Individual study: Diversifying upland meadow flora through cutting and grazing at Colt Park, North Yorkshire, England
Smith R. & Corkhill P. (2000) Diversifying upland meadows. Enact, 18-21
Meadows at Colt Park in Yorkshire (northern England), were of little conservation interest due to past agricultural improvement, including the application of mineral fertilisers. Various cutting and grazing regimes were initiated to see if the grassland could be restored to herb-rich meadows.
An experiment was set up in 1989 in one of the meadows at Colt Park. Treatments were chosen to mimic:
1) a traditional management regime i.e. no mineral fertilization, 21 July hay-cut, autumn grazing with cattle and spring grazing with sheep;
2) a modern variant i.e. 14 June cut;
3) aspects of the Pennine Dales Environmentally Sensitive Area (ESA) management prescription i.e. small additions of mineral fertiliser;
4) an historical variant i.e. 1 September cut.
Grazing treatments were undertaken in nine paddocks, with three replicates of each of three treatments:
1) autumn cattle grazing plus winter and spring sheep grazing;
2) winter and spring sheep grazing;
3) autumn cattle grazing.
Each paddock was divided into three strips each cut for hay on 14 June, 21 July and 1 September. Each strip was sub-divided in two, one half being unfertilised, the other treated with a proprietary 20:10:10 NPK brand (25 kg/ha nitrogen (N), 12.5 kg/ha phosphorus (P) and potassium (K)), spread by hand in early May each year.
Each fertilised plot was subdivided into two for a seed addition treatment in one subdivision. Some seed was collected locally. Seed of 19 species was bought from a commercial source. Seed was sown by hand in autumn 1990, 1991 and 1992. Plant species diversity and hay yields were monitored utnil 1998.
Plant species diversity: Diversity did not change significantly until 1996. Subsequently, more species were recorded on the unfertilised plots where the sward was cut on 21 July, where grazing occurred in both autumn and spring, and where seed was sown (16 to 24 species in 4 m²). Conversely, there was a 25% reduction in diversity (to 14 species) in plots ungrazed by cattle in autumn, cut on 14 June and with no seed added. Many sown species appeared in unfertilised plots cut in June and July, grazed in autumn and spring. Some species disappeared, occasionally reappearing over the eight years. Three of the most interesting (scarce species) were oval sedge Carex ovalis, downy oat-grass Avenula pubescens and twayblade Listera ovata. These appeared in 1998, perhaps indicating colonisation from adjacent habitats.
Hay yield: Lowest hay yields were found with autumn and spring grazing (4-5 tonnes/ha), hay cut on 14 June (2-3.5 tonnes/ha) and absence of mineral fertiliser (4-6 tonnes/ha). Highest yields were obtained in fertilised plots cut on 1 September. High yields were also associated with low plant species diversity. Yields generally declined over time.
Establishment of yellow rattle: Yellow rattle Rhinanthus minor was one of the sown species. The 1996 increase in species diversity coincided with increased yellow rattle density (more than 40 plants/m²), particularly marked in traditionally managed plots. Yellow rattle is a hemi-parasite of many meadow species, particularly competitive grasses. The experiment may have been successful in part as yellow rattle reduced grass competition thus facilitated increases in herb diversity.
Conclusions: The importance of traditional grazing practices only became evident after eight years. Soil throughout the experiment had a high residual fertility (18 mg/l P) which may have been a factor delaying increases in species diversity.
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