Fertilize artificial grasslands

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 4
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How is the evidence assessed?

Effectiveness

60%
Certainty

35%
Harms

7%

Calculating overall effectiveness category

Background information and definitions

Fertilised grasslands are likely to have higher productivity and therefore support larger numbers of birds, particularly grazing species, such as geese. This intervention is commonly used to attract geese to specific areas to reduce conflict with farmers, when geese graze their crops. See ‘Provide sacrificial grasslands to reduce the impact of wild geese on crops’.

Study locations

Key messages

We captured four studies examining the impacts of fertilizing grasslands, all from the UK and investigating grazing by geese Anser and Branta spp. Two studies found that more geese grazed on areas that were fertilised compared with control areas. Two studies found that cut and fertilised areas were used more than control areas. One study found that fertilised areas were used less than re-seeded grasslands.
One study found that fertilisation affected grazing at applications of 50 kg N/ha, but not 18 kg N/ha. One study found that grazing rates only increased with applications of up to 80 kg.N/ha.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, controlled trial in the winter of 1972-1973 at a 6 ha pasture (periodically flooded by saltwater) in Gloucestershire, UK (Owen 1975), found that significantly more greater white-fronted geese Anser albifrons fed on fertilised and cut areas, compared to control areas (overall average of 30-35% of geese on cut, fertilised areas vs. 17-20% on control areas; maximum of 65% use of cut, fertilised areas vs. 20% for controls). Preferences decreased over time as preferred areas lost vegetation and became more crowded. Vegetation from experimental areas had a higher nitrogen content than that from control areas. Fertilisation consisted of 125 kg/ha of ‘nitro-chalk’ – 25% nitrogen – applied in mid October. In mid-October, the grass was also cut to approximately 8 cm.
Study and other actions tested
Referenced paper
Owen M. (1975) Cutting and Fertilizing Grassland for Winter Goose Management. Journal of Wildlife Management, 39, 163-167.
A replicated, controlled study in 1984-1987 on a reserve on the island of Islay, west Scotland (Percival 1993), found that more barnacle geese Branta leucopsis used wet pasture fields if they were fertilised, compared to control fields (17-42% higher dropping densities in fertilised fields, but not in all fields or years). However, fewer geese used fertilised fields than re-seeded ones. Fertilisers were either 34.5% nitrogen in pellet form (at 125 kg/ha), or ‘Nitrochalk’ – 25% nitrogen in granular form – (at 175 kg/ha) and spread in October (wet and dry fields) and March (dry fields only).
Study and other actions tested
Referenced paper
Percival S.M. (1993) The effects of reseeding, fertilizer application and disturbance on the use of grasslands by barnacle geese, and the implications for refuge management. Journal of Applied Ecology, 30, 437-443.
A series of replicated controlled trials on grassland sites at two reserves in Essex, England, between 1990 and 1992 (Vickery et al. 1994) found that brent geese Branta bernicla grazed at significantly higher densities on fertilised and cut areas, compared to unfertilised areas, but only at high levels of fertiliser application (50 kg N/ha used: 28-30 droppings/m² for fertilised areas vs. 23-28 droppings/m² for controls; 18 kg N/ha used: 30-35 droppings/m² for fertilised areas vs. 25-35 droppings/m²for control areas). There were no differences between trials using organic and inorganic fertiliser.
Study and other actions tested
Referenced paper
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.
A replicated, controlled study in 1990-1993 at a reserve in Aberdeenshire, Scotland (Patterson & Fuchs 2001), found that spring fertiliser application in 1990-1 significantly increased the use of grassland fields by pink-footed geese Anser brachyrynchus, until applications of approximately 80 kg N/ha (1990: average of 13-14 goose droppings/m² with no application vs. 18-22 droppings/m² with 40 kg N/ha, 28 droppings/m² with 80 kg/m² and 27-31 droppings/m² with 120-160 kg N/ha; patterns in 1991 were similar but with fewer droppings). However, two slow-release fertilisers did not affect foraging densities in winter 1990-1992 (average of 24.5-26.7 droppings/m² for fertilised vs. 24 droppings/m² for control grasslands). Split fertiliser application did not increase field use, compared to a single application (average of 11 droppings/m² for fields with split applications vs. 10 droppings/m² for single applications), although the authors note it may reduce nitrogen leeching.
Study and other actions tested
Referenced paper
Patterson I.J. & Fuchs R.M.E. (2001) The use of nitrogen fertilizer on alternative grassland feeding refuges for pink-footed geese in spring. Journal of Applied Ecology, 38, 637-646.

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2020) Bird Conservation. Pages 137-281 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Bird Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Employ grazing in non-grassland habitats Action Link	Trade-off between benefit and harms	8	Synopsis Link
Re-seed grasslands Action Link	Unknown effectiveness (limited evidence)	2	Synopsis Link
Apply herbicide to mid- and understorey vegetation Action Link	Likely to be ineffective or harmful	7	Synopsis Link