A quantitative method for the high throughput screening for the soil adhesion properties of plant and microbial polysaccharides and exudates

Understanding the structures and functions of carbon-based molecules in soils is an important goal in the context of soils as an ecosystem function of immense importance. Polysaccharides are implicated in maintaining soil aggregate status but have not been extensively dissected in terms of their structures and soil adhesion properties. This is largely because of the technical difficulties in identifying polysaccharide structures and quantifying any functional properties. Here, we describe the use of a novel nitrocellulose-based adhesion assay to determine the relative capacities for soil adhesion of over twenty plant and microbial polysaccharides that are likely to be present in soil and to contribute to organic matter content and properties. Weights of soil adhered to spots of known amounts of specific polysaccharides were quantified by scanning of the nitrocellulose sheets. The most effective polysaccharides identified from this survey included chitosan, beta-1,3-glucan, gum tragacanth, xanthan and xyloglucan. We also demonstrate that the soil adhesion assay is suitable to assess the soil-binding properties of plant exudates. The soil adhesion assay will be useful for the functional dissection of the organic matter components of soils and also of the factors involved in soil attachment to plant roots and in rhizosheath formation.