3.60 10.59
F value 0.874 0.854 7.292
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Table 7. Comprehensive evaluation of the effects of nitrogen, phosphorus and potassium fertilization on the yield and quality of blueberry fruit(2016).

Code Single fruit weight (g) Yield per plant (kg) Anthocyanin (mg/g) Total phenol (mg/g) Flavonoid (mg/g) Soluble protein (mg/g) Soluble solid (%) Soluble sugar (%) Titratable acidity (%) Sugar acid ratio Comprehensive score Y ranking
F1 1.56 1.70 2.56 1.36 0.31 0.74 12.33 9.66 0.64 19.41 25.33 9
F2 1.53 2.00 3.15 1.65 0.31 0.83 13.33 10.96 0.50 27.24 30.34 1
F3 1.44 1.32 2.40 2.09 0.35 0.83 12.67 11.60 0.54 23.58 27.37 5
F4 1.50 1.10 3.84 2.39 0.37 0.83 13.83 11.38 0.55 25.58 29.28 2
F5 1.52 1.71 3.08 2.00 0.42 0.98 13.33 13.18 0.58 23.73 28.69 3
F6 1.60 1.53 1.55 2.35 0.38 0.96 12.00 9.74 0.66 18.26 25.40 8
F7 1.62 1.63 2.13 1.75 0.42 1.07 12.67 10.05 0.55 23.28 28.25 4
F8 1.54 1.69 2.60 2.40 0.38 1.15 12.50 12.65 0.67 18.71 26.13 6
F9 1.48 1.12 1.91 1.74 0.38 0.59 11.83 10.32 0.51 23.44 26.06 7
CK 1.49 1.10 2.05 1.17 0.26 0.62 11.13 10.18 0.60 18.67 22.76 10
Y K1 27.68 27.62 25.62 K>P>N
K2 27.79 28.39 28.56
K3 26.82 26.28 28.10
R 0.97 2.11 2.94
F value 0.642 2.575 5.638
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From the comprehensive score Y value, it can be seen that fertilization treatment is higher than CK treatment, indicating that formula fertilization can effectively promote the yield and berry quality of blueberry. Range analysis showed that the best combination affecting the yield and berry quality of blueberry was N1P2K2 treatment. According to the R value, the order of influence of the three factors on blueberry yield and berry quality is K>P>N (Table 6).

Discussion

The reasonable combination of N, P and K can effectively improve the yield and fruit quality of trees. Studies have shown that these nutrients and their interactions have a remarkable influence on citrus yield, quality and soil residual available nutrients [3]; The combined application of N, P and K can increase the yield and improve fruit quality of kiwifruit [28]. The reasonable application of N, P and K fertilizers can ensure the nutritional balance of blueberries and improve the fruit yield [22]. The results of this experiment indicate that the combined applications of different N, P and K levels have a significant impact on the yield and quality of blueberry. From the comprehensive perspective of all indicators, the impact of K Fertilizer on the yield and quality of blueberry fruit is greater than that of N and P fertilizer, which may be due to the lack of K in the soil of this region.

K fertilizer is the most important factor affecting fruit quality [29]. In accordance, we found that K fertilizer had the most significant effect on the increment of soluble sugar and the decrement of titratable acidity in blueberry fruit. There was also significant improvement of the flavonoid content and sugar: acid ratio. It is consistent with the results of Wu Zhengchao et al. [30] who studied the effect of K fertilizer on the soluble sugar, Vc and sugar: acid ratio. Since K can participate in the metabolism and transportation of sugar, it increases the sugar content of fruit [31], and also promotes the transformation of phenolic substances into flavonoids by activating metabolic enzymes. N fertilizer was the most important factor affecting the content of total phenol, soluble protein and soluble solid in blueberry, and the effect of factor N on the content of total phenol in blueberry fruit was highly significant (P<0.01). It was shown that the application of N fertilizer had a significant impact on the fruit quality of blueberry. It was shown that the P fertilizer has a relatively obvious effect on the formation of blueberry anthocyanins, which may be because P mediates the accumulation of anthocyanins in plants by participating in the expression of anthocyanin synthesis genes [32]. P is involved in the metabolism of plants [33], and applying more (but not excessive) P fertilizer can increase the yield of blueberry [34]. In this study, P fertilizer is the biggest factor affecting blueberry yield, but it has no significant impact, which is consistent with the results of Laford et al. [35], because blueberry has very low demands for P, and the P in the soil can meet its demand. When P content in soil is high, increasing P fertilizer will reduce blueberry yield and delay fruit maturity [36]. Therefore, in order to improve the yield and berry quality of blueberry, it is necessary to determine and apply the appropriate ratio of N, P and K fertilizer to achieve the effect of increasing yield and saving fertilizer.

