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Nitrous oxide (N 2 O) emissions have been increasing as a result of intensive nitrogen (N) fertilisation. Soil nitrification and denitrification are the main sources of N 2 O, and the use of ammonium-based fertilisers combined with nitrification inhibitors (NIs) could be useful in mitigating N 2 O emissions from agricultural systems. In this work we looked at the N 2 O mitigation capacity of two dimethylpyrazol-based NIs, 3,4-dimethylpyrazole phosphate (DMPP) and 2-(N-3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA), on soil nitrifying and denitrifying microbial populations under two contrasting soil water contents (40% and 80% soil water filled pore space; WFPS). Our results show that DMPP and DMPSA are equally efficient at reducing N 2 O emissions under 40% WFPS conditions by inhibiting bacterial ammonia oxidation. In contrast, at 80% WFPS DMPSA was less efficient than DMPP at reducing N 2 O emissions. Interestingly, at 80% WFPS, where lowered oxygen availability limits nitrification, both DMPP and DMPSA not only inhibited nitrification but also stimulated N 2 O reduction to molecular nitrogen (N 2 ) via nitrous oxide reductase activity (Nos activity). Therefore, in this work we observed that DMP-based NIs stimulated the reduction of N 2 O to N 2 by nitrous oxide reductase during the denitrification process.

A method based in two-dimensional protein gel electrophoresis has been developed in order to improve the analysis of genetic relationships among populations of Globodera. It has been used to estimate genetic divergence among nine Globodera pallida nematode populations. Sixty-one anonymous polypeptide spots were resolved using silver-stained high-resolution 2D gels and they were quantified in each population to establish genetic variation among G. pallida populations. The results of this analysis were compared with those obtained after a study of allelic frequency variation, which was carried out using seven previously described loci. Genetic distances among populations were calculated by means of both studies, the quantitative analysis and the allelic frequency variation, and phylogenetic trees were constructed for each type of analysis. A correlation analysis between the two distance matrices was carried out and a bootstrap analysis was performed to determine the strength of the clusters obtained with each method. The results obtained support the idea that quantitative protein analysis can be successfully applied to phylogenetic analysis of G. pallida populations.