Temporary grassland leys and agricultural soil health

Grasslands are found across most biomes globally, and have been manipulated by humans for
millennia. Under modern management, mainly for grazing livestock, grasslands can be established
for as little as 1-5 years. They are subject to a variety of inputs, grazing pressures, cover crop species,
and durations of establishment. Because of the scale of grassland land cover globally, they are a
potential resource for tackling three challenges centred around carbon: soil health, climate change,
and food production. Soil carbon is essential for soil health and maintaining the capacity for
sustainable harvest, but carbon has been lost from soil to the atmosphere.

Using in situ and ex situ experiments, and a meta-analysis, we investigate interactions between
different cover crop species and their effect on carbon, both total and in pools of recalcitrance,
across scales of time and depth. We investigate the potential for short-term leys to improve
agricultural soil health by incorporating carbon from the atmosphere, and the processes by which
carbon might be transferred back to the soil. There is a focus on depth, to explore the potential for
leys to store carbon away from atmospheric and environmental interference, and on time, due to
the short-lived nature of grassland leys. Grazing is explored as a potential tool for grassland
management for soil emissions reduction.

This work investigates the potential for storing carbon, in fractions of recalcitrance, across depth
profiles of soil under temporary grassland leys. Experiments over 1-2 years show time progression of
carbon reactivity and how plant species influence total carbon in soil with different management
strategies. This thesis demonstrates the complexity of interactions in processes that affect soil
carbon, and suggests new avenues for future research into these processes.