Conclusion

The effects of different fertilization formula on blueberry fruit yield and quality were diverse, and its yield and quality may be high or low, but all treatments could improve them by different degrees. This is related to the amount and proportion of different fertilizers. Moreover, heavy fertilization does not mean that the yield and quality of blueberry fruits must be high. Only a scientific and reasonable fertilization ratio can result in high-yield and good-quality blueberries. Therefore, through comprehensive evaluation and variance analysis, this study concluded that the best combination of N, P and K fertilization formula for blueberry cultivation with high yield, quality and efficiency in this area was N1P2K2 (F2), that is, 100, 25 and 25 g/plant of N, P2O5 and K2O, respectively.

In conclusion, rational and optimized application of N, P and K fertilizer can achieve good-quality and high-yield of blueberry. In production practice, the optimal fertilization scheme should be determined according to the soil fertility status, referring to the optimal nitrogen, phosphorus and potassium fertilization amount in this study, and based on the principle of increasing N and K, and stabilizing P.

Data Availability

All relevant data are within the paper.

Funding Statement

Author thanks the National Natural Science Foundation of China (NSFC 31260192) for their financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Decision Letter 0

Sushanta Kumar Naik

28 Nov 2022

PONE-D-22-30089Effects of nitrogen, phosphorus and potassium formula fertilization on the yield and quality of blueberry fruitPLOS ONE

Dear Dr. Wang,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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We look forward to receiving your revised manuscript.

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Sushanta Kumar Naik, PhD

Academic Editor

PLOS ONE

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Additional Editor Comments:

Give justification that how a one-year trial conducting at a single experimental site is suitable to improve the production of blueberry outside that site.

Several experiments need to be conducted across different agroecosystems due to varying yield-impacting factors to conclude for its recommendation. How is your present investigation justify the fertilizer recommendation across the region?

Re-write the entire manuscript based on proper English usage or consult to a professional.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: I Don't Know

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: No

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This is a good attempt to show the importance of major nutrients in production and quality. However, some important aspects are missing in this manuscript which is mentioned below;

• What is the basis of selection of three levels of N, P and K (based upon the recommendation like optimum, sub-optimum or soil test values etc.), as no information was provided on the soil properties.

• Beside the primary nutrients, micro nutrient affects the quality very significantly, but nothing was informed in this aspect.

• The experiment was carried out in 2014, the result presented is based on one year data or else.

• The work was related with the application of N,P, K on yield and quality, but use/ recommendation of these fertilizer only, may create the imbalance of micro nutrient and other soil properties. Which is an important aspect that is missing

• Based upon comprehensive score, it was recommended that F2 is superior but F4 and F9 is second and third, F2 and F4 were very similar. So it is better to compare the benefit cost ratio also before recommendation.

Reviewer #2: In general, the manuscript needs extensive revision for English language and grammar by a professional.

Page 1, title: … and potassium fertilization formula on the yield and berry quality of blueberry Page 2, line 21: …of nitrogen (N), phosphorus (P) and potassium (P) in the field…

From this line and throughout the rest text you must use the above abbreviations for the three nutrients.

Page 2, line 23: blueberry fruits, aiming to optimize the amount of supplied fertilizers.

Page 2, line 28: Even the treatment with the worst results (N2P3K1), …

Page 2, line 30: times higher than the control, respectively.

Page 2, line 33: blueberries was that including N 100 g/plant, P2O5 25 g/plant, K2O 25 g/plant, applied in the form of ammonium sulfate (472 g/plant), superphosphate (41 g/plant) and potassium sulfate (40 g/plant), respectively.

Page 3, line 41: potassium are well-known mineral … development [1], and the application of fertilizers containing these elements can significantly improve the yield…

Page 3, line 43-51: These lines must be written better.

Page 3, line 58: but the yield per unit area and quality are not

Page 4, line 65: “…they often have the problem …potassium fertilizer.” What do you mean?

