Review Reports - Biochar and Nitrogen Fertilizer Synergies: Enhancing Soil Properties and Jujube Fruit Quality in Saline–Alkali Orchards of Southern Xinjiang

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The general comments

Experimental layout & replication not fully reported. The authors stated “single-row micro-plots (nine trees per replicate), 10 m buffer,” but do not state how many replicates per treatment, nor blocking or randomization across the orchard. Clarify number of rows/blocks per treatment and how rows/trees were randomized and analyzed (plot-level vs tree-level).
- Figure caption shows n=3 per treatment (for soils), which is low for a field factorial; justify power or increase replication.
The authors in the manuscript specifies that bamboo-derived biochar (500 °C, BET surface area 31.26 m² g⁻¹, carbon content 73–77%) was used, the study does not provide a full physicochemical characterization of the material. For reproducibility and to strengthen the agronomic interpretation, a comprehensive description is needed, including pH, electrical conductivity, ash content, volatile matter, fixed carbon, elemental composition (C, H, O, N, S), atomic ratios (H/C, O/C), bulk density, particle size distribution, functional groups (e.g., FTIR, XPS), and mineral/metal content (Ca, Mg, K, Na, heavy metals). These parameters are standard in high-impact biochar research and are essential to link biochar properties mechanistically with soil amendment effects. I strongly recommend including such characterization, either measured directly or clearly referenced with data from the supplier, to meet the methodological rigor expected in high-ranking journals.
The Statistics need to reflect the factorial, repeated-year nature such as methods specify one-way ANOVA + Duncan; with 3 biochar × 5 N × (potentially 2 years) you need at least two-/three-way ANOVA or mixed models (Year as random; Biochar, N, and their interaction fixed). Also specify assumption checks (Shapiro/Levene), multiple-testing control (e.g., Holm), and provide effect sizes + 95% CIs.
The soil sampling scheme is narrow for saline-alkali diagnosis. We noted that soil sampled once, 20–60 cm depth; saline stress and remediation are often strongest near the surface. Add 0–20 cm (and ideally 60–100 cm) layers, and report salinity metrics ECe, SAR, and especially ESP (you currently report pH/EC and ions but not ECe/SAR/ESP explicitly).
Microbiome methods/reporting incomplete
- Good that 16S (V3–V4) and ITS1 were sequenced with QIIME2-DADA2, but missing reads per sample, filtering thresholds, rarefaction depth/coverage %, database versions, and accession numbers. Provide SRA/ENA accession and a metataxonomic QC table (reads, ASVs/OTUs, coverage).
- PCoA variance explained looks suspiciously high (PC1 58% + PC2 42% = 100% for bacteria; similar for fungi). Please recompute and report exact eigenvalues/percentages, or correct the description.
The authors should clarify the fruit quality sampling/replication for example the authors collected 30 fruits per treatment; specify how many trees/plots these came from, whether fruits were pooled or analyzed as true biological replicates, and how within-plot pseudoreplication was handled.
In Results, the authors reported SS increases of 5.23–27.98% (BC2+NI-N) vs other combinations, but Conclusions state “87.53% increase over the control.” Resolve this discrepancy and ensure one quantitative statement.
The authors should check out the Figures, captions, and units and ensure all figures display n, error bars (SE or 95% CI), letters from the correct post-hoc, axis units, and treatment codes decoded in captions. Currently some captions note letters and n=3; standardize across all plots.
The correlation heatmap is descriptive; consider SEM (structural equation modeling) or piecewise regression to link Biochar/N → soil chemistry & enzymes → microbiome → yield/quality, moving from correlation to plausible causal pathways.
Methodological precision for assays

Report units and temperatures for enzyme activities, QC (blanks, standards), instrument models for pH/EC; and specify any matrix interferences for colorimetry.

