Is mob grazing beneficial for soil health and the environment?

Alternative grassland management practices could improve productivity and help mitigate climate change. Grasslands play an important role in building soil fertility for sustainable development1 and the manipulation of grazing practices may increase soil carbon (C) sequestration through higher rhizodeposit-C and animal excreta inputs that have come about through improved soil fertility and more nutrient efficient plants.

Recently mob grazing grassland management has been increasingly promoted by farmers as a way of increasing soil health and C storage. There is, however, a lack of robust scientific evidence to support these claims, particularly in UK grassland systems. Mob grazing is "short duration, high density grazing with a longer than usual grass recovery period," where a large group of cattle are moved regularly and grass is left to recover for between 40 and 100 days2. Grasslands of different productivity tend to have distinctly different rates of soil C cycling and at appropriate intensity, grazing is thought to promote root growth which puts more C underground. Determining the potential of mob grazing for increasing soil health, C storage and predicting future changes requires knowledge of ecological responses and complex soil processes within grassland management systems.

Overall this project will use carefully selected grassland sites offering contrasting grazing management regimes on comparable soil types to assess productivity, soil health and C storage, nutrient cycling and ecological responses to mob grazing practices. It will explore the benefits that mob grazed vs traditional (set-stocked) grassland systems bring in terms of ecosystem services. Robust laboratory experiments using isotopic tracers will be designed to track C flow and investigate C cycling within contrasting grassland management systems. Interdisciplinary biological, chemical and physical techniques will be used to holistically assess soil health within contrasting grassland systems. Novel investigations will also test the application of 210Pb and 137Cs radioisotope techniques (indicators of grassland soil mixing and disturbance) alongside both non-destructive (e.g. plant ecology, in situ root and soil structure evaluation) and destructive (soil C, nutrient status, microbiology) assessments to increase our understanding of soil processes and C and nutrient storage within these systems.