Page 4, line 68: fertilization affect negatively the yield

Page 4, line 69: and the vegetative growth of blueberries is inhibited, or even damaged [17].

Page 4, line 71: cannot

Page 4, line 72: but also it can improve their fruit…

Page 4, line 76: have pointed out that applying conventional fertilizers without guidance, can lead to salt accumulation in soil and reduce…

Page 4, line 77-78: Delete ‘by applying … habits [8].’

Page 4, line 80: single-nutrient fertilizer

Page 5, line 83: rabbiteye blueberry cv. Brilliant plants, explores

Page 5, line 85: test, aiming to optimize the

Page 5, line 90: 2.1 Experimental site

Page 5, line 91: Please add the geographic coordinates of this site

Page 5, line 92: which is characterized by subtropical

Page 5, line 95: Delete the second ‘soil’

Page 5, line 96-97: Express these values as per cent (%)

Page 5, line 98: 2.2 Plant material

Refer whether these plants were self-rooted or grafted. Were the trees trained with a single trunk or what?

Page 5, line 99: Five -year-old rabbiteye blueberry (Vaccinium ??? cv. Brightwell) plants

Page 5, line 101: 2.3 Experimental design

Refer the plantation distances among trees.

Page 5, line 102: …under field conditions. Fertilizers containing N, P and K doses at three doses for each nutrient, three …

Page 6, line 104: Non fertilized plants were used …

Page 6, line 105: The fertilizers used were…

Page 6, line 106-107: Delete the words ‘content’

Page 6, line 107: …63.2%), all of high chemical purity.

Page 6, line 109: Do you mean ‘fruit production’ or ‘fruit set’?

Page 6, line 110: What do you mean with ‘reducing fertilizer’?

Page 6, line 110-111: The fertilizers were applied into a trench

Page 6, line 112-113: canopy projection, mixed and covered with soil.

Page 6, line 113: What you mean with ‘carried out’?

Page 6, line 114: the experimental design is shown

Page 7, Table 2: There are not all possible N-P-K combinations (eg N3P3K3). How did you select these ones?

Page 7, Table 2: You have not explained what is orthogonal test design. Provide a relative reference.

Page 7, Table 2: I propose the following legend: Table 2. Treatments of N, P and K with their dosages on blueberry plants.

Page 7, Table 2: It would be better to present the doses of nutrients (N, P2O5, K2O) not the form of fertilizers (ammonium sulfate etc)

Page 7, line 126: The Folin-Ciocalteu…method was used to establish …. (mg/g FW)[23].

Page 7, line 128: Replace ‘modified’ with ‘determined’

Page 8, line 133: Refer the type and model of the refractometer device.

Page 8, line 136: …SPSS 18 software programs were used…

Page 8, line 137: ANOVA and least significant difference (LSD) were applied to compare

Page 8, line 138: Delete ‘calculate’

Page 8, line 139: levels was calculated and the principal …evaluation was used.

Page 8, line 141: Results and Discussion

Page 8, line 145: effects were observed in F2 and F6 treatments, which gave 8.67% higher values than ...

Page 8, line 149: best fertilizer combinations affecting the fruit weight and yield…

Page 9, line 152: P>K>N, respectively…

Page 9, line 154: Delete ‘This is the’

Page 9, line 156: The Table 3 repeats data that has been already

Page 9-10, line 156: In the Table 3, column ‘Code’, there is a Chinese character.

Page 10, line 160, 166, 168: sugar: acid

Page 10, line 172: titratable acidity of other

Page 10, line 173: but there is no

Page 11, line 174: effect was that of treatment F9 (17.07% lower than CK)(Fig 2. G)

Page 11, line 176-177: F2 was significantly higher (36.36%) than CK…

Page 11, line 180: is significantly higher (20.59%) than CK…

Page 11, line 187: on the above-mentioned parameters of blueberry fruit is…

Page 11, line 189: ,respectively. According…

Page 12, line 194: Effect of different fertilization formulas on blueberry fruit quality.

Page 12, line 196: Table 4. Orthogonal test on …

Page 13, line 199: yield and berry quality of blueberry.

Page 13, line 200: The yield and berry quality of blueberry were evaluated…

Page 14, line 203-204: Limit to two decimal digits

Page 14, line 212: treatments F2…

Page 14, line 213: were ranked second.

