Original in spanish: http://www.madrimasd.org/informacionidi/noticias/noticia.asp?id=30556&tipo=g
Soils are important emitters of greenhouse gases (N2O, CH4 and CO2) and of reactive nitrogen gases (NO, NO2, NH3). It is estimated that 65% of the N2O emitted to the atmosphere come from agricultural and forest soils and, as it is known, a single molecule of this gas has 296 times the effect on climate change than a CO2 molecule. Other compounds emitted such as nitrogen oxides (NOx), a precursor of tropospheric ozone, and ammonia (NH3), that contributes to the degradation of the ecosystems through acid rain, are emitted in an important percentage by agricultural soils.
Against this background, investigators of the E.T.S.I. Agronomists and the E.U.I.T. Agriculturist of Madrid, members of the investigation group "Contamination of Agroecosistemas by Agricultural Practices" of the Polytechnical University of Madrid, participate in investigation projects (national and European) in which they intend to study the mechanisms responsible for these emissions and to establish proposals of agricultural practices that take to the mitigation of the emissions of these gases from agricultural soils.
The studies initiated already several years ago have been giving conclusive results. It has been possible to demonstrate that acting on the nitrogen fertilization it is possible to reduce in a remarkable way the nitrogen gas discharges. In particular, the use of organic fertilizer, like manure or crop residue, can constitute an effective strategy to reduce the oxide emissions of N in comparison to mineral fertilizers. This takes place as a result of which the soluble C, incorporated with organic fertilizers, has a beneficial effect in the transformation of N2O to N2 through one of the main processes responsible for the emissions: the biological denitrification. It has been possible to demonstrate that this effect is more intense in soils with little organic matter, as it corresponds to those of barren and semi-arid zones, than in grounds with an elevated content more in organic matter. In this same line, and collaboration with British investigators, this group has concluded that acting on the diet of the cattle it is possible to reduce future nitrogen oxide emissions, which affects the fractions of hydrocarbon and nitrogen gases of animal manure.
Another front of performance that has given positive results has been the use of inhibiting substances nitrification processes and urea on the soils that can reduce oxide emissions of nitrogen and ammonia, respectively, in the first weeks after the urea fertilizer contribution. Next to the results of these studies, a finding that can have importance for agricultural emissions, and in particular for the future of the agriculture of our country, is the handling of the irrigation combined with nitrogen fertilization. These investigators have been able to demonstrate that irrigation by dripping, effective for the reduction of the water consumption, also mitigates nitrogen oxide emissions as opposed to other systems of irrigation. The study is highly novel, since it is not known if similar studies in other countries have been carried out.
Finally, it has been stated by this group that agricultural soils act as a sink for CH4 coming from activities of human origin. This takes place through its oxidation by present methanotrophic micro-organisms in all soils. At the present time, these Madrilenian investigators maintain experiments to quantify the most favourable magnitude of this effect and conditions so that this takes place. Also, experiments on field in which they are moderated in a systematic way are carried out and frequently, manifold parameters related to the soil emissions of the Community of Madrid are measured. The results are transferred to a data base managed by the European project Nitroeurope IP, which will allow to validate predictive mathematical models of the emissions in different agricultural systems for the decision making from a scale of European agrarian policy.