Management for Biodiversity in Grassland Farming Systems

Keywords: Biodiversity, Stocking densities, Sward structural diversity, Species diversity, Grazing management.

Grassland intensification, largely since World War Two has been responsible for a substantial decline in biodiversity on farms. Increases in stocking density, forage conservation practices and fertiliser application have been the main causal agents.

One component of agri-environment support measures throughout Western Europe is the encouragement of biodiversity in grassland farming systems. The effects of grassland management practices of grazing, cutting and fertilisation on aspects of biodiversity are considered. In the absence of sufficient propagules for recolonisation, physical aspects of recreation of species diverse pastures are reviewed as well as those practices which impinge on biodiversity in field margins.

Grazing can be used to manipulate sward composition and associated biodiversity but the results are inconclusive, often unpredictable and dependent on features beyond the sward itself. Structural diversity of grazed swards is of some consequence for a wider range of biodiversity than plant species diversity. The application of inorganic fertiliser is largely antagonistic to plant biodiversity, however, effects on other wildlife are less clear. To achieve biodiverse grasslands, soil potassium (K) levels are unimportant, soil phosphorus (P) is the key element, probably interacting with nitrogen (N) and the application of lime on biodiversity should be further investigated. Soil P levels must be reduced below 5-8 mg P/100g (acetate extraction) and physical enhancement of biodiversity is only likely to be successful if the top layer of soil is removed, reducing soil organic matter and phosphate status. It is the contention of the authors that in the future, the use of herbicides will not be permitted, fertiliser application will become more restricted, particularly in relation to agri-environment schemes and good farming practice and it is likely that the only opportunity left to manage grasslands for biodiversity will be variations in grazing management with possible lime and manure applications. In this context experiences in varying grazing directly from another grassland area which has a shorter history of stocking and lower stocking densities (the Falkland Islands) can provide useful pointers for the future.

The authors conclude that biodiversity in grassland farming systems can be maintained and even enhanced through a co-ordinated and long-term approach at the whole farm system level. This requires schemes to adopt management practices that recognise environmental objectives and marry these to the requirement of maintaining a potentially profitable farming system.

James H McAdam, Department of Agricultural and Rural Development, Belfast and Queen’s University Belfast, N. Ireland, UK.

J Aidan Kerr, Department of Agriculture, Falkland Islands Government, Stanley, Falkland Islands.

George E J Fisher, Kemira Agro UK Ltd, Chester, UK.

Jerry R B Tallowin, Institute of Grassland and Environmental Research, North Wyke, UK.

27 Pages, 1 Figure, 2 Tables, 75 Refs.