Rename section 3.1.2 (“Effects … on soil total nutrient content”) — it actually reports available nutrients (SOM, AHN, AP, AK). Correct the heading.
Standardize inhibitor nomenclature (NBPT = urease inhibitor; DMPP = nitrification inhibitor) the first time they appear in Abstract and Methods.
Replace qualitative phrases (“delayed the increase of EC”) with effect sizes and CIs; consider presenting ΔEC vs control for interpretability.
Check language/typos (e.g., “manganese (Mg)” vs “Mn”; “Ironother (Fe)”). Ensure correct symbols and SI units throughout.
In PCoA caption, the text mentions Bray–Curtis while the paragraph mentions weighted UniFrac—keep consistent and specify which was used.

Specific comments

2.2 Experimental design — replication & randomization:
“Nine trees per replicate” is given, but number of replicates per treatment and randomization/blocking are not stated. Add a CONSORT-style diagram of treatment layout (rows/blocks), and analyze at plot level to avoid pseudoreplication.

2.3 Soil sampling — depth resolution for saline soils:
Sampling only 20–60 cm misses surface salinity dynamics; add 0–20 cm (and optionally 60–100 cm) and calculate ECe, SAR, ESP to support “saline-alkali” classification.
2.4 Microbiome — report depth & accessions:
Provide reads/sample, post-QC depth, rarefaction depth, taxonomy DB (e.g., SILVA/UNITE) and version, and SRA/ENA accession.
2.5 Fruit quality — true replicates:
“Thirty fruits” per treatment: specify how many trees/plots they came from and whether measurements were pooled or analyzed per-tree; align the statistical unit with the experimental unit (plot).
2.6 Data analysis — modeling upgrade:
Replace one-way ANOVA with mixed models (Year × Biochar × N), declare primary outcomes (e.g., PY, VC), add effect sizes + 95% CI, and use Holm adjustment for multiple testing.
Fig. 1 caption — replication & error:
You note n=3; ensure all figures display n, error bars, and common-letters from the model-appropriate comparison.
3.4 Yield & quality — quantify gains consistently:
PY ↑ 24.23% (BC1+UI-N) is clear; ensure SS improvements are consistent between Results and Conclusions (avoid 27.98% vs 87.53% conflict).
PCoA — variance explained:
Recompute and report correct % variation for PC1/PC2, and match the distance metric (UniFrac vs Bray–Curtis) across text and caption.
Data availability — public repos:
Replace “available on request” with DOIs/links for raw data, code, and sequencing reads.

I have some concern about Materials & Methods

Experimental layout: number of replicates per treatment; blocking scheme; randomization; plot dimensions; analysis unit (plot vs tree).
Soil salinity diagnostics: ECe (saturation extract), SAR, ESP; layered sampling (0–20, 20–60, 60–100 cm) and timing (pre- and post-season).
Assay QC: enzyme units, temperatures, calibration curves, blanks/standards; instrument models for pH/EC explicitly.
Microbiome QC: read counts, rarefaction, taxonomic DBs, accession numbers, negative controls.
Statistics: mixed-model specification; assumption checks; multiple-testing correction; effect sizes/CIs; pre-registered primary endpoints.

And I have some concerns about the results

Model-based tables reporting fixed-effect estimates (Biochar, N, Biochar×N, Year) for soil, PY, VC, SS with effect sizes and 95% CI.
Consistency check: harmonize SS improvement numbers between sections.
Microbiome: add a sequencing summary (reads/ASVs per sample, rarefaction curves, Good’s coverage %) and a PERMANOVA table for community differences.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Title

Consider condensing and focusing on the main idea of the research.

Example: Biochar and Nitrogen Fertilizer Synergies: Enhancing Soil Properties and Jujube Fruit Quality in Saline-Alkali Orchards of Southern Xinjiang

Abstract

At lines 14 to 17, consider changing to “Saline-alkali soils in southern Xinjiang present significant challenges for sustainable jujube cultivation, necessitating innovative fertilization strategies to improve soil health and enhance fruit quality. This study investigated the synergistic effects of biochar-nitrogen (N) co-application on soil amelioration and the improvement of jujube quality in saline-alkali jujube orchards.”

At lines 24 to 26, consider changing to “Biochar-N co-application significantly enhanced soil available nutrients, with the BC1+UI-N treatment producing the most notable increase in soil organic matter within the BC1 group (9.20%-14.51% enhancement).’

