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

Abstract Background and Aims Volumetric soil water content ( $${\theta }_{v}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>v</mml:mi> </mml:msub> </mml:math> ) strongly regulates nutrient diffusion, particularly under drying conditions. This study investigates how plant-derived mucilage alters water retention and the effective diffusion coefficient ( $${D}_{s}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>D</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> ) of calcium (Ca 2 ⁺) in soils with contrasting textures (sand, sandy loam, and loam) under varying $${\theta }_{v}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>v</mml:mi> </mml:msub> </mml:math> . Methods We amended soils with maize mucilage at contents ( $${C}_{m}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>C</mml:mi> <mml:mi>m</mml:mi> </mml:msub> </mml:math> ) of 0.0, 2.5, 5.0, and 7.5 mg/g adjusted them to three $${\theta }_{v}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>v</mml:mi> </mml:msub> </mml:math> levels. A 45 Ca tracer and phosphor imaging were used to track Ca 2 ⁺ diffusion over time. $${D}_{s}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>D</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> was estimated from the 45 Ca distribution, allowing evaluation of mucilage effects on water retention and solute transport. Results Mucilage effects were strongly texture- and $${\theta }_{v}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>v</mml:mi> </mml:msub> </mml:math> -dependent. In loam, mucilage enhanced $${\theta }_{v}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>v</mml:mi> </mml:msub> </mml:math> and $${D}_{s}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>D</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> at the same soil matric potential ( $${\psi }_{soil}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>ψ</mml:mi> <mml:mrow> <mml:mi>soil</mml:mi> </mml:mrow> </mml:msub> </mml:math> ); for example, at a $${\theta }_{v}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>v</mml:mi> </mml:msub> </mml:math> of 0.125 cm 3 /cm 3 ( $${\psi }_{soil}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>ψ</mml:mi> <mml:mrow> <mml:mi>soil</mml:mi> </mml:mrow> </mml:msub> </mml:math> = $$-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>-</mml:mo> </mml:math> 23,608 cm), $${D}_{s}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>D</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> increased by more than eightfold at the $${