Large declines in UK farmland bird populations have become a major conservation issue. The UK Government now has a Public Service Agreement (PSA) to reverse these declines by 2020- Evidence for declines in farmland bird populations is strongest for arable-dominated regions of eastern and southern Britain, and until recently, most research into the causes of declines and remedial conservation management focused on arable systems
- Grassland accounts for 65% of agricultural land in Britain and there is growing evidence that a range of farmland birds have experienced serious population declines on pastoral farmland, especially in western regions of Britain. Seed-eating birds are those mainly affected, including buntings, finches & partridges
- The mechanisms driving these population declines are unknown, but probably include a loss of arable cultivation from many pastoral regions, the switch from hay to silage systems, and a consequent lack of seed and invertebrate prey
- Existing knowledge of farmland bird requirements suggests the introduction of low-input, spring-sown, cereal-based wholecrop silage (CBWCS) in an otherwise pasture-dominated landscape may have significant benefits for a range of farmland bird species, providing nesting sites during March-July, and feeding sites during summer and winter (on the following stubbles)
- Standard CBWCS usually involves high-input winter wheat, which provides limited nesting opportunities. Under-sown stubbles are also less attractive to seed-eating birds than conventional stubbles. The overall value to farmland birds is therefore probably limited.
To investigate the agronomic and biodiversity potential of cereal-based whole-crop silage (CBWCS) as a future agri-environment measure aimed at restoring farmland bird populations in pasture-dominated landscapes.What is Cereal-based whole crop silage (CBWCS)?
CBWCS is an alternative form of preserved forage that in recent years has become increasingly popular among livestock farmers. The cereal crop (usually wheat or barley) is harvested before the grain is fully ripe (40-45% dry matter or ‘soft cheddar’ stage), and fermented in silage clamps. CBWCS provides a feed of consistent quality and predictable dry matter yield, and increases milk yields in dairy cattle. Autumn-sown wheat is the most commonly grown CBWCS, but all cereals can be ensiled and spring-sown wheat, barley or oats are all possible alternatives. CBWCS can be undersown with grass and clovers, and bi-cropping with pulses or brassicas can be used to raise protein levels of the feed.
Methodology
At CAER, research efforts are focused on assessing the impact of the different forage crop systems on vegetation composition, vegetation structure and invertebrate assemblages at 16 farms located in Shropshire, Cheshire and Staffordshire. In particular, measurements will focus on quantifying the availability of food resources (seeds, invertebrates) for farmland birds.The forage systems to be investigated at each farm are winter wheat, spring barley, grass ley and maize (the latter two being experimental controls, representing the commonly used alternatives to CBWCS).
To compare conventional methods of barley production with guidelines provided by the Pilot Entry Level Scheme, the barley fields will be subjected to a split-field pesticide/herbicide regime in which standard whole crop cereal applications of herbicides will be applied to one half of the field and minimal inputs to the other.
The wheat and barley crops will be grown for two successive years on the same field. The first crop will be grown without undersowing and the second will be undersown with grass/clover, to allow re-entry into the grass rotation. .Data Collection
To assess the effect of year, eight of the eight sites will be adopted in the first year of study, and a further eight in year two. Arable plant (weed) and invertebrate densities will be assessed in a total of 16 wheat fields, 16 barley fields, 16 maize fields and 16 grass leys. Separate assessments will be made in the barley for the standard and reduced-herbicide regimes.
Assessments will be performed at distances of 2 m and 30 m from the crop edge along transects located within the Timed Watch Plot used for the bird observations by the RSPB. There are five TWPs for each farm, one in each of the maize, grass ley and winter wheat fields and one in each half on the spring barley fields.
Assessments of the arable plants (weeds) and invertebrates will be performed along each transect at 2 m and 30 metres from the field boundary. The arable plants are assessed in June, October and February, while invertebrate densities are assessed during the summer period.
Plant Data
To determine plant species composition depending on forage system, three 500 x 500 mm quadrats will be positioned 10 m apart perpendicular to the transect at 2 m & 30 m.For each quadrat, total percentage cover (non repetitive cover by vertical projection) is recorded for the crop, (maize, wheat & barley), graminoids, forbs, bare ground, bryophyte & litter cover (grass ley only).
Percentage cover (non repetitive cover by vertical projection) is then recorded for all vascular plant species. For each species, percentage cover is recorded separately for sexually reproductive plants, mature vegetative plants and seedlings.
Invertebrate Data
Vortis and sweep netting will be used to collect one sample from each of the distances (2 m & 30 m) along the transect.
Each vortis sample will comprise fifteen, 10 second sucks made by moving the Vortis vertically down on the vegetation. The catch from each set of 15 sucks being pooled. Samples will be evenly spaced out through an area 2 m x 15 m, with approximately 2 m between each position.
Each sweep net sample will comprise 30 sweeps taken at approximately 50 cm intervals in an area measuring 2 m x 15 m.
Policy Relevance
The study will provide an assessment of the costs, benefits and practicalities of CBWCS as a potential agri-environment measure aimed at livestock farmers.
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