At lines 26 to 29, consider changing to “Notably, the treatments modulated soil microelement profiles, suppressing potentially toxic Cu and Mn while enhancing the availability of beneficial Mg and Fe. Soil enzyme activities responded differently, with urease and sucrase activities reaching maximum levels under BC2+N1 and BC1+UI-N treatments, respectively.”

At lines 39 to 42, consider changing to “The established quantitative relationships provide a scientific foundation for the implementation of precision agriculture in arid saline-alkali regions, offering significant implications for sustainable specialty fruit production and soil health restoration in environmentally challenged agricultural systems.”

At lines 21 to 42, why do the authors bring an extensive text related to the results of the research? Where are the hypotheses, the aims of the study? Where are the methodologies used to evaluate each variable? Where are the statistical analyses? These parts must be included in the abstract section, even if only in a short sentence, as this information is critical.

Keywords

Try to put only the word. Your keywords are expressions, more than a simple word.

Example: Ziziphus jujuba Mill; Enzyme regulation; Precision fertilization; Soil amelioration; Fruit quality; Microbiome dynamics and Co-application

Introduction

At lines 51 to 53, consider changing to “This imperative is particularly acute in arid and semi-arid regions, exemplified by southern Xinjiang, China, where soil salinization poses a severe threat to agricultural productivity and sustainability [3].”

At lines 61 to 67, consider changing to “Biochar, a carbon-rich material derived from biomass pyrolysis, represents a promising soil amendment that effectively alleviates saline-alkali stress through its high porosity, cation exchange capacity (CEC), and stable carbon matrix, which enhance water retention, reduce Na+ toxicity, and improve aggregate stability [6]. When co-applied with N fertilizers, biochar exhibits synergistic effects, reducing N losses through the adsorption of ammonium (NH4+) and nitrate (NO3-) ions, while neutralizing soil acidification from urea hydrolysis due to its alkaline properties [7,8].”

At lines 71 to 72, consider changing to “These synergistic interactions enhance the carbon-nitrogen balance, elevate soil C:N ratios, drive organic matter mineralization, and extend the duration of N supply [11].”

At lines 79 to 82, consider changing to “Extensive research has validated the synergistic benefits of co-applying biochar and nitrogen across diverse agricultural systems. For instance, 30 t ha-1 biochar combined with 276 kg N ha-1 resulted in maize yields of 14,928 kg ha-1, with a nitrogen use efficiency (NUE) of 46.3% [11].

At lines 83 to 85, consider changing to “In saline-alkali rapeseed cultivation, 10 t ha-1 biochar with 20% reduced nitrogen maintained stable yields while decreasing the soil Na+ content by 12-15% [15, 16].”

At lines 85 to 91, consider changing to “Furthermore, co-application of biochar-N significantly optimizes soil structure and nutrient retention; specifically, 40 t ha-1 biochar with N increased the number of water-stable aggregates by 34.8% while enhancing macroaggregate N storage by 41.3% [17]. The porous structure adsorbs NH4+ and NO3-, reducing N leaching by 30-50%. Meanwhile, alkaline surfaces (pH 8-10) neutralize H+ from urea hydrolysis, thereby alleviating soil acidification [9,14]. However, interaction mechanisms between biochar and EENFs under saline-alkali conditions remain unclear.”

At lines 92 to 96, consider changing to “Despite the demonstrated potential of biochar and EENFs in ameliorating degraded soils and improving crop yields [18], jujube orchards in southern Xinjiang represent unique saline-alkali ecosystems where calcic horizons, high exchangeable sodium percentage (ESP > 15%), and perennial root system distributions may substantially modify co-application responses [19,20].”

At lines 105 to 109, consider changing to “Through the systematic integration of soil chemistry, microbial ecology, and plant physiology research, this study aims to establish scientifically robust and ecologically adapted fertilization strategies for arid saline-alkali orchard ecosystems. This endeavor provides critical theoretical foundations and practical guidance for improving soil health, enhancing the quality of jujube fruit, and promoting sustainable agricultural intensification in southern Xinjiang.”

The authors must make the study hypothesis more straightforward.

