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Table 1: Broadcast and trailing shoe slurry application details (March 2004)
Application
rate (m3/ha)
N applied
(kg/ha)
Surface area occupied
by band spread slurry
(%)
Hydraulic loading rate (mm)
Broadcast Trailing shoe
20 91 18 2.0 11
35 159 22 3.5 16
50 227 26 5.0 19
65 295 30 6.5 22
80 363 27 8.0 30
CONCLUSIONS
Shallow injection of slurry into the clay loam grassland soil (at application rates
between 20 and 80 m 3 /ha) reduced NH 3
emissions by c. 60% compared with
surface broadcast application, largely as a result of the smaller emitting surface area.
Although there was some ‘overspill’ from the injection slots at the higher application
rates, the majority of the slurry remained within the slot and this did not affect NH3
emissions as a % of the total N applied.
Slurry application using a trailing shoe did not reduce NH 3
emissions compared with
surface broadcast application. Although the slurry remained within a band (surface
area occupied 18–30%), the combination of a high hydraulic loading rate (11–30 mm)
and wet soil conditions restricted the rate of slurry infiltration into the soil, which
resulted in similar NH 3
losses to the broadcast application.
These data indicate that for slurry shallow injection and bandspreading techniques to
successfully reduce NH 3
emissions, slurry needs to be retained in a band/slot (to give
a smaller emitting surface area) and to rapidly infiltrate into the soil. If both conditions
are not satisfied, the NH 3
reduction benefit of bandspread/shallow injection spreading
techniques will not be realised.
ACKNOWLEDGEMENTS
Funding of this work by Defra is gratefully acknowledged.
REFERENCES
Basford WD, Briggs W, Jackson DR and Smith KA (1996). Equipment for the improved
precision application of animal waste slurries and liquid effluents to field plots. In:
Proceedings of the International Conference on Mechanisation of Field Experiments
(IAMFE ‘96), IAMFE, Paris/Versailles, France, pp. 161-166.
Defra (2002). Ammonia in the UK. Defra Publications, London.
Lockyer DR (1984) A system for the measurement in the field of losses of ammonia
through volatilisation. Journal of the Science of Food and Agriculture 35, 837–848.
Smith KA, Jackson DR, Misselbrook TH, Pain BF and Johnson RA (2000). Reduction
of ammonia emissions by slurry application techniques. Journal of Agricultural
Engineering Research 77, 277–287.
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