Page 14, line 215, 216, 218: and berry quality

Page 14, line 217: Delete ‘which was also F2’

Page 15, table 5: Titratable acidity

Page 16, line 223: yield and fruit quality of trees. Studies have shown that these nutrients and their…

Page 16, line 226: improve fruit quality

Page 16, line 233-234: it is not clear what you mean. Was the level of soil K in the region low?

Page 16, line 235-236: In accordance, we found that …

Page 16, line 237: titratable acidity in blueberry fruit. There was also significant improvement of the flavonoid…

Page 16, line 238 and 240: sugar: acid

Page 16, line 239: Delete ‘on’

Page 16, line 240: fertilizer on the soluble sugar content, Vc and sugar: acid ratio.

Page 16, line 241: Since K can participate in…

Page 17, line 242: sugar, it increases the sugar…promotes …

Page 17, line 246: Replace ‘extremely’ with ‘highly’

Page 17, line 246: It was shown that the

Page 17, line 248: It was shown that the

Page 17, line 252: and applying more (but not excessive) P fertilizer …

Page 17, line 252-253: Delete ‘but it does not mean adding excessive phosphorus fertilizer.’

Page 17, line 256: low demands for

Page 17, line 259: and berry quality of blueberry, it is necessary to determine and apply the appropriate…

Page 18, line 263: fertilization formula

Page 18, line 264: but all treatments could improve them by …

Page 18, line 265-266: Moreover, heavy fertilization does not mean …

Page 18, line 267: Replace ‘obtain’ with ‘result in’

Page 18, line 271-275: Replace ‘that is, the best … potassium sulfate’ with ‘that is, 100, 25 and 25 g/plant of N, P2O5 and K2O, respectively.’

Page 18, line 277-281: It is not clear what you mean here. Rewrite it better.

Page 19, references: All latin names of plants must be written in italics.

**********

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Reviewer #1: No

Reviewer #2: No

**********

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PLoS One. 2023 Mar 16;18(3):e0283137. doi: 10.1371/journal.pone.0283137.r002

Author response to Decision Letter 0

28 Jan 2023

We have consider all the suggestions and revised the manuscript as per reviewer comments. Response sheet is uploaded in separate file.

Attachment

Submitted filename: rebuttal letter.docx

Click here for additional data file. (233.7KB, docx)

Decision Letter 1

Sushanta Kumar Naik

13 Feb 2023

PONE-D-22-30089R1Effects of nitrogen, phosphorus and potassium formula fertilization on the yield and berry quality of blueberryPLOS ONE

Dear Dr. Delu Wang,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Mar 30 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Sushanta Kumar Naik, PhD

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: (No Response)

Reviewer #2: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: 1. Soil pH is in acidic range, so significant amount of the applied phosphorus may be fixed in soil, so, whether, it is good to apply P fertilizer directly without any soil amendments.

2. It is still not mentioned in the manuscript that, what is the basis of selection of three levels of N, P and K, How you get the level 1.

3. Selection of recommendation should be based on the B: C ratio or some other important aspects. Which is not mentioned clearly?

4. Presentation of results in figures and tables are complicated, so, if possible convert it in simple form.

Reviewer #2: There are yet some missing data as follows:

Materials and methods

If available, provide the mean nutrient status of tested plants before fertilizer treatments took place.

If available, provide data about the fertilizers applied the year before experimentation.

What were the plantation distances and plantation density (number of trees/ha) of the tested orchard?

What about canopy training system and mean height of the tested trees?

Page 2, line 11: Replace ‘plants’ with ‘species’

Page 2, bottom line: Replace ‘was’ with ‘were’

Discussion, line 11: Delete the word ‘fertilizer’

Conclusion, first line: …formula on blueberry fruit …

Conclusion, bottom line: …of increasing N and K, and stabilizing P.

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Reviewer #1: No

Reviewer #2: No

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PLoS One. 2023 Mar 16;18(3):e0283137. doi: 10.1371/journal.pone.0283137.r004

Author response to Decision Letter 1

16 Feb 2023

Dear Editor: Sushanta Kumar Naik and Dear reviewers:

Thank you very much for your useful comments and professional advice on our manuscript. We wish to give a sincere gratitude to referees for reviewing our paper carefully. These opinions help to improve academic rigor of our article, and we apologize for any inconveniences caused by these errors. We have modified the manuscript accordingly, and the response to the referees’ comments are listed point by point below:

Reviewer #1:

Comment 1: Soil pH is in acidic range, so significant amount of the applied phosphorus may be fixed in soil, so, whether, it is good to apply P fertilizer directly without any soil amendments.