Materials and Methods

At lines 112 to 115, consider changing to “The field experiment was conducted at the First Company of the 224th Regiment in Kunyu City, Xinjiang Uygur Autonomous Region, China (37°16′N, 79°15′E), situated on the southern margin of the Taklamakan Desert, where abundant solar radiation and thermal resources are available.”

At 117 to 123, consider changing to “The trees exhibited uniform characteristics with heights ranging from 2.3 to 2.6 m, canopy diameters of 1.7–2.1 m, and were trained in a central leader system. The orchard was managed under standardized conventional practices, resulting in relatively uniform tree vigor and growth conditions. The experimental soil was classified as sandy loam, with a pH of 8.21, a bulk density of 1.62 g cm⁻³, an organic matter content of 7.59 g kg⁻¹, a total nitrogen content of 0.29 g kg⁻¹, and a total carbon content of 14.1 g kg⁻¹.”

At lines 135 to 137, consider changing to “Plots consisted of single-row micro-plots (nine trees per replicate, with a 10 m buffer between treatments and guard rows to minimize edge effects).”

At lines 157 to 159, consider changing to “Organic matter (SOM) content was quantified using the modified Walkley–Black method, which involves potassium permanganate oxidation and external heating.”

At line 174, consider changing to “2.4. Soil DNA extraction, PCR amplification, and Illumina MiSeq sequencing”

At lines 183 to 185, consider changing to “Raw sequencing data underwent quality filtering and demultiplexing based on index and barcode information, followed by the removal of barcodes.”

At lines 191 to 192, consider changing to “The harvested fruits were immediately placed in pre-labeled sampling bags, stored in sampling containers, and transported to the laboratory for analysis.”

In the Materials and Methods section, the soil was not classified according to Soil Taxonomy or WRB. The soil was only classified by texture or particle size. This information is fundamental for readers to understand the type of soil used in the study.

What experimental design was used? Was it a randomized complete block design? This is not clear in the text. How were the treatments applied? This information is also unclear. Please clarify the application method in the field, including whether it was a single application or multiple applications.

I was unable to determine the number of repetitions. You mention that the plots were single-row microplots with nine trees per replicate, but how many replicates were used in total? The replication information is unclear. You also say that fertilizers and biochar were mixed and applied in April. Was this in April 2023, April 2024, or both? This needs clarification.

Which other agronomic practices were applied? Please specify them. You state that soil samples were collected using an auger from 20 to 60 cm. This creates a 40 cm interval of soil, but which layer was effectively analyzed: the top 20 cm, the bottom 60 cm, or the entire 40 cm? Be more precise in your explanation.

You also mention that three representative trees were sampled per treatment. Were these three trees per block? How many blocks were there? You use the phrase “with consistent drilling depth.” What does this mean exactly? This isn't very clear and should be clarified.

Where are the citations for the methodologies associated with fruit sampling and quality assessment? The “p” in p-values should be italicized. Were the assumptions of normality, homoscedasticity, and others met with the statistical analyses?

Results

At lines 209 to 217, consider changing to “The combined application of biochar-N significantly influenced TC (Figure 1A). TC in the BC1 treatment group was significantly higher than that in the BC2 and CK groups, with increases of 12.4% and 4.7%, respectively (p < 0.01). Under BC1 conditions, the UI-N treatment exhibited the most significant TC increase, surpassing the N1 treatment by 8.30%. The BC1+N2 treatment achieved the highest TC, exceeding other biochar-N combinations by 2.04% to 6.53%. Notably, TC under N1, N2, UI-N, and NI-N treatments initially increased then decreased with increasing biochar application rates, with all peaks occurring at the BC1 level, indicating that moderate biochar application (BC1) represents a critical threshold for optimizing carbon sequestration.”

At lines 218 to 224, consider changing to “TN followed the order BC1>BC2>CK, with BC1 and BC2 groups showing increases of 21.42% and 6.41%, respectively, compared to the control (p<0.01) (Figure 1B). The BC1+N2 treatment yielded the highest TN, surpassing other treatments by 18.47% to 34.51%. Similar to TC patterns, TN under N1, N2, UI-N, and NI-N treatments exhibited an initial increase followed by a decline with increasing biochar rates, with peak values at the BC1 level. Among equivalent N treatments, BC1+N1 showed the most significant increase in TN, exceeding the UI-N and NI-N treatments by 6.45% to 7.65%.”

