How does mucilage alter soil mechanical properties and soil penetration resistance to root growth?

• Applicant: Professor Dr. Harry Vereecken, since 4/2022
• Subject Area: Soil Sciences
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 439374140

A proper root system is vital for plants to anchor them in the soil and to deliver adequate nutrient and water supply for further plant development. Breeders have identified root systems as an important plant trait to increase crop yields under critical soil conditions. For optimization of root growth, it is beneficial to properly understand the underlying physical processes of root penetration in soil.In the past decades, studies could show that root elongation is negatively correlated with mechanical soil penetration resistance and it has been investigated how soil mechanical properties are affected by soil properties, such as soil compaction, soil type and water content. In recent years, studies emerged indicating that root exudates alter soil mechanical properties as well. While it has been intensively studied how root exudates affect chemical, hydraulic and biological processes in soil, still we miss a profound general understanding and a proper theory of the underlying mechanisms how root exudates alter soil mechanical properties.Aim of our proposed project is to combine experimental, imaging and numerical tools to bridge the knowledge gap between information about physico-chemical properties of pure mucilage and the effect of the respective root exudate on soil mechanical properties and thus finally to estimate soil penetration resistance to root growth under consideration of root exudates.We hypothesize that roots can actively engineer the mechanical properties of the rhizosphere. More specifically we expect that (a) mucilage can increase soil stability depending on the nature, concentration, origin and chemical compositions of the exudates; (b) mucilage can absorb large volumes of water and may locally increase the water content which may tend to reduce soil penetration resistance; (c) the way how the two mechanisms (a) and (b) interact in controlling overall soil penetration resistance strongly depends on soil type, texture, bulk soil water content, mucilage type, concentration and exudation rate. To address these hypotheses and to better understand the underlying processes we will set up experiments where we measure rheological properties. We will combine our measurements with analytical estimations, numerical modelling and microtomography to find an estimation of soil penetration, the plastic deformation zone and the compaction zone created during root growth. We plan to finally test and possibly improve the numerical estimations using experiments where penetration resistance of real roots of plant seedlings is measured while they are growing in soil at various conditions.In this way, we want to contribute to the bigger question about possible mechanisms that may help plants to react to changing environmental conditions.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Professorin Dr. Eva Kröner, until 3/2022