BD5208 Wide Scale Enhancement of Biodiversity (WEB) Final Report on Phase 2, and Overview of Whole Project Executive Summary
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BD5208 Wide Scale Enhancement of Biodiversity (WEB) Final report on phase 2, and overview of whole project Executive summary Core objective The WEB project aimed to inform the development of new or existing Entry Level (ELS) and Higher Level Stewardship scheme (HLS) options that create grassland of modest biodiversity value, and deliver environmental ecosystem services, on large areas of land with little or no potential for creation or restoration of BAP Priority Habitat grassland. Specific objectives Quantify the success of establishing a limited number of plant species into seedbeds (ELS/HLS creation option) and existing grassland (currently HLS restoration option) to provide pollen, nectar, seed, and/or spatial and structural heterogeneity. Quantify the effects of grassland creation and sward restoration on faunal diversity/abundance, forage production and quality, soil properties and nutrient losses. Develop grazing and cutting management practices to enhance biodiversity, minimise pollution and benefit agronomic performance. Liaise with Natural England to produce specifications for new or modified ES options, and detailed guidance for their successful management. Overview of experiment: The vast majority of lowland grasslands in the UK have been agriculturally improved, receiving inputs of inorganic fertiliser, reseeding, improved drainage and are managed with intensive cutting and grazing regimes. While this has increased livestock productivity it has led to grasslands that are species-poor in both native plants and invertebrates. To rectify this simple Entry Level Stewardship scheme options have been developed that reduce fertiliser inputs; this includes the EK2 and EK3 options. While permanent grasslands receiving low fertiliser inputs account for the largest area of lowland managed under the agri-environment schemes they currently provide only minimal benefits for biodiversity or ecosystem services. In addition, such low input grasslands have low value for livestock production. Developing new multi-functional seed mixtures and understanding how they can be managed to enhance biodiversity, ecosystem service delivery, 1 soil structure and nutrient value while simultaneously supporting a commercially attractive level of livestock production is a missing link in the toolbox of Entry Level Stewardship grassland options. This Wide Scale Enhancement of Biodiversity project aims to address these issues. In 2008 a multi-factorial experiment was established to develop simple, low cost (seed cost ≤ £230 ha-1) options that both enhance biodiversity and ecosystem services, including crop pollination and soil structure. We established three seed mixtures differing in the key groups of plants they contained (‘grass’ only (G), ‘grass & legume’ (GL), and ‘grass, legume & forb’ (GLF)), and investigated management practices involved in their establishment and long term maintenance. These included seed bed preparation (‘minimal tillage cultivation’ vs ‘conventional deep ploughing’), the type of sward management (cut vs grazed) and intensity with which that management is applied (typical continuous management vs a summer rested period). The study was undertaken on two experimental grasslands, one in Devon (North Wyke) and one in Berkshire (Jealott’s Hill). These grasslands had previously been agriculturally improved, having been both reseeded as well as receiving regular application of inorganic fertiliser to maximise livestock productivity. North Wyke was last ploughed and reseeded with perennial ryegrass and white clover in 1998. Jeallot’s Hill was previously under arable cultivation in 2004. Although both were floristically species poor (less than 3 species m-2) underlying soil conditions contrasted significantly, with one site on poorly structured compacted London clay (Jealott’s Hill) and the other on brownish clay loams sitting over impermeable clay (North Wyke). Direct monitoring of these experimental sites occurred over four years from 2009 to 2012 following their sowing in 2008. In this executive summary we highlight our principal findings in terms of how our experimental treatments influenced: 1) The establishment of ecological generalist legume and non-legume forb species into high fertility grassland following conventional or minimal cultivation; 2) sward and livestock productivity; 3) persistence of sown plants over the five years once established into the grasslands; 4) soil parameters, including nutrient loading and soil compaction; 5) water leachate quality as an indicator of diffuse pollution risks; and 6) food web enhancement focusing on insect pollinators and the provision of feeding resources for farmland birds. Summary