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ECONOMIC IMPLICATIONS OF MINIMISING DIFFUSE
NITROGEN POLLUTION FROM LIVESTOCK MANURES
BJ Chambers 1 , JR Williams 2 , E Sagoo 2 , KA Smith 3 and DR Chadwick 4
1
ADAS Gleadthorpe, Meden Vale, Mansfield, Notts., NG20 9PF, UK, E-mail: brian.
chambers@adas.co.uk; 2 ADAS Boxworth, Battlegate Road, Boxworth, Cambridge,
CB3 8NN, UK; 3 ADAS Wolverhampton, Wergs Road, Woodthorne, Wolverhampton
WV6 8TQ, UK; 4 IGER North Wyke, Okehampton, Devon, EX20 2SB, UK
SUMMARY
The economic implications of additional financial investment in extra slurry storage
capacity and improved manure spreading equipment to reduce diffuse nitrogen
pollution from livestock manure management was assessed for six ‘model’ livestock
(two pig, three cattle and one broiler) farms. On the pig and dairy farms, the investment
in additional slurry storage required to avoid the need to apply slurry in the autumn
was between £3,500 and £5,880/year (amortised over 20 years), compared with an
increased fertiliser N replacement value of the slurry (as a result of reduced leaching
losses) of between £180 and £760/year. The cost of the bandspreading equipment
was c. £3,250/year (amortised over 10 years) compared with the increased fertiliser
N replacement of the slurry N (as a result of reduced ammonia losses) of between
£230 and £330/year on the pig and dairy farms. On the broiler farm, reducing N
leaching losses by changing the application timing from autumn to spring increased
the fertiliser N replacement value of the broiler litter by £3,860/year, compared
with the cost of the improved spreading equipment at £2,860/year (amortised over
10 years). Studies quantifying both nitrate leaching and ammonia volatilisation losses
have clearly shown that an integrated approach to slurry N management is needed,
so that management policies that aim to reduce nitrate leaching do not exacerbate
other N loss pathways (so called ‘pollution swapping’).
INTRODUCTION
In the UK each year, approximately 90 million tonnes of livestock manures (47 million
tonnes of slurry and 43 million tonnes of solid manure) supplying 450,000 tonnes of
nitrogen (N) are applied to agricultural land (Williams et al., 2000). Efficient utilisation
of manure nitrogen is essential to reduce diffuse air (e.g. ammonia) and water (e.g.
nitrate) pollution, and to maximise crop N utilisation. The UK is committed to reducing
ammonia emissions and nitrate leaching losses to comply with EU Directives. The
current Nitrate Vulnerable Zone Action Programme (which covers 55%, 14% and
3% of agricultural land in England, Scotland and Wales, respectively) restricts the
application of high available N manures (i.e. pig/cattle slurries and poultry manures)
on sandy and shallow soils in the autumn/early winter period.
On many farms, changing manure application practices to reduce nitrate leaching
losses will require significant financial investment in extra slurry storage capacity
to avoid the need to apply slurry in the autumn. In addition, investment in slurry
bandspreading equipment (e.g. trailing hose and trailing shoe machines; Plate 1) is
likely to be required to apply slurry evenly to growing arable and grassland crops in
spring/summer, without causing damage to soils and reducing crop quality. However,
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