One successful strategy to improve the sustainability of agricultural systems is to promote crop varieties that present high nutrient use efficiency, particularly nitrogen, and are resistant to air pollution. Nitrogen, as a nutrient, is essential to maintain food production but if applied in excess nitrogen losses from agricultural systems occur generating air and water pollution problems. In light of this, one of the biggest challenges of today’s agriculture is to increase nitrogen use efficiency while maintaining yield and quality of crop production . By evaluating genotypic and functional variability of a suit of crop varieties, it is possible to select those varieties that have better coping mechanisms to adapt to low levels of nitrogen. For example, in the case of wheat and other cereals it is possible to select varieties best suited to low levels of fertilization by analyzing the activity of the glutamine synthetase enzyme that play a fundamental role in nitrogen assimilation . The Plant Breeding group (MGP) develops its research line following this approach within the AGRISOST consortium.
The selection of crop varieties with high nitrogen use efficiency also affects crop resistance to air pollution and as a result crop yield and quality. In particular, the availability of nitrogen can counteract the negative effects of air pollution on the production of crops. For example, the Ecotoxicology of Atmospheric Pollution Group (GECA) forming part of the consortium AGRISOST noted that environmental ozone levels may be sufficient to decrease the production of biomass in pastures. Increased nitrogen availability can offset the negative effects of ozone on biomass when concentrations are moderate, but not when ozone concentrations are high. GECA found that ozone limits the fertilizing effect of increased nitrogen input. At present, we have little information about the relationship between levels of fertilization and resistance to air pollution in crops. In AGRISOST, MGP group from the Technical University of Madrid and GECA group from CIEMAT work together to select wheat varieties adapted to low nitrogen and high ozone exposure. By determining the exposure / response function to different ozone levels it is possible to establish when ozone damage occurs in crops and determine whether fertilization can alter this function. Therefore, it is possible to develop Policies to protect crop production from contamination and develop more sustainable agricultural practices.
 Tilman, D., Cassman, K.G., Matson, P.A., Naylor, R., Polasky, S., 2002. Agricultural sustainability and intensive production practices. Nature 418,671–677
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