tables are given after the text. The establishment of generalist legume and non-legume forbs The utility of any seed mixture in delivering increased sward productivity, biodiversity or promoting aspects of soil structure and nutrient retention is ultimately dependent on its capacity to establish effectively into nutrient enriched competitive ex-improved grassland swards. This question was addressed in Phase 1 of the study (2008-2010). At North Wyke ploughing and conventional seed bed preparation was the most successful cultivation practice. At Jealott’s Hill the benefits of ploughing over shallow cultivation were equivocal. The results of this study indicate that for shallow cultivation to be successful in allowing high establishment of sown legume and non-legume forb species severe reduction in competition by the existing/original sward constituents is required. At Jealott’s Hill the shallow cultivation technique completely disturbed the existing sward and created more than 80 percent bare ground, whereas at North Wyke the shallow cultivation technique disturbed 40 - 50 percent of the existing sward creating 40-50 percent bare ground. It is probable that if herbicide had 2 been used in conjunction with the shallow cultivation at North Wyke competition by the existing sward would have been controlled and shallow cultivation may have resulted in establishment success comparable to the ploughed treatment. Productivity Farmer’s uptake and perception of the value of these seed mixtures will depend to a large extent on their capacity to support livestock, as measured by biomass production and forage quality. Understanding the extent to which different seed mixtures are able to compensate for the loss of inorganic fertiliser inputs is therefore valuable when evaluating the utility of these swards as ELS or HLS options. At North Wyke the dry matter yields of cut silage and the animal stocking rate that the established grasslands were able to support were greatest within the unfertilised more diverse seed mixtures, that is the ‘grass & legume’ (GL) and ‘grass, legume & forb’ (GLF). Although stocking rates were not investigated at Jealott’s Hill, these same diverse seed mixes were found to support higher dry matter yields from the cut silage. Peak dry matter yield from the GL and GLF sward were typically in the range of 6 – 8 tonnes ha-1, although over time the loss of agricultural cultivars of legumes from the sward meant that by 2012 this had been reduced to c. 3 tonnes ha-1 at one site (Jealott’s Hill). This increased yield, at least initially, was directly linked to the establishment of nitrogen fixing legumes within the GL and GLF swards. For example at Jealott’s Hill dry matter yield was c. 5-6 tonnes ha-1 higher in the GLF plots relative to swards established using the ‘grass’ only (G) seed mixture. Although sward productivity was generally higher at North Wyke, poorer establishment and persistence of legumes meant that the difference in dry matter yields between the G and the more diverse GL and GLF seed mixtures was smaller, typically between 1-3 tonnes ha- 1. Where initial seed bed cultivation in 2008 was achieved using minimum tillage, as opposed to more conventional deep ploughing approaches, there was also an indication that silage cuts produced greater dry matter yields, although typically by a small amount of no more than 1 tonne ha-1 for the more productive GLF seed mixes. The nutritional quality of the forage for livestock was also superior where legumes were included as part of the establishing seed mixtures. Sward nutritional value was higher in the GL and GLF plots where legumes were sown, although at North Wyke non-legume forbs further increased forage quality in the GLF seed mixture. Even though this was not seen at Jealott’s Hill there was evidence that the rate of decline in herbage nutritional quality over time could be reduced where non-legume forbs were also part of the sown seed mixture. In general though this improved nutritional value reflects the key role played by nitrogen fixing legumes, and was most apparent in the higher nitrogen concentrations of forage in the GL and GLF silage. At least at North Wyke, deeper-rooting forb species may have been able to access micronutrients within the soil matrix leading to the increased mineral content for the GLF seed mixtures at this site. As agricultural cultivars of legumes did not persist throughout the entire five year period there tended to be a reduction in the nutritional value of forage over time, for example at Jealott’s Hill forage quality in terms of the content of nitrogen, phosphorus and potassium fell over the five years. Shallow minimum tillage cultivation used to create the seed bed in 2008 increased the nitrogen content of the sward at Jealott’s Hill, although this effect was small. At North Wyke there was also