Stability and resilience of fertilized grassland soils in response to extreme weather events

This project will be supervised by Dr Tancredi Caruso of Queen’s University School of Biological Sciences, Professor Paul Hallett of the University of Aberdeen’s School of Biological Sciences, and Dr Dario Fornara of the Agri-Food and Biosciences Institute The start date will be 1 October 2019.

The project explores the interaction between long-term nutrient fertilization and extreme droughts and floods on the stability and resilience of grassland soils. Extreme droughts and floods are already occurring more frequently with devastating effects in the UK and Ireland. Regional climate modelling predictions for Ireland suggest that by 2050, summers could have 20% less precipitation, while severe rainfall events could become more common in winter months.

The project is based on the hypothesis that the response of grasslands to more frequent, unpredictable and intense drought and flood will depend on management history and in particular on the long-term addition of inorganic and organic nutrients to soils. This project builds on an invaluable long-term grassland slurry experiment established by the Agri-Food and Biosciences Institute (AFBI) at Hillsborough in 1970. The experiment includes grassland plots that have never received nutrients (control plots) or have received either inorganic (NPK) or different types of organic (cattle vs. pig slurry) fertilizers for almost 50 years. Intact soil cores will be collected from these plots and subjected to different combinations of drought and flood to quantify how the management history of soil contributes to the response of key soil properties to extreme drought, flood, and their combination.

Specifically, the project aims to answer the following questions:
1) How do long-term inorganic vs. organic nutrient applications affect changes in the structure and resilience of the soil food web under drought, flood, and their combined effect?
2) How do the long-term inorganic vs. organic nutrient applications affect soil pore structure dynamics and organic matter decomposition rates under drought, flood, and their combined effect?

Future climate change scenarios pose a serious threat to the long-term sustainability of agricultural soils. The focus on the interaction between fertilization regimes and climate change dynamics will provide invaluable information to the future development of policy and management strategies for UK and Irish grasslands because it will help contextualise predictions on the negative impact of future extreme climatic events.

This project offers a unique opportunity for comprehensive training in the field of grassland management and soil ecology. Specifically, training will be provided in the formulation of field and glasshouse experimental design (AFBI, QUB), involving measurements of soil properties including food webs (QUB, AFBI), and soil physical behaviour and structural properties using state-of-the-art approaches such as XRay CT imaging (UoA). Data will be analysed with advanced statistical and dynamic modelling (QUB and UoA) to understand how grassland ecology responds to long-term nutrient management (AFBI).