Yang et al. (2026) Optimizing summer fallow management decreases oligotrophic bacterial abundance and enhances rain-fed wheat yield through water and fertilizer improvements

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Date: 2026-01-09
• Authors: Bin Yang, Haoying Wang, Lian-li Zhang, Li Li, Ting-liang LI
• DOI: 10.1016/j.agwat.2025.110099

Research Groups

• College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China
• Soil Health Laboratory in Shanxi Province, Taiyuan 030031, China

Short Summary

This study investigated how optimized summer fallow management practices, combining organic fertilizer, deep tillage, furrow-ridging, and plastic film mulching, enhance rain-fed winter wheat yield and soil quality in the Loess Plateau. It found that these practices significantly improved rainfall storage efficiency, increased grain yield by 26.3%, and shifted soil microbial communities from oligotrophic to copiotrophic dominance.

Objective

• To evaluate the effects of different water and fertilizer management practices on soil water storage and yield formation characteristics in dryland wheat fields of the Loess Plateau.
• To assess the succession characteristics of soil microbial communities under these practices.
• To clarify the interactions among precipitation accumulation, microbial community succession, and crop yield formation.

Study Configuration

• Spatial Scale: Field experiment conducted in Hongtong County (36°41′51″N, 111°52′49″E), China, representing a typical dryland agricultural system of the Loess Plateau. Experimental plots measured 80 m² (5 m × 16 m). The soil was identified as Calcaric Cambisol.
• Temporal Scale: Two-year field experiment from 2022 to 2024, encompassing three summer fallow periods (June–September) and two complete winter wheat growing seasons (October–May).

Methodology and Data

• Models used:
  • Partial Least Squares Path Modeling (PLS-PM)
  • Monte Carlo uncertainty analysis
  • Multiple linear regression model
• Data sources:
  • Field Experiment: Six treatments (Conventional Farmer Practice (FP), Organic Fertilizer (OF), Organic Fertilizer + Deep Tillage (OD), Organic Fertilizer + Deep Tillage + Furrow-ridging (ODR), Organic Fertilizer + Deep Tillage + Furrow-ridging + Plastic Film Mulching (ODRP), Organic Fertilizer + Deep Tillage + Furrow-ridging + Biodegradable Film Mulching (ODRB)) arranged in a randomized complete block design with three replicates.
  • Soil Samples: Collected from 0–2 m depth (for water content and nitrate nitrogen) and 0–40 cm depth (for available phosphorus and potassium) before sowing and after harvest. Samples from 0–20 cm depth were used for soil organic matter, total nitrogen, and microbial analysis.
  • Plant Samples: Winter wheat samples collected at maturity stage for yield indicators (grain yield, biological yield, spike number per hectare, kernel number per spike, 1000-grain weight, harvest index).
  • Microbial Analysis: 16S rRNA gene sequencing of the V4 hypervariable region (using primers 515 F and 806 R) from soil samples (0–20 cm depth) collected after harvest in 2024. Sequences clustered into Operational Taxonomic Units (OTUs) at 97% similarity and annotated using the SILVA 16S rRNA database.
  • Physicochemical Analyses: Soil water content (oven-drying at 105 °C), soil organic matter (wet oxidation-redox titration), nitrate nitrogen (KCl extraction, hydrazine sulphate method), available phosphorus (NaHCO₃ extraction, molybdenum blue colorimetric method), available potassium (ammonium acetate extraction, flame photometry), soil bulk density (cutting ring method), and pH (pH meter).
  • Meteorological Data: Temperature and precipitation data recorded during the experimental period.

Main Results

• Winter Wheat Yield: The optimized rainfall management (ODRP) significantly increased winter wheat grain yield by an average of 26.3 % compared to conventional farmer practice (FP), with spike number per hectare identified as the primary yield determinant.
• Water Storage and Use Efficiency: Average summer fallow rainfall storage efficiency under OF, OD, ODRP, and ODRB treatments exceeded FP by 4.5 %, 36.3 %, 48.1 %, and 27.0 %, respectively. ODRP maintained significantly higher water storage in the 0–60 cm soil layer. Annual precipitation utilization efficiency was highest under ODRP.
• Soil Organic Carbon (SOC): In 2024, ODRP and OF treatments increased SOC content in the 0–20 cm layer by 24.89 % and 18.30 %, respectively, compared to FP. In the 20–40 cm layer, most treatments (except OD) enhanced SOC stock by 39.11–46.70 % relative to FP.
• Soil Bacterial Community: Optimized management practices (OD, ODR, ODRP) significantly reduced the relative abundance of oligotrophic bacteria (Acidobacteriota by 14.19–26.10 % and Vicinamibacteria by 22.99–32.44 %). ODRP markedly increased the relative abundance of copiotrophic bacteria (Firmicutes) by 54.17–92.68 %.
• Yield Drivers: Correlation analyses showed significant positive associations among soil moisture, Firmicutes abundance, and winter wheat yield. Acidobacteriota abundance was negatively correlated with yield. Partial least squares path modelling identified soil moisture as the principal factor influencing yield formation via spike number, accounting for 63 % of the yield variability.
• Uncertainty Analysis: Monte Carlo simulations predicted a mean yield of 2606 kg/ha (95 % confidence interval: 2098.05–3096.64 kg/ha), with annual precipitation use efficiency (A-PUE) contributing 63.26 % to yield variation.

Contributions

• Provides a comprehensive integrated technical approach for sustainable and high-quality agricultural development in dryland wheat systems of the Loess Plateau.
• Demonstrates that combining early organic fertilizer application, deep tillage, furrow-ridging, and plastic film mulching during summer fallow synergistically improves soil water retention, enhances soil organic carbon sequestration, and promotes beneficial shifts in soil microbial communities.
• Quantifies the critical role of soil moisture and annual precipitation use efficiency as primary drivers of winter wheat yield in arid regions, offering data support for agricultural target setting and risk assessment.
• Elucidates the mechanism of yield enhancement through the modulation of soil microbial life-history strategies, shifting from oligotrophic (Acidobacteria) to copiotrophic (Firmicutes) dominance, indicating improved soil quality.

Funding

• National Key Research and Development Program of China (2023YFD1900402 and 2021YFD1900700)
• National Natural Science Foundation of China (42377356)
• Special fund for Science and Technology Innovation Teams of Shanxi Province (202304051001042)
• Shanxi Province Basic Research Program Project (202403021211198)
• Technology Innovation Enhancement Project of Shanxi Agricultural University Science (CXGC202414)
• Doctor Work station Project of Jinzhong Agri-cultural High-tech Zone (JZNGQBSGZZ002)

Citation

@article{Yang2026Optimizing,
  author = {Yang, Bin and Wang, Haoying and Zhang, Lian-li and Li, Li and LI, Ting-liang},
  title = {Optimizing summer fallow management decreases oligotrophic bacterial abundance and enhances rain-fed wheat yield through water and fertilizer improvements},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2025.110099},
  url = {https://doi.org/10.1016/j.agwat.2025.110099}
}