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RAPID INCORPORATION OF SOLID MANURE AS A BEST
MANAGEMENT PRACTICE?
RE Thorman 1 , J Webb 2 and S Yamulki 3
1
ADAS Boxworth, Battlegate Road, Boxworth, Cambridge, CB3 8NN, UK, E-mail:
rachel.thorman@adas.co.uk; 2 ADAS Wolverhampton, Wergs Road, Wolverhampton,
WV6 8TQ, UK; 3 IGER North Wyke, Okehampton, Devon, EX20 2SB, UK
SUMMARY
After solid manure spreading, rapid incorporation by ploughing has been recognised
as a successful technique to reduce ammonia (NH 3
) emissions. However, the reduced
NH 3
loss conserves nitrogen which may subsequently be emitted from the soil as the
greenhouse gas, nitrous oxide (N 2
O). Emissions of N 2
O were monitored at two UK
sites (central and south west England) after application of cattle manure, pig manure,
layer manure and broiler litter to arable land. At both sites, ploughing reduced NH 3
emissions compared with those from plots where manure remained on the soil surface
(P < 0.001). However, the effect of incorporation on N 2
O loss was inconsistent. In the
warm and wet south west, incorporation had no effect on N 2
O emissions (P > 0.05),
but at the cooler and drier central site, N 2
O losses increased (P < 0.001), suggesting
that rapid incorporation may be considered as a best management practice (BMP)
for both N 2
O and NH 3
abatement only under site-specific conditions.
INTRODUCTION
Around 43 million tonnes of solid manure are handled annually in the UK (Williams et al.,
2000), with 36% of agricultural ammonia (NH 3
) emissions (82 kt N) estimated to arise
from the management of solid manures (Misselbrook et al., 2000). After land spreading,
ammonia emissions of manures represent both a large loss of potential crop available
nitrogen and a considerable environmental risk. Deposition of NH 3
can lead to soil
acidification and nitrogen (N) enrichment of sensitive habitats, consequently the UK
has signed a number of international agreements [UNECE Gothenburg Protocol, EC
Integrated Pollution Prevention and Control (IPPC) Directive, EC National Emission
Ceilings Directive] to reduce NH 3
emissions. After the application of solid manures
to arable land, rapid incorporation has been identified as an effective measure to
abate NH 3
emissions (Webb et al., 2005). However, the reduced NH 3
loss conserves
N increasing the mineral N pool in the soil, which may subsequently be available
for microbial nitrification and denitrification and the production of the greenhouse
gas, nitrous oxide (N 2
O). Nitrous oxide is a potent greenhouse gas with a global
warming potential 310 times that of carbon dioxide (IPCC, 1996). The current UK
emissions inventory (2003) shows that 67% of N 2
O is produced from agriculture with
the majority emitted from agricultural soils (Baggott et al., 2005). As a result of the
Kyoto protocol, the UK has agreed to a legally binding reduction of greenhouse gas
emissions of 12.5% of 1990 levels by the period 2008–12. It is, therefore, important
that measures implemented as a BMP to reduce NH 3
emissions do not result in an
increased loss of N 2
O.
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