At lines 229 to 223, consider changing to “TK followed the pattern BC1>CK>BC2, with BC1 showing increases of 6.64% and 12.26% over CK and BC2 groups, respectively. The BC1+N1 treatment produced the highest TK, surpassing other treatments by 2.81% to 15.09%. Collectively, these results demonstrate that biochar application at the BC1 level effectively enhances the total nutrient content of the soil.”

At lines 237 to 239, consider changing to “Box plots display the median (center line), interquartile range (IQR, represented by the box edges), maximum and minimum values within 1.5 × IQR (whiskers), and outliers (individual points). Sample size: n =3 Per treatment.”

At lines 242 to 251, consider changing to “The BC1+UI-N treatment achieved the highest SOM within the BC1 group, exceeding the other treatments in the same group by 9.20% to 14.51% (P < 0.05). Among all biochar-N combinations, BC2+N1 yielded the highest SOM, surpassing other treatments by 15.89%-17.26%. AHN decreased in the order BC1 > BC2 > CK, with BC1 and BC2 groups showing increases of 35.69% and 39.11% over the control, respectively (Figure 2B). The BC1+N2 treatment produced the highest AHN, exceeding that of other treatments by 2.57% to 25.16%. Both individual applications of nitrogen fertilizer or biochar promoted AHN accumulation, with combined biochar-N applications at an appropriate biochar dosage demonstrating superior efficacy compared to single applications.”

At line 251, consider changing to “AP showed differential responses to the co-application of biochar-N (Figure 2C).”

At line 257, adding a comma after “N1” and before “and”.

At lines 266 to 268, consider changing to “Fertilizer application significantly affects the content of macro and trace elements in the soil (Figure 3). In the control group, N treatments reduced Ca and Cu, with N1 treatment showing the most significant decreases of 11.30% and 27.08%, respectively (p<0.05).”

At lines 270 to 272, consider changing to “UI-N and NI-N treatments significantly enhanced Mg and Fe, with NI-N producing the most significant increases of 11.18% and 23.98%, respectively.”

At lines 272 to 276, consider changing to “In the BC1 group, N1 and N2 treatments increased Ca and Cu by 3.95% and 30.35%, respectively, relative to N0, whereas UI-N and NI-N treatments showed decreasing trends. Biochar-N co-application generally enhanced Mn, Mg, and Fe, with the N1 treatment producing the most significant Mn increase (11.35%) and the UI-N treatment yielding the highest increases in Mg (7.83%) and Fe (17.77%).”

At lines 282 to 284, consider changing to “Overall, biochar-N co-application suppressed soil levels of Ca, Cu, and Mn, while enhancing those of Mg and Fe; Zn responses varied depending on the specific treatment combinations.”

At lines 286 to 294, consider changing to “Soil pH following N fertilizer application (Figure 4A) showed that in the control group, UI-N treatment decreased pH by 1.84% compared to N0 (p<0.05). In the BC1 group, N treatments reduced pH by 0.98% to 3.05% relative to biochar alone, with UI-N exhibiting the most significant reduction. The BC2 group showed the lowest pH under N2 treatment, with a 2.18% decrease compared to the N0 group. The effects of different N fertilizer types on pH followed the order: UI-N < N2 < N1 < NI-N. Notably, UI-N combined with biochar significantly decreased soil pH, whereas NI-N showed an increasing effect. The BC1+UI-N treatment resulted in the maximum pH reduction, decreasing by 1.49% to 2.69% compared to conventional N fertilizer-biochar combinations.”

At lines 301 to 304, consider changing to “The CK+NI-N treatment reduced EC by 5.32% to 38.83% compared to conventional N fertilizer treatments. Overall, the integrated application of biochar and urease inhibitor-type N fertilizer resulted in lower pH values and delayed the increase of EC compared to the application of N fertilizer or biochar alone.”

