Nitrous oxide, methane and ammonia emissions following slurry spreading on grassland
Rodhe, L.P.ll, M.Y.mulki, S.
Soil use and management 22(3): 229-237
ISSN/ISBN: 0266-0032 DOI: 10.1111/j.1475-2743.2006.00043.x
In Sweden, 90% of ammonia (NH subscript 3(B) emissions to the atmosphere originate from agriculture, predominantly from animal manure handling. It is well known that incorporation of manure into soil can reduce NH subscript 3(B emissions after spreading. However, there is a risk of increased nitrous oxide (N subscript 2(BO) and methane (CH subscript 4(B) emissions caused by bacterial activity and limited oxygen availability under these conditions. A full-scale injector was developed and evaluated in a field experiment on grassland. Cattle slurry was either injected in closed slots 5 cm below ground or band spread on the soil surface above the crop canopy at a rate of 25 t ha superscript -1(B. In a control treatment, no slurry was applied. During a 5-day period after application, NH subscript 3(B emissions were measured using an equilibrium concentration method. Gas samples for estimating CH subscript 4(B and N subscript 2(BO emissions were also collected during 7 weeks following slurry application. Injection in closed slots resulted in no detectable NH subscript 3(B emissions. After band spreading, however, NH subscript 3(B emissions corresponded to nearly 40% of the total ammoniacal nitrogen in the applied slurry. The injection of slurry gave rise to a broad peak of N subscript 2(BO emissions during the first 3 weeks after application. In total, for the measuring period, N subscript 2(BO emissions corresponded to 0.75 kg N ha superscript -1(B. Band spreading resulted in only a very small N subscript 2(BO release of about 0.2 kg N ha superscript -1(B during the same period. Except for the first sampling occasion, the soil was predominantly a sink for CH subscript 4(B in all the treatments. The use of the injector without slurry application reduced grass yield during unfavourable growing conditions. In conclusion, shallow injection in closed slots seems to be a promising technique to reduce negative environmental impacts from NH subscript 3(B emissions with a limited release of N subscript 2(BO and CH subscript 4(B.