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Characterisation of soil structural degradation under grassland and development of measures to ameliorate its impact on biodiversity and other soil functions. - BD5001

Defra have identified compaction in grasslands as an important issue that may threaten the achievement of agri-environment scheme objectives in England and Wales. There is, therefore, a need to improve our understanding of soil compaction in grasslands and to identify and evaluate mitigation methods that will enhance the ability of agri-environment schemes to meet their objectives.

In the first part of this project, we will carry out a NATIONAL SURVEY of soil compaction in grasslands. We will identify and visit 300 grassland fields covering improved, semi-improved and unimproved grassland pastures and hay meadows; fields within and without agri-environment schemes (including arable reversion to grassland); and a range of soil types across the main grassland areas of England and Wales. Each field will be characterised in terms of the grassland type and management system (e.g. livestock type and number, grazing and cutting frequency), whether it is part of an agri-environment scheme, the landscape unit, the soil type, and the presence and nature of soil compaction. Soil compaction will be quantified by a combination of visual soil assessment (including the presence of wheeling ruts, poaching etc.) and the use of soil bulk density, cone penetrometer and shear vane measurements. At 30 of the most compacted sits, we will also assess the presence of subsoil compaction. We also propose to characterise the sites in relation to measured topsoil clay and organic matter contents, which are known to be key factors controlling soil bulk density and compaction.The resulting data will be stored in a Microsoft Access database and will provide an indication of how types of grassland soil compaction link across to grassland management systems both within and outside agri-environment schemes. Also, the topsoil samples will be stored in the soil archive at ADAS Gleadthorpe, should they be required for further analysis/reference purposes.

The second part of the project will identify practical soil compaction MITIGATION METHODS, focusing on mechanical soil loosening and the introduction of plant species with compaction alleviation properties. We will then set up four large plot-scale experiments across England and Wales to investigate the impact of the selected soil compaction alleviation methods on plant communities, water infiltration rates, invertebrate numbers, bird foraging behaviour, soil microbial activity, organic carbon storage, nitrous oxide emissions and soil compaction itself. The analysis will include an assessment of treatment effects on grassland productivity and vegetation palatability.

Finally, we will also use split fields to investigate the impact of soil loosening on the preference of FORAGING BIRDS for probing. Using established techniques, previously used to determine bird preferences for short or long swards, we will establish 15 sites to observe wild bird behaviour and distribution between loosened and compacted parts of fields.

The overall analysis will identify mitigation methods with potential to ALLEVIATE SOIL COMPACTION and have a positive impact on soil functions (e.g. water infiltration rates, nitrous oxide emissions) and biodiversity. The findings will be summarised in an interim report on the national grassland characterisation survey and a final report on the plot- and field-scale experiments, including an assessment of the ecological processes/mechanisms involved. The final report will include text, images and technical information that could underpin the production of a Technical Advice Note on soil compaction and loosening and the establishment of grassland plant communities.

In addition, results will be communicated through regionally based soil workshops for advisers and land managers via visits to the four experimental platform sites.
The main objective in this project is to:

1) Better understand the nature of soil structural degradation in enclosed grasslands and to identify and evaluate physical (including mechanical) and biological measures that may be used to alleviate its negative impacts on soil functions, including biodiversity.

To achieve the overall project objective, there are a number of specific research objectives, viz:

3.1 Characterise soil structural degradation in grassland fields in England and Wales.
Activity: Survey a total of 300 grassland fields across England and Wales covering both grazed fields and fields under a silage or hay regime. Characterise the fields according to the specific grassland type, management system and soil type and carry out soil penetrometer, shear vane and bulk density measurements; and visual soil assessments to determine the nature of soil compaction (months 2-9).

Output: Characterisation of grassland soil compaction according to soil type, grassland type and management system across a wide range of sites in England and Wales.

3.2 Identify measures which could be incorporated into agri-environment schemes in England and Wales.
Activity: Carry out a detailed literature search to obtain a comprehensive list of candidate plant species to introduce to grasslands to alleviate compaction (months 1-5). Agree with Defra a short list of mitigation methods (both biological and mechanical) to apply to a selection of grassland fields that represent ‘typical’ grassland farming systems in England and Wales (months 1-12).

Output: Field studies to investigate the impact of soil compaction mitigation methods (both biological and mechanical) on soil productivity, biodiversity, water infiltration and nitrous oxide emissions.

3.3 Evaluate methods (see later), which could be incorporated into agri-environment schemes in England and Wales. Assess the impact of soil compaction and treatments on:
o soil structure/soil compaction
o soil carbon storage
o soil water infiltration rates
o vegetation composition (ability to restore grassland plant communities)
o vegetation palatability
o invertebrates and soil biota (microbial communities)
o bird foraging
o biomass production
o nitrous oxide emissions

Project Documents
• FRP - Final Report : BD5001 Literature Review of the Use of Plant Species for Remediation of Soil Compaction   (343k)
• FRP - Final Report : BD5001 The alleviation of grassland compaction by mechanical soil loosening_Final Report   (370k)
• FRP - Final Report : BD5001 WP1 Final report   (4192k)
• FRP - Final Report : BD5001 WP1 FINAL REPORT May 2012   (1898k)
• FRP - Final Report : BD5001 WP3 Final Report   (3358k)
• SPE - Specification : CTE0822 specification   (48k)
Time-Scale and Cost
From: 2009

To: 2014

Cost: £784,975
Contractor / Funded Organisations
Environmental Protection              
Habitat conservation              
Nature conservation