At lines 312 to 320, consider changing to “N fertilizer application universally enhanced URE, with increases of 4.22%-8.20%, 5.24%-14.12%, and 4.79%-19.17% in CK, BC1, and BC2 groups, respectively, compared to N0 treatments. URE increased progressively with the biochar application rate, with the BC2+N1 treatment achieving the maximum values, exceeding those of BC2+UI-N and BC2+NI-N by 13.72% and 21.70%, respectively. The efficacy of different N fertilizer types followed the order: N1 > N2 > UI-N > NI-N. Inhibitor-enhanced N fertilizers, combined with biochar, suppressed URE, with CK+UI-N and BC1+NI-N showing reductions of 2.66% to 23.25% and 2.33% to 19.23%, respectively, compared to conventional N fertilizer treatments.”

At lines 321 to 324, consider changing to “N treatments significantly enhanced SUC in the CK and BC1 groups, with increases of 19.23%-26.92% and 37.14%-40.00% relative to N0, respectively. In contrast, N2 and NI-N treatments in the BC2 group reduced activity by 13.04% and 19.57%, respectively.’

At lines 326 to 328, consider changing to “Treatment efficacy followed the order: UI-N > N2 > N1 > NI-N, with BC1+UI-N increasing activity by 2.08% to 68.97% compared to conventional N-biochar combinations.”

At lines 329 to 355, consider changing to “ALP and CAT displayed contrasting responses (Figures 5C and D). ALP was enhanced under UI-N and NI-N treatments, with increases of 6.25% to 10.00% in the CK group. The activity hierarchy among nitrogen treatments was as follows: UI-N > NI-N > N2 > N1. CAT increased by 9.40%-23.08% under N treatments in the CK group, but decreased by 6.12%-6.80% and 6.71%-18.12% under UI-N and NI-N treatments in BC1 and BC2 groups, respectively. The BC1+N2 treatment produced maximum CAT, exceeding BC1+UI-N and BC1+NI-N by 9.42% and 10.22%, respectively.”

At lines 341 to 351, consider changing to “Figure 6A shows that among the 456 shared ASVs across treatments, the control group with low N applications outperformed N0, with N1, UI-N, and NI-N treatments increasing the dominant bacterial populations by 7.59% to 15.40%. In contrast, N fertilization in the BC1 group decreased the dominant bacterial populations by 22.06% to 39.79% compared to biochar alone. The BC2 group showed similar declining trends except for N2 treatment, which yielded 2,186 ASVs. Under combined biochar-N co-applications, UI-N and NI-N treatments at the BC1 level demonstrated the most significant enhancement, increasing by 2.81% to 20.57% compared to N1. Notably, bacterial community abundance under N0 treatment exhibited a unimodal response to increasing biochar rates, peaking at the BC1 level, indicating that moderate biochar application (BC1) optimally promotes bacterial community diversification.”

At lines 361 to 364, consider changing to “The BC1+UI-N treatment exhibited the most pronounced fungal community response, reflecting the unique synergistic effect of urease inhibitor-enhanced N fertilizer combined with biochar on promoting the fungal community.”

At line 371, you state “(Chao1, Simpson, Pielou_e, Shannon, and Observed_species).” Is this sentence correct? Is the name “Pielou_e”? Please confirm this sentence.

At lines 375 to 377, consider changing to ‘Conversely, the N addition in the BC1 group exhibited adverse effects, with reductions in diversity indices as follows: Chao1 (8.81% to 22.92%), Simpson (0.49% to 1.45%), Pielou_e (2.75% to 10.47%), Shannon (3.84% to 13.29%), and Observed_species (8.64% to 22.35%).”

At lines 385 to 388, consider changing to “Under combined biochar-N application, the BC2+NI-N treatment achieved the highest Chao1 (136.33) and Observed_species (133.67) values. The BC1+UI-N treatment yielded the maximum Pielou_e (0.82) and Shannon (5.13) indices, while the BC1+NI-N treatment produced the highest Simpson index (0.95).”

