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

Recent recommendations for environmentally sound use of liquid animal manure often include injection of slurry into soil. Two of the most important undesired side effects, ammonia (NH3) volatilisation and odour emissions, are usually significantly reduced by slurry injection. On the other hand, because of the higher amount of nitrogen (N) remaining in soil, the risk of nitrate (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 ozone depletion and global warming as a result of emitted N2O. In this context, 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 evaluate the effect of the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP/ENTEC (TM)). For this experiment, N-15 enriched dairy slurry was used and the isotopic label in soil N as well as in N2O were studied. After slurry injection into the grassland soil in August 2000, the major emissions of N2O occurred during the first ten days. As expected, high N2O emission rates and N-15 content of the emissions were concentrated on the slurry injection slots, showing a steep decrease towards the untreated centre-point 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 showed that during the 22-day experimental period, emissions from the slurry N pool 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 soil N pool was observed (0.69 to 0.60 kg N2O-N ha(-1); -DMPP, +DMPP, respectively). Copyright (C) 2001 John Wiley & Sons, Ltd.