Effects of varying rates of autumn fertilizer applications to pastures in eastern England on feeding sites selection by brent geese Branta b. bernicla

Mark Hassall, Simon J. Lane

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Strategies are needed to reduce damage by wildfowl to agricultural crops. To determine the shape of response curves relating feeding intensity to fertilizer application levels, rates at which nitrogen-based fertilizers were applied to pastures in autumn were varied in randomized block experiments in fields on the north Norfolk coast, eastern England. Site selection by wintering brent geese was monitored by comparing rates at which droppings were deposited on each treatment. In the first experiment, with ammonium nitrate applied on 20 October, at rates below the recommended level of 50 kg N ha-1, a linear increase in grazing intensity in response to fertilizer application rate was observed with 22% more droppings deposited at 36 kg N ha-1 than on control plots. At these application rates the slope of the response curve for ammonium nitrate peaked in November then decreased and was no longer significant from the end of December until March. In the second experiment, with the slow release fertilizer of ammonium sulphate in lignite applied on 29th October over a range of rates three times greater than the recommended rate, a linear response to rates of fertilizer application was again observed but with a significantly lower slope, so that only 9% more droppings were deposited at 36 kg N ha-1 than on the unfertilized controls. Over this wider range of application rates the slope of the response curves remained relatively constant and highly significant until the end of the season in mid-March. The results are discussed in relation to their implications for the cost-effectiveness of managing alternative feeding areas in order to reduce damage by wildfowl to agricultural crops. It is concluded that to increase the attractiveness of alternative feeding areas for brent geese, fertilizers should be applied about 2 weeks before the birds are expected to start using the site, and there should be flexibility in application rates and type of fertilizer used according to the value of the crop and its window of vulnerability to damage by geese.
Original languageEnglish
Pages (from-to)203-209
Number of pages7
JournalAgriculture, Ecosystems & Environment
Issue number2
Publication statusPublished - 2001

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