PhD project title: EPS-based solutions to increase soil structure and resilience to drought (# of pos: 14)

Topic background
Almost 40% of the total agricultural land in Europe is prone to soil degradation, at a moderate or even severe level. Climate change, accompanied by increasing temperatures and less frequent but more intense rainfall events accelerates soil degradation and further decreases the capacity of soils to store and release the water and nutrients required for plant growth. Soil aggregates, made of particles held together by cohesive forces and organic matter are the basic units that form the soil structure and determine the physical and mechanical properties of soil, including water retention, water movement and aeration. Microbial organisms and their metabolic products affect soil structure by binding loose soil particles into stable aggregates. In particular, extracellular polymeric substances (EPS), produced by soil microorganisms, are known to have positive effect on water retention and aggregate stability.

Therefore, agricultural strategies that enhance EPS production have the potential to improve soil structure and thus increase the ability of soil to store and provide water to plants during periods of drought.

Research challenges
Despite the recognition of the positive effect of EPS on soil structure and decades of research on the industrial potential of EPS (e.g. as bio lubricants, thickener and preservatives), the use of EPS-based products in agriculture as soil improver is still very limited. In addition, our knowledge on EPS composition, structure and function, is far from complete. Gaining understanding of the role of EPS in determining soil structure and aggregate stability and elucidation of the mechanisms that regulate the biosynthesis of EPS in soils, could enable the use of EPS-based solution in agriculture to improve soil structure and prevent soil degradation.

Objectives and methodology
The PhD project aims to elucidate the effect of different types of soil amendments (complex as well as more readily biodegradable substrates), and of varying carbon to nitrogen ratio’s on the development of microbial communities in the soil, particularly on EPS producing and degrading microbes. The ultimate goals of the project is to develop nature-based solutions to increase soil structure and resilience to drought. To reach this goal we will identify key microbial groups responsible in soils for EPS production. We will test abiotic conditions (i.e. C:N ratio, nutrient availability) that may trigger EPS formation and thus influence soil properties.