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A project to examine the use of lenient grazing on agricultural grassland to promote in-field structural heterogeneity, invertebrates and bird foraging (extension of BD5206) - BD5207

Description
This study aims to develop and test reduced intensity grazing options for agricultural grassland that aim to deliver substantial benefits for biodiversity (particularly invertebrates for foraging farmland birds) that are simple, practical and low cost for farmers to implement. This evidence will inform grassland management options within agri-environment schemes in order to ensure they contribute to scheme objectives and biodiversity targets. Evidence to inform the enhancement of swards to support farmland bird species is a key focus of this project.

A lack of a suitable range of invertebrate prey has been shown to limit the breeding success of a range of priority farmland birds in Britain. The study will test two lenient cattle grazing treatments both of which should be widely applicable to livestock farmers across the UK. Grazing grassland more leniently leaves more vegetation in situ for longer and this allows a range of invertebrates to develop and reproduce. However, a tall dense sward can inhibit some invertebrate groups (that need warmth from sunlight or bare ground for laying eggs) and can prevent birds accessing invertebrate prey. A reduced density of livestock encourages cattle to graze selectively and thereby generate a sward with a fine-scale mixture of tall and short patches of vegetation that should maximise benefits for invertebrates and foraging birds. The aim of this project is to create structurally diverse swards that promote invertebrate prey abundance and provide access for birds to those prey.

Previous work (BD1454) tested lenient grazing couple with early cessation of grazing. Although this had a large positive impact on invertebrate abundance, the swards were too tall and dense to promote bird foraging and costs to farmers were relatively high. The grazing treatments being tested in this study have been developed to meet the sward requirements of priority farmland birds (like yellowhammers and cirl buntings) while minimising costs and complexity for farmers. Grazing grassland less intensively should confer a range of wider environmental benefits including reduced fertilizer inputs, improved soil structure, reduced soil erosion and run-off, enhanced pollinator services and increased resilience of biodiversity to climate change impacts.

The two lenient grazing treatments proposed in this study were successfully established on six sites in South Devon during 2010. Despite initial problems with treatment establishment caused by a prolonged period of dry weather and evidence of carry-over effects from the previous work, initial findings were encouraging. Leneint grazing substantially increased sward structural heterogenity, the abundance of invertebrates important in the diets of farmland birds (by 50%), and plot usage by skylarks (four times greater usage) and buntings (five time greater usage). The agronmic costs of both lenient grazing treatments were modest in 2010.
Objective
1. To assess the biodiversity benefits and agronomic costs of continuous and intermittent lenient cattle grazing of agricultural grassland, and specifically to assess:

(a) the effects of lenient grazing on fine-scale structural sward heterogeneity,

(b) the effects of lenient grazing and the subsequent changes in sward structure on invertebrate abundance and community structure,

(c) the responses of foraging birds to changes in sward structure and invertebrate communities.

2. To recommend lenient grazing options suitable for inclusion in Natural England’s Entry Level or Higher Level agri-environment Schemes.
Project Documents
• FRP - Final Report : SID5 BD5207 final report   (689k)
• TPS - Two Page Summary : BD5207 2pg sum   (304k)
Time-Scale and Cost
From: 2011

To: 2013

Cost: £294,045
Contractor / Funded Organisations
ADAS UK Ltd., Royal Society for Protection of Birds, CABI Bioscience
Keywords
Environmental Stewardship