Cheng et al. (2026) Extreme precipitation rapidly recharges desiccated deep soil and restores deep root water uptake in a rainfed apple orchard: Implications for water management in deep-rooted agroecosystems

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Date: 2026-11-05
• Authors: Yahui Cheng, 武正丽, Yining Liu, Yuexin Zhu, Xiaoyu Liu, Hongchen Li, Huijie Li, Tamir Kamai, Esteban Gabriel Jobbagy, Bingcheng Si, Asim Biswas
• DOI: 10.1016/j.agwat.2026.110921

Research Groups

• School of Hydraulic and Civil Engineering, Ludong University, Yantai, Shandong, China
• Agriculture Research Organization (ARO-Volcani), Gilat Research Center, Negev, Israel
• Grupo de Estudios Ambientales, IMASL, Universidad Nacional de San Luis & CONICET, San Luis, Argentina
• Department of Soil Science, University of Saskatchewan, Saskatoon, SK, Canada
• School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada

Short Summary

This study investigated how an extreme wet year (2021) impacted deep soil water recharge and subsequent water uptake by a rainfed apple orchard on the Loess Plateau. It found that extreme precipitation significantly replenished deep soil water, leading to a multi-year deep-soil water reserve and a shift in tree water uptake towards these deeper, re-wetted layers.

Objective

• To quantify the depth, magnitude, and persistence of deep soil water recharge following an extreme wet year and determine if this anomaly leads to a redistribution of root water uptake in a mature rainfed apple orchard.
• Principal hypotheses:
  • An extreme wet year will lead to increased water storage in previously desiccated deep soil.
  • There will be a greater contribution of water from the rewetted deep-soil interval to tree transpiration.

Study Configuration

• Spatial Scale: A 150 m × 25 m rainfed apple orchard (established 2005) in the Wangdonggou catchment (35°14′N, 107°41′E), Changwu County, Shaanxi Province, on the southern Loess Plateau, China. Soil water dynamics were monitored down to 20 m depth.
• Temporal Scale: Data collected during the growing seasons of 2017 (before the extreme wet year) and 2023 (two years after the extreme wet year). The extreme wet year was 2021, with 920 mm annual precipitation.

Methodology and Data

• Models used:
  • Modified Bayesian continuous isotope-mixing framework (derived from PRIME and CrisPy) for root water uptake (RWU) partitioning.
  • Penman-Monteith equation for reference evapotranspiration (ET0).
  • Dual crop coefficient approach (FAO Irrigation and Drainage Paper 56) for potential transpiration (Tp).
  • Linear regressions for seasonal soil water storage and daily actual vs. potential transpiration relationships.
  • One-way analysis of variance (ANOVA) and least significant difference (LSD) for statistical comparisons.
• Data sources:
  • Field measurements: Soil water content (gravimetric method from auger samples at 20 cm intervals down to 20 m), fine root distribution (root auger method), stem sap flow (Thermal Dissipation Probes - TDP on four trees), stable isotopes of soil and plant water (cryogenic vacuum distillation, Cavitron centrifuge, Isotope Ratio Mass Spectrometer - IRMS 253 Plus), Leaf Area Index (LAI-2200C Plant Canopy Analyzer).
  • Meteorological data: Daily precipitation, air temperature, solar radiation, relative humidity, and wind speed from the Changwu Agro-ecological Station (approximately 1.5 km from the study site).

Main Results

• The 3–10 m soil layer retained approximately 350 mm more water in 2023 than in the 2017 baseline, two years after the 2021 extreme wet year.
• The apparent wetting-front propagation rate was approximately 5 m yr⁻¹, which is about 25 times greater than previously reported piston-flow rates, suggesting rapid non-piston recharge.
• Despite a lower leaf area index (LAI) in 2023 (1.76 ± 0.47) compared to 2017 (2.42 ± 0.52), actual transpiration (Ta) increased from 213 mm in 2017 to 232 mm in 2023.
• The ratio of actual to potential transpiration (Ta/Tp) significantly increased from 0.57 ± 0.24 in 2017 to 0.78 ± 0.31 in 2023 (P < 0.05).
• Isotopic tracing revealed a shift in transpiration water sources: the contribution from 3–10 m soil layers increased from 50 ± 12% in 2017 to 62 ± 12% in 2023, while the contribution from the 0–3 m layer decreased from 42% to 24%.
• Fine roots were detected to 20 m in 2023 (compared to 14.2 m in 2017), with the proportion of fine roots below 10 m increasing from 3.3% in 2017 to 20.0% in 2023.

Contributions

• Quantifies the depth, magnitude, and persistence of post-wet-year deep-soil water storage in a mature commercial orchard, demonstrating that exceptional wet years can substantially replenish desiccated deep soil and create a multi-year deep-soil water reserve.
• Provides novel insights into how extreme wet years alter deep soil–plant water linkages and influence subsequent water use in deep-rooted rainfed agroecosystems.
• Connects deep-water retention with subsequent increased water uptake by mature apple trees, extending previous research focused primarily on recharge depth.
• Highlights the necessity for agro-hydrological models to represent episodic deep recharge during exceptionally wet years and track the resulting deep-soil water storage across subsequent years.
• Offers a basis for considering on-farm water-conservation practices, such as rainwater harvesting, micro-relief design, and conservation tillage, to enhance the capture and retention of episodic large rainfall inputs in deep-rooted rainfed agroecosystems.

Funding

• National Natural Science Foundation of China (Grant Nos. 42577364, 42577362, 42507426)
• Natural Science Foundation of Shandong Province (Grant Nos. ZR2025MS597, ZR2024QD065, ZR2025QC410)
• Science and Technology Innovation Development Plan of Yantai City (Grant No. 2024JCYJ078)

Citation

@article{Cheng2026Extreme,
  author = {Cheng, Yahui and 武正丽 and Liu, Yining and Zhu, Yuexin and Liu, Xiaoyu and Li, Hongchen and Li, Huijie and Kamai, Tamir and Jobbagy, Esteban Gabriel and Si, Bingcheng and Biswas, Asim},
  title = {Extreme precipitation rapidly recharges desiccated deep soil and restores deep root water uptake in a rainfed apple orchard: Implications for water management in deep-rooted agroecosystems},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2026.110921},
  url = {https://doi.org/10.1016/j.agwat.2026.110921}
}