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Botanical Assessment of Sown Grass Margins in the Countryside Stewardship Scheme C N R Critchley, J A Fowbert & A J Sherwood1 Final Report June 2005 ADAS Redesdale, Rochester, Otterburn, Newcastle upon Tyne NE19 1SB, UK 1ADAS Boxworth, Boxworth, Cambridge CB3 8NN, UK MA01017 CSS Grass Margins ADAS June 2005 CONTENTS Summary......................................................................................................................... 4 Introduction...................................................................................................................... 6 Methods........................................................................................................................... 7 CSS prescriptions........................................................................................................ 7 Site selection ............................................................................................................... 7 Field survey................................................................................................................. 7 Data analysis............................................................................................................... 8 Results ...........................................................................................................................10 All margin types ..........................................................................................................10 Sown grass margins ...................................................................................................16 Sown margins and environmental variables ................................................................19 Older sown margins and environmental variables .......................................................20 Rare species...............................................................................................................22 Discussion ......................................................................................................................23 Vegetation establishment............................................................................................23 Vegetation development .............................................................................................23 Variation in species composition .................................................................................23 Rare arable plants ......................................................................................................24 Methodological issues.................................................................................................24 Conclusions................................................................................................................25 Recommendations......................................................................................................25 Acknowledgements.........................................................................................................26 References .....................................................................................................................27 Appendices.....................................................................................................................31 3 MA01017 CSS Grass Margins ADAS June 2005 Summary 1. Field boundaries are important linear features in arable landscapes. The perennial grass or herbaceous verge next to the crop is beneficial to biodiversity and serves other functions but verges have been damaged and reduced in extent by intensive agricultural practices. To counteract this, the Countryside Stewardship Scheme (CSS) has encouraged farmers in England since 1993 to establish 6 m grass margins (management option ‘R3’) using either a limited selection of grass species or, more recently, a diverse seed mixture including perennial forbs. The CSS has made a substantial contribution to exceeding area targets set under the UK Biodiversity Action Plan for cereal field margins. 2. Most previous research on the establishment of grass margins has been short-term or applied at a limited number of sites, so the outcome of establishing grass margins at a national scale and over longer timescales was uncertain. The aim of this study was to assess the plant species composition of grass margins established in the CSS. 3. Four types of field margin were surveyed in 2004. These were grass margins sown with a simple grass seed mixture before 2002 (R3 pre-2002) or more recently (R3 post-2001), margins sown with a more diverse seed mixture including perennial grassland forbs (R3 + F) and normally cropped cereal headlands (controls). In total, a stratified random sample of 119 sites from eight Defra administrative regions was surveyed. At each site, botanical data were collected from 30 randomly located quadrats, soil cores were collected and the site searched for rare arable plant species. Data on management practices and habitat context were collected for each site. Data were analysed using ordination methods, Analysis of Variance and variation partitioning by Partial Redundancy Analysis. 4. In total, 264 taxa were recorded. Grass margins were markedly different from the control sites, which, apart from the obvious presence of the cereal crop and absence of other sown species, had lower abundance of grasses, forbs, perennials and butterfly larva and bumblebee foodplants. A small number of grass margins had been established by natural regeneration and tended to have more weedy perennials or annual arable species. The most abundant species at sown margins were the grasses included in the seed mixture. 5. A comparison of sown margins showed that R3 + F sites had higher species richness and numbers of sown species and perennial forbs than margins without additional forbs in the seed mixture. Forbs characteristic of grassland were only present at very low frequency in R3 pre-2002 and R3 post-2001 sites but, in contrast, were relatively common in R3 + F sites. Invasive, competitive perennials were, however, frequent at all sown sites. Annuals were more abundant in R3 post-2001 sites than older sown sites. 6. Most (85%) sown grass margin sites had loamy soil. Arable, woodland and grassland were the most common adjacent land uses and hedges, broadleaved trees and grass/tall herb verges the most common field boundary features. Two-thirds of sites over two years old were cut annually and more than half had cuttings removed. 7. The addition of forbs to the seed mixture had a significant effect on species composition of sown grass margins. Regions, soil extractable K, soil texture and age of site were also related to species composition. In sown margins older than two years, species composition was related to additional forbs in the seed mixture, regions, soil K and pH but not to age of margin. Region, soil properties and the addition of forbs tended to have independent (non-overlapping) effects on species composition. Species composition was not related to site management, adjacent land use, field boundary, slope, aspect or altitude. 8. No rare annual, arable plant species were found in CSS margins but there was one record of Apera spica-venti (loose silky-bent) at a control site. 9. In general, margins sown with simple grass seed mixtures were established successfully. Perennial grassland forbs only colonised at very low frequencies but did tend to establish and persist when included in the seed mixture. Therefore, their inclusion should be encouraged to enhance botanical diversity and foraging 4 MA01017 CSS Grass Margins ADAS June 2005 opportunities for nectar and pollen feeding invertebrates. The current mowing regimes are appropriate although more active management could be promoted to encourage further colonisation and spread of perennial grassland forbs. Grass margins should not be sited where annual plants are a priority for conservation. 5 MA01017 CSS Grass Margins ADAS June 2005 Introduction Field boundaries are important linear habitats in lowland arable farmland landscapes. The boundary usually comprises a hedge, trees, ditch, bank or other semi-natural feature but can also include a perennial grass or herbaceous verge next to the crop. The verge serves many functions potentially, including provision of valuable habitat for flora and fauna and a buffer zone that protects the remainder of the boundary from fertiliser and pesticides applied to the crop (Marshall & Moonen, 2002; Meek et al., 2002). The perennial vegetation also prevents annual weeds from establishing in the boundary and spreading to the crop (Smith et al., 1999b; Moonen & Marshall, 2001). However, in the UK and Western Europe, many field boundaries have been removed as field sizes increased to accommodate modern farm machinery. In those remaining, the verge has often been lost or reduced in extent by mechanical cultivation close to the main field boundary feature. Contamination of verges by fertiliser and pesticides has also reduced their plant species diversity. To counteract these losses, research has focussed on methods of re-establishing perennial margins between the remaining field boundary and the crop. Experiments have shown that sown grass species can establish successfully. Species that form a dense, tussocky sward are advocated to provide habitat for invertebrates and other fauna (Thomas et al., 1991; Collins et al., 2003). Annual species are usually suppressed after the first year (Smith & Macdonald, 1989; Kirkham et al., 1999; Huusela-Veistola & Vasarainen,