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Abstract: A series of environmental policies have been implemented in the European Union (EU) to decrease nitrogen (N) emissions from agriculture. The Nitrates Directive (ND) is one of the main policies; it aims to reduce nitrate leaching from agriculture through a number of measures. A study was carried out to quantify the effects of the ND in the EU-27 on the leaching and runoff of nitrate (NO3 −) to groundwater and surface waters, and on the emissions of ammonia (NH3), nitrous oxide (N2O), nitrogen oxides (NOx) and dinitrogen (N2) to the atmosphere. We formulated a scenario with and a scenario without implementation of the ND. The model MITERRA-Europe was used to calculate N emissions on a regional level in the EU-27 for the period 2000–2008. The calculated total N loss from agriculture in the EU-27 was 13Mton N in 2008, with 53% as N2, 22% as NO3, 21% as NH3, 3% as N2O, and 1% as NOx. The N emissions and leaching in the EU-27 slightly decreased in the period 2000–2008. Total emissions in the EU in 2008 were smaller with implementation of the ND than without the ND, by 3% for NH3, 6% for N2O, 9% for NOx, and 16% for N leaching and runoff in 2008. However, regional differences were large. The lower emissions with ND were mainly due to the lower N inputs by fertilizers and manures. In conclusion, implementation of the ND decreased both N leaching losses to ground and surface waters, and gaseous emissions to the atmosphere. It is expected that the ND will result in a further decrease in N emissions in EU-27 in the near future, because the implementation of the measures for the ND is expected to become more strict. [Copyright &y& Elsevier]

Abstract: Ammonia oxidizers, including ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) are important drivers of a key step of the nitrogen cycle — nitrification, which affects the production of the potent greenhouse gas, nitrous oxide (N2O). A field experiment was conducted to determine the effect of nitrogen application rates and the nitrification inhibitor dicyandiamide (DCD) on the abundance of AOB and AOA and on N2O emissions in a grazed pasture soil. Nitrogen (N) was applied at four different rates, with urea applied at 50 and 100kgNha−1 and animal urine at 300 and 600kgNha−1. DCD was applied to some of the N treatments at 10kgha−1. The results showed that the AOB amoA gene copy numbers were greater than those of AOA. The highest ratio of the AOB to AOA amoA gene copy numbers was 106.6 which occurred in the urine-N 600 treatment. The AOB amoA gene copy numbers increased with increasing nitrogen application rates. DCD had a significant impact in reducing the AOB amoA gene copy numbers especially in the high nitrogen application rates. N2O emissions increased with the N application rates. DCD had the most significant effect in reducing the daily and total N2O emissions in the highest nitrogen application rate. The greatest reduction of total N2O emissions by DCD was 69% in the urine-N 600 treatment. The reduction in the N2O emission factor by DCD ranged from 58% to 83%. The N2O flux and NO3 −-N concentrations were significantly correlated to the growth of AOB, rather than AOA. This study confirms the importance of AOB in nitrification and the effect of DCD in inhibiting AOB growth and in decreasing N2O emissions in grazed pasture soils under field conditions. [Copyright &y& Elsevier]