Reply 1: Thanks for your comment. Although a large amount of phosphorus is fixed in the soil under acidic conditions, it is not the best to apply phosphorus fertilizer directly. Because applying only one kind of fertilizer will aggravate the imbalance of soil nutrients. Moreover, a large number of studies have shown that compared with the single application of nitrogen, phosphorus and potassium, the combined application can significantly improve the fertilizer utilization rate.

Comment 2: It is still not mentioned in the manuscript that, what is the basis of selection of three levels of N, P and K, How you get the level 1.

Reply 2: Thanks for your comment. Select the three factors of N fertilizer, P fertilizer and K fertilizer, and set three levels for each factor according to Guo et al. [22], which has been added to line 3 on page 3 of the manuscript.

Comment 3: Selection of recommendation should be based on the B: C ratio or some other important aspects. Which is not mentioned clearly?

Reply 3: Thanks for your suggestion. It is calculated that the benefit-cost ratio of treating F2 and F4 is 16.13 and 15.87, respectively, so F2 processing is more recommended, and the relevant content has been added to lines 16-17 on page 6 of the manuscript.

Comment 4: Presentation of results in figures and tables are complicated, so, if possible convert it in simple form.

Reply 4: Thanks for your suggestion. But I can't find a better way to show the results. If possible, I hope you can give me some advice.

Reviewer #2: There are yet some missing data as follows: Materials and methods

Comment 1: If available, provide the mean nutrient status of tested plants before fertilizer treatments took place.If available, provide data about the fertilizers applied the year before experimentation.What were the plantation distances and plantation density (number of trees/ha) of the tested orchard?What about canopy training system and mean height of the tested trees?

Reply 1: Thanks for your suggestion. We regret that we did not provide enough complete material information in the materials and methods section. First of all, the plantation distances and plantation density (number of trees/ha) of the tested orchard are 1.5m and 4444 trees/ha respectively, which have been added to lines 4-5 on page 3 of the manuscript. Secondly, as a response to the reviewers, we regret the lack of detailed data on the mean nutrient status of tested plants before fertilizer treatments took place, the data of the fertilizers applied the year before experimentation, the canopy training system and mean height of the tested trees. This is a mistake in our research. We will be more cautious in future research.

Comment 2: Page 2, line 11: Replace ‘plants’ with ‘species’.

Reply 2: Thanks for your suggestion. The relevant content has been revised in line 10 on page 2 of the manuscript.

Comment 3: Page 2, bottom line: Replace ‘was’ with ‘were’.

Reply 3: Thanks for your suggestion. The last line on page 2 of the manuscript has been revised.

Comment 4: Discussion, line 11: Delete the word ‘fertilizer’.

Reply 4: Thanks for your suggestion. Relevant contents are modified in line 11 of the discussion part of the manuscript.

Comment 5: Conclusion, first line: …formula on blueberry fruit …

Reply 5: Thanks for your suggestion. Relevant contents are revised in the first line of the conclusion of the manuscript.

Comment 6: Conclusion, bottom line: …of increasing N and K, and stabilizing P.

Reply 6: Thanks for your suggestion. The last line of the conclusion of the manuscript has been revised.

Attachment

Submitted filename: rebuttal letter.docx

Click here for additional data file. (16.8KB, docx)

Decision Letter 2

Sushanta Kumar Naik

3 Mar 2023

Effects of nitrogen, phosphorus and potassium formula fertilization on the yield and berry quality of blueberry

PONE-D-22-30089R2

Dear Dr. Wang,

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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Kind regards,

Sushanta Kumar Naik, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: (No Response)

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: (No Response)

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

**********

Acceptance letter

Sushanta Kumar Naik

7 Mar 2023

PONE-D-22-30089R2

Effects of nitrogen, phosphorus and potassium formula fertilization on the yield and berry quality of blueberry

Dear Dr. Wang:

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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Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Sushanta Kumar Naik

Academic Editor

PLOS ONE

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    Attachment

    Submitted filename: rebuttal letter.docx

    Click here for additional data file. (233.7KB, docx)
    Attachment

    Submitted filename: rebuttal letter.docx

    Click here for additional data file. (16.8KB, docx)

    Data Availability Statement

    All relevant data are within the paper.

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