At lines 398 to 415, consider changing to “In bacterial communities (Figure 9), the phyla Actinobacteria, Proteobacteria, Firmicutes, and Chloroflexi emerged as the dominant groups. In the CK, N fertilization reduced Actinobacteriota abundance by 11.07% to 26.40%, while enhancing Chloroflexi abundance by 3.87% to 20.68%. Conversely, UI-N and NI-N treatments in the BC1 group increased Actinobacteriota abundance to 54.01% and 63.32%, respectively, representing increases of 9.59% and 28.47% compared to the N0 treatment. This contrasting response pattern indicates that while inhibitor-based N fertilizer application alone decreased Actinobacteriota abundance, its combination with biochar significantly enhanced abundance, with the most substantial effect observed at the BC1 level. Acidobacteriota abundance exhibited a decreasing trend followed by an increasing trend with increasing biochar application. In contrast, Proteobacteria, Firmicutes, and Chloroflexi showed an increasing-then-decreasing pattern under UI-N treatment and continuous decline under NI-N treatment.

In fungal communities, Ascomycota dominated overwhelmingly (>90%), although response patterns varied among treatments (Figure 9B). N fertilization in the CK group reduced Ascomycota abundance by 0.25% to 11.30%, whereas the BC1 and BC2 groups showed increases of 0.10% to 3.65% and 1.67% to 3.36%, respectively. Under N1 and UI-N treatments, Ascomycota abundance increased with the biochar application rate, whereas the NI-N treatment produced the opposite effect.”

The combined application of biochar-N fertilizer significantly influenced jujube PY (p < 0.01, Figure 11A). PY performance across treatment groups followed the order: BC1 > BC2 > CK. In the CK group, N2 and UI-N treatments increased PY by 3.32% and 15.44%, respectively, compared to the N0 treatment. Within the BC1 group, all N treatments significantly enhanced PY with increases ranging from 11.63% to 17.00%, with UI-N demonstrating optimal performance. In the BC2 group, only the NI-N treatment resulted in a significant reduction in PY of 4.54%. The BC1+UI-N treatment achieved the highest PY, representing a 24.23% increase over CK+N0 and surpassing other biochar-N combinations by 0.38% to 8.06%.

At lines 446 to 464, consider changing to “VC exhibited highly significant differences among treatments (p < 0.01, Figure 11B), following the pattern BC1 > BC2 > CK. N fertilization in the CK group enhanced VC by 2.78%-11.95%. The BC1 group showed increases of 2.99% to 10.70%, with UI-N achieving the maximum enhancement. In the BC2 group, N1, N2, and NI-N treatments increased VC by 12.10%, 8.28%, and 9.84%, respectively. The BC1+NI-N treatment increased VC by 16.47% compared to CK+N0 and surpassed other biochar-N combinations by 1.50% to 14.77%.

SS similarly demonstrated highly significant variation (p < 0.01, Figure 11C). In the CK group, N1 and NI-N treatments increased SS by 41.24% and 40.71%, respectively. The BC1 group showed increases of 12.98% to 15.47% for N1 and N2, while UI-N and NI-N decreased by 9.40% to 14.46%.”

Why are you writing “Figure. X”? Why a period after “Figure”?

The “p” of the p-value must be in lowercase letters and in italic.

Example: You must include a space when writing “BC1 > BC2 > CK,” as “BC1>BC2>CK” is incorrect. Please verify that all the information mentioned above is accurate in all your text.

At lines 476 to 477, consider changing to “As illustrated in the Figure. 12, jujube PY exhibited positive correlations with TC, TN, SOM, AHN, AP, URE, and SUC (p ≦ 0.05).”

At lines 481 to 482, consider changing to “The fungal Shannon index was negatively correlated with the fungal Chao1 index, Ca, CAT, and SS (p ≦ < 0.05).”

Why are you now writing “p ≦ < 0.05”? Why not continue writing “p < 0.05”?

The figures are complicated to read; please increase the image resolution. The X and Y axes are almost imperceptible, and the legends are too small, which can confuse when interpreting the results. Standardize the font size across all graphs. Why did the authors choose to present the results using boxplots? Why not use bar charts instead?

