[AGRIFOOD] Characterisation of microbiotic soil crusts in arable soil and their effect on pesticide fate and persistence

Soil usually possesses a microbiotic crust at the surface, which is biologically formed and contains autotrophic algae and cyanobacteria. Since these layers form at the soil surface, they have considerable importance in determining water infiltration and evaporation, erosion and gas exchange. Current regulatory guidelines to assess the environmental fate of crop protection products (CPP) are conducted on processed (sieved) soil in the dark. Hence, any contribution of communities in the microbiotic layer to CPP degradation is not assessed. Collaborative work between Syngenta and Warwick has indicated that microbiotic layers at the surface of arable soils significantly enhance degradation rates of crop protection products (CPP). These findings suggest that the microbiotic layer could have a major role in determining the environmental fate of CPP which has previously been overlooked. The student will build on earlier Syngenta-Warwick research to investigate the mechanisms underlying altered degradation rates of pesticides in the microbiotic layer, the way in which environmental and crop characteristics affect development and characteristics of the microbiotic layer, and the consequences of this for CPP biodegradation and transport through soil. The following hypotheses will be tested: 1. Phototrophic organisms are responsible for enhanced rates of CPP biodegradation within the microbiotic crust 2. The structure and composition of the microbiotic crust changes seasonally 3. Crops showing different canopy characteristics have microbiotic crusts with different structure, composition and spatial distribution 4. Microbiotic crust structure and composition affects sorption of CPP and transport into soil 5. Structure and composition of the microbiotic crust affects CPP biodegradation The industrial partner will provide funding to allow the student to spend a 3 month placement at Syngenta during year 1, learning and applying advanced protocols to quantify CPP and bound residues using 14C methodologies. Following the experimental phase of the work the industrial partner will support the student to spend a further 3 month placement at Syngenta to determine the significance of microbiotic crusts for pesticide fate and persistence in soil under different crop types, using pesticide fate modelling approaches (e.g. FOCUS simulation models and scenarios) The studentship provides interdisiplinary training in soil science, microbiology and the environmental chemistry. Furthermore the supervisors have an established collaborative programme, with Bending, Schafer and Marshall already co-supervsing 1 PhD student, and Bending and Schafer co-supervising a further 2 PhD students.