Use of a novel nitrification inhibitor to reduce nitrous oxide emission from N-15-labelled dairy slurry injected into soil

Recent recommendations for environmentally sound use of liquid animal manur e often include injection of slurry into soil. Two of the most important un desired side effects, ammonia (NH3) volatilisation and odour emissions, are usually significantly reduced by slurry injection. On the other hand, beca use of the higher amount of nitrogen (N) remaining in soil, the risk of nit rate (NO3-) leaching and nitrous oxide (N2O) emissions is increased. Thus, the reduction of local effects caused by NH3 deposition, e.g. N enrichment and soil acidification, may be at the cost of large-scale effects such as o zone depletion and global warming as a result of emitted N2O. In this conte xt, nitrification inhibitors can contribute significantly to a reduction in NO3- leaching and N2O production. A field experiment was carried out at IGER, North Wyke, which aimed to eval uate the effect of the new nitrification inhibitor 3,4-dimethylpyrazole pho sphate (DMPP/ENTEC (TM)). For this experiment, N-15 enriched dairy slurry w as used and the isotopic label in soil N as well as in N2O were studied. Af ter slurry injection into the grassland soil in August 2000, the major emis sions of N2O occurred during the first ten days. As expected, high N2O emis sion rates and N-15 content of the emissions were concentrated on the slurr y injection slots, showing a steep decrease towards the untreated centre-po int between slurry injection slots. The nitrification inhibitor DMPP proved to be very efficient in reducing N2O emissions. At a rate of 2 kg DMPP ha( -1), the total amount of N2O emitted was reduced by 32%, when compared with slurry injection without DMPP. The isotopic label of the emitted N2O showe d that during the 22-day experimental period, emissions from the slurry N p ool were strongly reduced by DMPP from 0.93 kg N2O-N ha(-1) (-DMPP) to 0.50 kg N2O-N ha(-1) (+DMPP), while only a minor effect on emissions from the s oil N pool was observed (0.69 to 0.60 kg N2O-N ha(-1); -DMPP, +DMPP, respec tively). Copyright (C) 2001 John Wiley & Sons, Ltd.