The effect of chemical and organic N inputs on N2O emission from rain-fed crops in Eastern Mediterranean

Abstract

Nitrogen has a significant contribution to global warming and its reduction in agriculture is expected to reduce N₂O emissions having however adverse effects on the productivity of agricultural ecosystems. Maintaining systems productivity with alternative N sources i.e manure and composts could be a strategy also to mitigate N₂O emissions. In this paper, we present the effect of different N sources (organic and chemical) on field N₂O emissions and how these emissions are associated with soil available N forms (NH₄⁺ and NO₃^-) in three different rain-fed crops namely barley, pea and vetch grown in Cyprus for two growing seasons. The daily emissions ranged from -3.11 to 12.3 g N-N₂O/ha/day, while cumulative emissions ranged from 119 g N-N₂O/ha to 660 g N-N₂O/ha depending on crop and nitrogen source type. The emissions showed a seasonal pattern and WFPS has been identified as a critical soil parameter controlling daily N₂O emissions. The daily N₂O fluxes in the current study derives mainly from nitrification irrespectively crop type or nitrogen source type. Specific emission factors for each crop cultivated under different N source type were calculated and ranged from 0.03% ± 0.02-0.34% ± 0.09. The application of manure and chemical fertilizers cause similar intensity of N₂O emissions while compost exhibited the lower emission factors. These findings suggest that composts could be integrated in a nutrient management strategy of rain-fed crops with less N₂O emissions. The high background emissions found suggest also that other factors than external inputs are associated with N₂O emissions and further studies including the response of microbial community structure and their contribution and association with N₂O emissions.

Keywords: Climate change; Emission factors; N(2)O; Nutrient management.