Effect of mucilage on water properties in the rhizosphere monitored by 1H-NMR relaxometry

In this work, we used 1H NMR relaxometry to analyze the presence and properties of biohydrogels in soil. Mucilage in soil leads to a hierarchical pore structure, consisting of the polymeric biohydrogel network surrounded by the surface of soil particles. Water molecules entrapped in mucilage-containing soils revealed an accelerated bulk relaxation and a higher surface relaxivity in comparison with soils not containing mucilage. In model soils, we quantified the gel effect, here defined as the influence of mucilage on proton relaxation. The difference between transversal and longitudinal relaxation rates was plotted as a function of the reciprocal diameter of the model soil particles for soils containing and not containing mucilage. The gel effect was thereby characterized by an accelerated bulk relaxation and an accelerated surface relaxation, traduced respectively by an increased y-intercept and an increased linear coefficient for mucilage-containing soil.