Improving herbicide degradation studies: maintaining soil structure, microbial functioning and rhizosphere effects to reflect natural conditions

Aim: To develop a deeper understanding of the role of soil structure, the rhizosphere and microbial diversity on herbicide degradation rates, and to apply this knowledge to the design of test systems for use in predicting optimal application and environmental impact.
Objectives and approach
1. Quantify key physical and biological pathways and drivers of transformation of Crop Protection Products (CPP) in test systems and fields.
Under this objective, experiments will examine the effect of soil physical disturbance, soil type, and CPP chemistry on CPP biotransformation and the soil microbial (community size, composition, activity), biochemical (e.g. available carbon co-substrates) and biophysical characteristics (e.g. connected air and water ways; diffusion).
2. Develop methods which maintain or recreate key soil physical properties that retain functional diversity in soil microbial communities, so that degradation rates more closely reflect field measurements.
Building upon our experience in characterising soils with X-ray CT and recreating soil structure in microcosms, we will focus on identifying methods to control pore-solid interfaces and diffusive pathways.
3. to quantify the relative importance of the biophysical (soil structure), biochemical (rhizodeposition) and microbial (rhizosphere) effects on microbial communities brought about by the processes in the rhizosphere that contribute to driving differing CPP behaviour in planted versus non-planted soil.
Cover Crops will be grown in the Agri-Tech Soil Health Facilities to create realistic test systems (1 m3) each under controlled soil and environmental conditions. At an initial stage we test specific hypotheses using root surrogates to supply different sources of Carbon.