Discussion

At lines 509 to 515, consider changing to “Jin et al. (2024) demonstrated in a 6-year field study that 1.5-3.0% biochar applications (equivalent to approximately 5,000 kg ha^-¹) provided an optimal balance between soil improvement and crop yield in saline-alkali paddy soils. This result corroborates the BC1 response observed in this study [31]. Moreover, relative to acidic systems, the pronounced alkalinity of biochar, combined with OH- released during urea hydrolysis, can further elevate the pH (>8) in the alkaline soils of southern Xinjiang, thereby intensifying the chemisorption of carbonate on organic carbon [32].”

Please confirm if this citation “Jin et al. (2024)” is proper. I think you should call the number related to the reference and then mention the year of publication.

At lines 517 to 523, consider changing to “When combined with urease inhibitor-based N fertilizer (UI-N) and nitrification inhibitor-based N fertilizer (NI-N), biochar exhibited distinct effects on soil enzyme activities, reflecting its dual roles in creating a favorable microenvironment and the inhibitory effects of the respective additives [33,34]. The observed increase in urease activity following biochar application can be attributed to its porous structure, which enhances the surface area for microbial immobilization. At the same time, macropores (>200 nm) provide moisture-stable niches for urease-producing microorganisms.”

At lines 529 to 523, consider changing to “This result suggests that the combination of conventional urea with a moderate biochar application may stimulate aerobic microbial activity, leading to increased reactive oxygen species production and, consequently, elevated catalase expression [37], which aligns well with the results observed under the BC1 biochar level in the present study.”

At lines 537 to 540, consider changing to “Furthermore, the use of inhibitor-based N fertilizers, which maintains a more stable ammonium concentration and mitigates pH fluctuations caused by rapid nitrification, may create a more favorable microhabitat for alkaline phosphatase activity [40].”

At lines 558 to 562, consider changing to “This dichotomy reflects bacteria's rapid exploitation of readily available nitrogen, potentially leading to the competitive exclusion of less efficient species, while fungi leverage their extensive enzymatic repertoire and hyphal networks to more effectively utilize complex carbon compounds within biochar matrices under Nitrogen-Enriched conditions [44,45].”

At lines 566 to 568, consider changing to “This enhancement can be attributed to Actinobacteriota's specialized metabolic capabilities for degrading recalcitrant organic compounds, which are abundant in biochar matrices [46].”

At line 580, the correct form is “achieved” not “achieving”.

At lines 615 to 616, consider changing to “This result may be attributed to the more pronounced ameliorative effects of biochar under saline-alkali stress [57].”

At lines 628 to 631, consider changing to “Urease catalyzes the hydrolysis of urea into ammonium nitrogen, whereas sucrase participates in the decomposition of carbohydrates. The synergistic action of these enzymes enhances the overall efficiency of nutrient cycling in soil [60].”

At lines 638 to 641, consider changing to “Similarly, the negative relationships between yield and soluble sugar content, as well as soil manganese content, imply that elevated manganese concentrations may disrupt sugar metabolism and photosynthetic efficiency [63].”

Conclusion

At line 651, change “co-applicationon” for co-application on”.

At lines 652 to 655, consider changing to “The results indicated that fruit yield and quality exhibited an explicit dependency on biochar and N inputs, with low biochar application rates combined with low N levels being more favorable for soil carbon and N accumulation.”

At 656 to 658, consider changing to “Specifically, the combination of low-dose biochar with urease inhibitor-amended nitrogen significantly increased the per-plant yield of jujube, exceeding the control by 24.23%.”

Comments on the Quality of English Language

The English language needs improvement. Some sentences should be restructured to enhance readability and interpretation, and some words are misspelled.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have revised the manuscript thoroughly and addressed all of the reviewers’ comments satisfactorily. The manuscript is now clear, scientifically sound, and meets the journal’s standards. I recommend that the paper be accepted in its present form for publication.

The authors should correct the references in the list based on the MDPI Guidelines.

Reviewer 2 Report

Comments and Suggestions for Authors

The figures still have low resolution, which makes it difficult to read and correctly visualize the information they contain.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf