Oue et al. (2025) Effects of two types of mulch on evapotranspiration, dry matter, and water use efficiency of soybean under different soil water content

Identification

• Journal: Journal of Agricultural Meteorology
• Year: 2025
• Date: 2025-12-25
• Authors: Hiroki Oue, May Myat Mon, Y Zaw
• DOI: 10.2480/agrmet.d-25-00025

Research Groups

• Graduate School of Agriculture, Ehime University, Japan
• The United Graduate School of Agricultural Sciences, Ehime University, Japan

Short Summary

This study investigated the effects of white clover living mulch (CL) and shredded paper mulch (SP) on soybean growth, evapotranspiration (ET), and water use efficiency (WUE) under five different soil water content (SWC) levels in a pot experiment. Shredded paper mulch proved more effective for water-saving cropping systems, leading to better soybean growth and significantly higher WUE compared to clover living mulch, which increased ET due to clover transpiration.

Objective

• To clarify the effects of white clover living mulch and shredded paper mulch, and different soil moisture conditions, on biomass production, actual evapotranspiration (ET), and water use efficiency (WUE) of soybean [Glycine max (L.) Merr.].

Study Configuration

• Spatial Scale: Pot experiment conducted in a glasshouse (7.2 m x 12.8 m) at Ehime University, Japan (33.83°N, 132.79°E). Clay pots had an inside diameter of 20.5 cm at the top, 17.5 cm height, and a volume of 3544 cm³. The soil surface diameter was 20.0 cm with a depth of approximately 14.0 cm. Planting density was 31.8 plants m⁻².
• Temporal Scale: The experiment ran from December 2019 to May 2020, with measurements analyzed until April 30, 2020. The soybean growth period was divided into three stages:
  • Stage 1 (Vegetative, V1 to V6): December 27, 2019 - February 13, 2020 (Days After Transplanting 14-62).
  • Stage 2 (Beginning flowering R1 to beginning pod R3): February 14 - March 19 (Days After Transplanting 63-97).
  • Stage 3 (Full pod R4 to beginning maturity R7): March 20 - April 30 (Days After Transplanting 98-139).

Methodology and Data

• Models used:
  • Makkink equation (Makkink, 1957) was used to calculate daily potential evaporation (Ep): Ep = 3.6 Δ St / [Lv (Δ + γ )] Lv = 2499 ‒ 2.512 Ta where Δ is the slope of the saturated vapor pressure curve at air temperature (Ta), St is solar radiation, Lv is the heat of vaporization, and γ is the psychrometric constant (0.66 hPa °C⁻¹).
• Data sources:
  • Observation:
    • Soybean plant height (PH), leaf area index (LAI), and aboveground dry matter (DM) of leaves, stems, seeds, and pods were measured.
    • White clover plant height (PH) was measured in CL pots.
    • Actual evapotranspiration (ET) was measured daily for 42 pots using a weighing method (net daily change in pot weight).
    • Soil water content (SWC) was monitored daily using a capacitance type soil moisture sensor (Model 5TE, METER, USA) with a hand-held reader (Model ProCheck, METER, USA).
    • Meteorological conditions (solar radiation (St), air temperature (Ta), relative humidity (RH)) were measured at 2.0 m height in the glasshouse using Model PYR and Model VP-3 sensors (METER, USA), recorded every minute by a data logger (Model Em50, METER, USA).
  • Experimental Setup: Soybean was grown in 50 pots (25 with white clover living mulch (CL) and 25 with shredded paper mulch (SP)). Additionally, bare soil (BS) pots were included for two SWC levels. Soil water content was manually controlled at five distinct levels (SWC-1 to SWC-5, from driest to wettest, corresponding to approximately 64-65% to near-saturated conditions).
  • Statistical Analysis: Bonferroni correction was applied to a double-sided t-test for multiple comparisons between treatments.

Main Results

• Soybean Growth: Shredded paper mulch (SP) generally resulted in better soybean growth (plant height, LAI, and dry matter) compared to clover living mulch (CL) across most soil water content (SWC) levels, particularly after the vegetative stage. With SP, optimal soybean growth occurred in moderate SWC conditions (SWC-2 to SWC-4), while with CL, it was best in higher SWC (SWC-5).
• Clover Growth: White clover in CL pots exhibited better growth in lower SWC levels (SWC-1 to SWC-3) compared to higher SWC levels, indicating a potential negative synergistic effect on soybean due to water competition in drier conditions.
• Evapotranspiration (ET): Actual ET was significantly larger with CL compared to SP across most SWC levels. For instance, the average ET in the whole period for SWC-4 was 2.59 mm/d for SP and 3.64 mm/d for CL. SP effectively conserved soil moisture by reducing soil surface evaporation, especially in drier conditions, whereas CL increased water consumption due to additional transpiration by the clover.
• Water Use Efficiency (WUE): Both total aboveground dry matter WUE (WUEtotal) and seed WUE (WUEseed) were consistently higher with SP than with CL across all SWC levels. The highest WUE for seed with SP (0.115 mg/g) was observed in the lowest SWC (SWC-1), while with CL, it was highest in the highest SWC (SWC-5) at 0.035 mg/g. This indicates SP's superior performance in water-saving cropping systems.

Contributions

• This study provides a novel comparison of living (white clover) and non-living (shredded paper) mulches on soybean growth, evapotranspiration, and water use efficiency under a wide range of five distinct soil moisture conditions.
• It demonstrates the effectiveness of shredded paper mulch as a sustainable water-saving technique, showing a synergistic effect of improved soybean growth and reduced evapotranspiration, leading to significantly higher water use efficiency.
• The research highlights the potential for negative synergistic water stress on soybean when using clover living mulch, particularly in drier soil conditions, due to inter-species competition for water.

Funding

• Japan Society for the Promotion of Science (23HP2004)

Citation

@article{Oue2025Effects,
  author = {Oue, Hiroki and Mon, May Myat and Zaw, Y},
  title = {Effects of two types of mulch on evapotranspiration, dry matter, and water use efficiency of soybean under different soil water content},
  journal = {Journal of Agricultural Meteorology},
  year = {2025},
  doi = {10.2480/agrmet.d-25-00025},
  url = {https://doi.org/10.2480/agrmet.d-25-00025}
}