Individual study: Management of grass pastures for brent geese Branta bernicula at Old Hall Marshes RSPB Reserve, Essex, England
Vickery J.A., Sutherland W.J. & Lane S.J. (1994) The management of grass pastures for brent geese. Journal of Applied Ecology, 31, 283-290
In parts of the UK, increasing numbers of brent geese Branta bernicula feed inland where they damage arable crops. However, there is little agricultural conflict when they graze on grass pasture and encouraging geese onto pasture is a way of reducing conflict with farmers. Over a 2-year period the grazing intensity of wintering brent geese was monitored on areas of grass pasture managed experimentally under different cutting, grazing and fertilizer regimes.
Study site: The experiment was conducted at Old Hall Marshes RSPB Nature Reserve. The c. 20 ha field used was put down to grass in 1983 and subsequently managed since 1985 by sheep grazing and cutting for hay or silage.
Treatments: A random block design experiment was set up in March 1990, comprising 18, 100 x 75 m plots with six replicates of each of three treatments (with and without fertilizer application):
1) Cut - cut for silage on 26 June and cut once with a rotary cutter in late August;
2) Cut and aftermath grazed - cut for silage on 26 June and grazed from 26 July to 20 August with seven ewes and lambs at foot in each plot (equivalent to 29.12 Livestock Unit Days (LUD)/ha over 26 days), and from 4 September to 1 October with 5 ewes (14.90 LUD over 28 days);
3) Sheep grazed - grazed from 23 April to 15 June with 16 ewes in each plot (92.20 LUD/ha over 54 days), then from 26 July to 1 October grazed as aftermath grazing (i.e. a further 44.02 LUD/ha over 54 days).
Grazing was controlled by electric netting. This was removed on 2 October and each plot was divided in half, one half being fertilised with Nitram (an inorganic fertilizer) at 50 kg/ha using a Vicon PS753H Vari-spreader.
Goose grazing intensity: In the subsequent winter, goose grazing intensity was determined from dropping densities. Five canes were positioned randomly within each plot, and droppings within 1.5 m (area 7.07m²) of a cane were counted and cleared at 4-week intervals (mid-November to mid-March).
Sward height: Sward height was measured five times around each cane using a sward stick, and the avergae calculated. Sward height was measured at the beginning (November 1990) and end (March 1991) of the winter.
In the second year the procedure was repeated, the timing of management was as follows:
Cut - cut for hay 30 June then again in late August;
Cut and aftermath grazed - cut for hay on 26 June then grazed from 30 July to 30 September.
In September the fencing was removed, each plot was divided into three strips (75 x 33 m) and three fertilizer treatments were applied within each. One strip was unfertilized, one was fertilized with Nitram (34.5% nitrogen) at 17.25 kg N/ha, the third with an organic-based fertilizer, Humber 20 (20% nitrogen) at 17.25 kg N/ha.
In November, two 10 cm diameter cores were taken from each plot. Above ground vegetation was clipped and sorted into live and dead material. The number of live tillers in each was counted and the two youngest leaves (young leaves are preferentially grazed by brent geese) used for chemical analysis. In May 1992, sward species composition in each plot was determined. Ten 0.5m² quadrats were randomly placed per plot and the percentage cover of each species estimated.
Grazing intensity: There were no significant differences in grazing intensity of brent geese between treatments in the following comparisons: a) cutting for silage or sheep grazing or cutting and aftermath grazing with sheep; b) grazing with cattle or grazing with sheep; or c) cutting two, three, four or five times.
Sward characteristics: The physical structure and composition of swards resulting from the different management regimes were very similar. The height of all swards in October was <5-6 cm and the biomass of live grass, the live:dead ratio of grass, tiller density and individual tiller weight varied little between regimes. The species composition also varied little between treatments.
Effect of fertilizer: Fertilizer applied at 50 kg N/ha significantly increased the use of the sward by brent geese compared with areas left unfertilized. Application at a lower rate (18 kg N/ha) had no significant effect. There was no difference between the use of areas treated with organic compared with inorganic fertilizer. Protein content of the sward was significantly higher in fertilized compared with unfertilized areas, and in sheep grazed swards compared with swards cut for silage.
Conclusion: In terms of encouraging brent geese onto pasture, of the treatments tested only the application of fertilizer significantly increased grazing intensity by geese.
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