The effect of natural seed coatings of Capsella bursa-pastoris L. Medik. (shepherd’s purse) on soil-water retention, stability and hydraulic conductivity

Abstract

Myxospermous seeds become bound by mucilage upon hydration and this trait is ecologically important. Major impacts could be enhancing seed-soil contact and improving water retention, which we quantify in this study. Myxospermous or demucilaged seeds of Capsella bursa-pastoris L. Medik. (shepherd’s purse) were added to a test sandy clay loam at seed : soil densities of 5 and 10 % [w/w]. The soil water retention and hydraulic conductivity were assessed. Soil rheology was also assessed using extracted mucilage only amendment at 0.5 and 1 % [w/w]. Shepherd’s purse seeds increased soil water retention and reduced soil hydraulic conductivity for myxospermous and demucilaged seeds. Soil rheological properties (complex shear modulus, viscosity and yield stress) increased in response to seed mucilage addition, and became more pronounced as soil dried. The mucilage had greatest impact on the yield stress compared to the other rheology parameters. The densities of myxospermous and non-myxospermous seeds, and mucilage tested here reflect that may be found naturally in soil seedbanks. The findings provide the first evidence that the soil seedbank provided from a wild arable species may regulate the soil water retention and enhance soil stability, and that this capacity is greater for myxospermous seeds.