Abstract
Coastal saline–alkali soils represent one of the most challenging agroecosystems due to coupled chemical, physical, and biological constraints. Although humic acid (HA) and microbial fertilizers (MFs) are recognized as effective amendments, the mechanisms linking soil improvements to yield gains remain unclear. Here, a 2-year field experiment was conducted in the Yellow River Delta to assess the effects of HA, applied alone or in combination with Bacillus subtilis and Trichoderma harzianum, on soil salinity, nutrient availability, aggregate stability, microbial communities, and wheat yields. Results showed that HA application alone reduced soil electrical conductivity (EC) and total soluble salts (TSS), and enhanced aggregate mean weight diameter (MWD), leading to 40.94–55.64% higher yields. Co-application with MFs further amplified these improvements, lowering EC and TSS up to 77.04% and 73.83%, enhancing MWD by 122.50%, and raising yields by 75.79%. Soil enzyme activities (e.g., catalase, β-glucosidase, urease, and alkaline phosphatase) and fungal diversity were substantially enhanced, whereas bacterial diversity showed no significant change. Co-occurrence network analysis demonstrated that application of HA with MFs (particularly with B. subtilis) reshaped microbial networks by enriching modules linked to nutrient provisioning, aggregate stability, and enzyme activity, while suppressing modules associated with salinity tolerance. Keystone species such as Lysobacter and Massilia were significantly enriched and closely associated with soil chemical and aggregate improvements. Structural equation modeling further revealed that yield gains were mainly explained by reduced salinity and enhanced aggregate stability rather than nutrient provisioning. These findings provide mechanistic evidence that HA improves soil quality and wheat productivity in coastal saline–alkali soils through integrated chemical, physical, and biological pathways, and that these benefits are strengthened when combined with microbial fertilizers.
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Claims 14
Claim · model-written summary
Humic acid alone increased wheat yields by 40.94–55.64%.
- Taxon
- Wheat
Triticum aestivumt0 - Treatment
- HA application alonee1
- Outcome
- yieldse1
- Direction
- highere1
- Value
- 40.94–55.64%e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e1“HA application alone reduced soil electrical conductivity (EC) and total soluble salts (TSS), and enhanced aggregate mean weight diameter (MWD), leading to 40.94–55.64% higher yields”
Claim · model-written summary
Humic acid alone reduced soil electrical conductivity and total soluble salts in wheat fields.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- HA application alonee2
- Outcome
- soil electrical conductivity (EC) and total soluble salts (TSS)e2
- Direction
- reducede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e2“HA application alone reduced soil electrical conductivity (EC) and total soluble salts (TSS)”
Claim · model-written summary
Humic acid alone enhanced aggregate mean weight diameter in wheat fields.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- HA application alonee3
- Outcome
- aggregate mean weight diameter (MWD)e3
- Direction
- enhancede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e3“HA application alone reduced soil electrical conductivity (EC) and total soluble salts (TSS), and enhanced aggregate mean weight diameter (MWD)”
Claim · model-written summary
Co-application with microbial fertilizers lowered EC by up to 77.04%.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Co-application with MFse4
- Outcome
- ECe4
- Direction
- loweringe4
- Value
- 77.04%e4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e4“Co-application with MFs further amplified these improvements, lowering EC and TSS up to 77.04% and 73.83%”
Claim · model-written summary
Co-application with microbial fertilizers lowered TSS by up to 73.83%.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Co-application with MFse5
- Outcome
- TSSe5
- Direction
- loweringe5
- Value
- 73.83%e5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e5“Co-application with MFs further amplified these improvements, lowering EC and TSS up to 77.04% and 73.83%”
Claim · model-written summary
Co-application with microbial fertilizers enhanced aggregate mean weight diameter by 122.50%.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Co-application with MFse6
- Outcome
- MWDe6
- Direction
- enhancinge6
- Value
- 122.50%e6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e6“Co-application with MFs further amplified these improvements, lowering EC and TSS up to 77.04% and 73.83%, enhancing MWD by 122.50%”
Claim · model-written summary
Co-application with microbial fertilizers raised wheat yields by 75.79%.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Co-application with MFse7
- Outcome
- yieldse7
- Direction
- raisinge7
- Value
- 75.79%e7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e7“Co-application with MFs further amplified these improvements, lowering EC and TSS up to 77.04% and 73.83%, enhancing MWD by 122.50%, and raising yields by 75.79%”
Claim · model-written summary
Soil enzyme activities were substantially enhanced in wheat soils.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- Soil enzyme activitiese0
- Direction
- substantially enhancede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e0“Soil enzyme activities (e.g., catalase, β-glucosidase, urease, and alkaline phosphatase) and fungal diversity were substantially enhanced”
Claim · model-written summary
Fungal diversity was substantially enhanced in wheat soils.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- fungal diversitye0
- Direction
- substantially enhancede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e0“Soil enzyme activities (e.g., catalase, β-glucosidase, urease, and alkaline phosphatase) and fungal diversity were substantially enhanced”
Claim · model-written summary
Bacterial diversity showed no significant change in wheat soils.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- bacterial diversitye0
- Direction
- no significant changee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e0“whereas bacterial diversity showed no significant change”
Claim · model-written summary
Application of HA with microbial fertilizers enriched microbial network modules linked to nutrient provisioning, aggregate stability and enzyme activity.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- application of HA with MFse0
- Interactor
- B. subtilis
Bacillus subtilise0symbiont - Outcome
- modules linked to nutrient provisioning, aggregate stability, and enzyme activitye0
- Direction
- enrichinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e0“application of HA with MFs (particularly with B. subtilis) reshaped microbial networks by enriching modules linked to nutrient provisioning, aggregate stability, and enzyme activity”
Claim · model-written summary
Application of HA with microbial fertilizers suppressed microbial network modules associated with salinity tolerance.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- application of HA with MFse0
- Interactor
- B. subtilisBacillus subtilise0symbiont
- Outcome
- modules associated with salinity tolerancee0
- Direction
- suppressinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e0“application of HA with MFs (particularly with B. subtilis) reshaped microbial networks by enriching modules linked to nutrient provisioning, aggregate stability, and enzyme activity, while suppressing modules associated with salinity tolerance”
Claim · model-written summary
Keystone species Lysobacter and Massilia were significantly enriched and closely associated with soil chemical and aggregate improvements.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- Lysobacter and Massiliae0
- Direction
- significantly enrichede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e0“Keystone species such as Lysobacter and Massilia were significantly enriched and closely associated with soil chemical and aggregate improvements”
Claim · model-written summary
Yield gains were mainly explained by reduced salinity and enhanced aggregate stability rather than nutrient provisioning.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- yield gainse0
- Qualifier
- mainly explained by reduced salinity and enhanced aggregate stability rather than nutrient provisioninge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat Yield”
e0“Structural equation modeling further revealed that yield gains were mainly explained by reduced salinity and enhanced aggregate stability rather than nutrient provisioning”
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