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Sustainable nutrient management of semi-natural neutral grasslands - BD1468

This project is designed to provide scientific underpinning of refinements to existing UK agri-environment (AE) fertilizer and liming prescriptions for the maintenance of species-rich semi-natural grassland (AE option HK6). The specific aim is to define sustainable fertilizer practices for lowland and upland meadows, which are UK Biodiversity Action Plan (BAP) priority habitats. The project will examine whether inorganic fertilizer can be used as an alternative to the traditional practice of using farmyard manure (FYM) on species-rich grassland and quantify the consequences for plant diversity of variation from sustainable fertilizer practice. FYM is now a scarce resource in much of the grassland dominated agricultural landscapes of the UK, particularly in Wales. Therefore, the identification of sustainable alternatives to FYM is urgently needed to inform AE policy and option prescriptions for these scarce biodiversity rich resources. The project is also designed to define fertilizer practices that would allow high diversity to become established on species-poor meadows. This information is needed to underpin the management agreements for the restoration of species-rich grassland (AE option HK7). The agronomic value in terms of yield and nutrient content of herbage obtained from species-rich meadows will be quantified at the time of cutting for hay. Relationships between the botanical responses to different fertilizer practices and long-term changes in soil chemistry and soil microbial community will be examined. Changes in soil microbial communities and the nutrient mineralisation processes that they control can be slow to emerge. However, the long-term maintenance of species-rich grassland will be dependent upon maintaining the soil chemistry and microbial community within prescribed ranges, which we need to identify. The value of the soil microbial community as an indicator of a site’s restorability potential from species-poor to species-rich grassland will also be examined.

This project is based on the experiment that was established in BD1415 and continued as BD1456. The experimental sites were a lowland unimproved and an adjacent semi-improved neutral meadow in south east Wales and an upland unimproved and near-by semi-improved neutral meadow in Cumbria. All of the fertilizer treatments initiated in 1999 in BD1415 have been continued since. All fertilizer treatment plots were limed in 2005 to ensure that botanical and agronomic responses to the different treatments were associated with neutral (pH 6.0) soil conditions. Prior to liming the soil pH was in the range 4.9-5.8 across the study sites. Liming effects on soil base status can take between one and two years to fully develop. The botanical, soil microbial and agronomic responses to the combination of fertilizer inputs and enhanced base status would, therefore, have been at an early stage of development at the end of BD1456, in 2007. Monitoring the treatment plots over a further three years should ensure that the above and below ground community responses have had time to develop more fully.

To date BD1415/1456 has provided clear evidence that the ecological value of unimproved meadows is likely to be damaged by annual applications of 24 t FYM /ha. However, questions still remain over the sustainability of the annual 12 t FYM /ha treatments and the effects of annual vs. periodic applications of 12 and 24 t FYM /ha. In BD1415 inorganic NPK applications predicted to be equivalent to annual applications of 12 or 24 t FYM /ha had not damaged the ecological value of the study meadows to the same extent as their respective FYM treatments. During the course of BD1415, it emerged that the supply of plant available N and P in the FYM may have been underestimated. The amounts of N and P supplied as inorganic fertilizer in the “equivalent” treatments were, therefore, considered to have been too low. Consequently the amounts of plant available N and P as percentages of the total in the FYM were increased from 10 to 12% and from 60 to 80 %, respectively, from 2007 onwards. Elevated P supply, in particular, is known to have a negative effect on grassland plant diversity. Therefore any effects of the changes to the inorganic treatments in 2007 needs to be monitored for at least three more years to provide evidence that the inorganic fertilizer treatments are in fact sustainable in terms of plant diversity maintenance. The soil microbial community response to the different fertilizer treatments should also provide evidence of unsustainability of particular fertilizer practices for the meadow ecosystem.

Low yields of late cut hay of low feed value for productive ruminant livestock from unimproved meadows make the management of such meadows unattractive to farmers. Evidence is emerging from BD1415/BD1456 of negative relationships between meadow productivity and species-richness and between yield predictability and species-richness. The proposed project will examine these relationships under the treatment refinements that occurred in 2005 and 2007 to define the productivity range of unimproved meadows under sustainable fertilizer practice.

The overall aims of the FYM 3 project are to define nutrient management practices to maintain existing high botanical diversity or allow high diversity to be restored on impoverished neutral meadow communities.

Specific objectives
1.1 Establish sustainable nutrient management practices that maintain or enhance the botanical interests of representative unimproved or semi improved ‘neutral’ meadows.

1.2 Quantify effects on botanical composition and functional character of representative unimproved or semi improved ‘neutral’ meadows of incremental deviations from sustainable nutrient inputs.

1.3 Establish whether the use of FYM or inorganic fertilizer supplying predicted equivalent amounts of NPK have different effects on botanical composition of representative unimproved or semi improved ‘neutral’ meadows.

1.4 Establish liming practice that maintains or enhances the botanical interests of representative unimproved or semi improved ‘neutral’ meadows.

2.1 Establish whether nutrient management practices that have maintained or enhanced the botanical interests of unimproved or semi improved ‘neutral’ meadows have also maintained soil microbial communities typical of such meadows.
2. 2 Establish whether the use of FYM or inorganic fertilizer supplying predicted equivalent amounts of NPK have had different effects on the soil microbial communities of representative unimproved or semi improved ‘neutral’ meadows.
2.3 Examine differences in time scale of treatment effects on the botanical and soil microbial communities
2.4 Examine the value of soil microbial community composition as an indicator of restoration potential for high nature value meadow communities
3. Quantify the productivity of neutral meadows under sustainable nutrient management practices that have maintained or enhanced botanical interests
4. Examine the effect of sward enhancement (seed addition) on the restoration of species poor semi-improved grasslands

5. Produce a guidance document detailing the use of organic pelleted manure and its effect on soil, herbage production and ecological variables.
Project Documents
• FRP - Final Report : BD1468 sid5 am vs 22 Feb 2012   (251k)
• ANX - Annex : BD1468 Appendix 1, Kirkham et al Botanical paper 1   (893k)
• ANX - Annex : BD1468 Appendix 2, Kirkham et al Botanical Paper 2   (811k)
Time-Scale and Cost
From: 2008

To: 2011

Cost: £478,794
Contractor / Funded Organisations
North Wyke Research, ADAS UK Ltd.
Environmental Protection