Background and Aims Volumetric soil water content (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">${\theta }_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>θ</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation>) strongly regulates nutrient diffusion, particularly under drying conditions. This study investigates how plant-derived mucilage alters water retention and the effective diffusion coefficient (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">${D}_{s}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>s</mi> </msub> </math></EquationSource> </InlineEquation>) of calcium (Ca2⁺) in soils with contrasting textures (sand, sandy loam, and loam) under varying <InlineEquation ID="IEq3"> <EquationSource Format="TEX">${\theta }_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>θ</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation>. Methods We amended soils with maize mucilage at contents (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">${C}_{m}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>m</mi> </msub> </math></EquationSource> </InlineEquation>) of 0.0, 2.5, 5.0, and 7.5 mg/g adjusted them to three <InlineEquation ID="IEq5"> <EquationSource Format="TEX">${\theta }_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>θ</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation> levels. A 45Ca tracer and phosphor imaging were used to track Ca2⁺ diffusion over time. <InlineEquation ID="IEq6"> <EquationSource Format="TEX">${D}_{s}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>s</mi> </msub> </math></EquationSource> </InlineEquation> was estimated from the 45Ca distribution, allowing evaluation of mucilage effects on water retention and solute transport. Results Mucilage effects were strongly texture- and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">${\theta }_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>θ</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation>-dependent. In loam, mucilage enhanced <InlineEquation ID="IEq8"> <EquationSource Format="TEX">${\theta }_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>θ</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq9"> <EquationSource Format="TEX">${D}_{s}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>s</mi> </msub> </math></EquationSource> </InlineEquation> at the same soil matric potential (<InlineEquation ID="IEq10"> <EquationSource Format="TEX">${\psi }_{soil}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ψ</mi> <mrow> <mi mathvariant="italic">soil</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>); for example, at a <InlineEquation ID="IEq11"> <EquationSource Format="TEX">${\theta }_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>θ</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation> of 0.125 cm3/cm3 (<InlineEquation ID="IEq12"> <EquationSource Format="TEX">${\psi }_{soil}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ψ</mi> <mrow> <mi mathvariant="italic">soil</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> = <InlineEquation ID="IEq13"> <EquationSource Format="TEX">$-$</EquationSource> <EquationSource Format="MATHML"><math> <mo>-</mo> </math></EquationSource> </InlineEquation> 23,608 cm), <InlineEquation ID="IEq14"> <EquationSource Format="TEX">${D}_{s}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>s</mi> </msub> </math></EquationSource> </InlineEquation> increased by more than eightfold at the <InlineEquation ID="IEq15"> <EquationSource Format="TEX">${C}_{m}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mi>m</mi> </msub> </math></EquationSource> </InlineEquation> of 7.5 mg/g compared to the control. This was attributed to increased water retention and improved liquid connectivity. In sandy soil, mucilage increased <InlineEquation ID="IEq16"> <EquationSource Format="TEX">${\theta }_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>θ</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation> only at higher content but decreased <InlineEquation ID="IEq17"> <EquationSource Format="TEX">${D}_{s}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>s</mi> </msub> </math></EquationSource> </InlineEquation> due to an increased liquid viscosity, which impeded solute mobility. Sandy loam showed intermediate behaviour. Conclusion Mucilage modulates both soil water retention and nutrient diffusion in a texture-dependent manner. Its beneficial effects are most pronounced in finer-textured soils, while coarser soils require higher mucilage contents to observe similar improvements.

Experimental insights into mucilage-mediated nutrient diffusion in different soil textures

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2025年11月24日

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Bahareh Hosseini,
Meysam Cheraghi,
Daniel Sebastian Moser,
Maire Holz,
Valerie Pusch,
Rainer Remus,
Mohsen Zarebanadkouki

摘要

Background and Aims

Volumetric soil water content ( ${\theta }_{v}$ $θ_{v}$ ) strongly regulates nutrient diffusion, particularly under drying conditions. This study investigates how plant-derived mucilage alters water retention and the effective diffusion coefficient ( ${D}_{s}$ $D_{s}$ ) of calcium (Ca²⁺) in soils with contrasting textures (sand, sandy loam, and loam) under varying ${\theta }_{v}$ $θ_{v}$ .

Methods

We amended soils with maize mucilage at contents ( ${C}_{m}$ $C_{m}$ ) of 0.0, 2.5, 5.0, and 7.5 mg/g adjusted them to three ${\theta }_{v}$ $θ_{v}$ levels. A ⁴⁵Ca tracer and phosphor imaging were used to track Ca²⁺ diffusion over time. ${D}_{s}$ $D_{s}$ was estimated from the ⁴⁵Ca distribution, allowing evaluation of mucilage effects on water retention and solute transport.

Results

Mucilage effects were strongly texture- and ${\theta }_{v}$ $θ_{v}$ -dependent. In loam, mucilage enhanced ${\theta }_{v}$ $θ_{v}$ and ${D}_{s}$ $D_{s}$ at the same soil matric potential ( ${\psi }_{soil}$ $ψ_{soil}$ ); for example, at a ${\theta }_{v}$ $θ_{v}$ of 0.125 cm³/cm³ ( ${\psi }_{soil}$ $ψ_{soil}$ = $-$ $-$ 23,608 cm), ${D}_{s}$ $D_{s}$ increased by more than eightfold at the ${C}_{m}$ $C_{m}$ of 7.5 mg/g compared to the control. This was attributed to increased water retention and improved liquid connectivity. In sandy soil, mucilage increased ${\theta }_{v}$ $θ_{v}$ only at higher content but decreased ${D}_{s}$ $D_{s}$ due to an increased liquid viscosity, which impeded solute mobility. Sandy loam showed intermediate behaviour.

Conclusion

Mucilage modulates both soil water retention and nutrient diffusion in a texture-dependent manner. Its beneficial effects are most pronounced in finer-textured soils, while coarser soils require higher mucilage contents to observe similar improvements.