Ammonia emissions from different fertilizing strategies in Mediterranean rainfed winter cereals

- Dry matter of slurry (PS) and soil water content control NH3 losses in dryland systems.
- PS dry matter (DM) around 4% is associated to the highest percentage of TAN losses.
- Low slurry DM (0.8%) accounts for similar NH3 losses and yields than NH4NO3 fertilizer.
- NH3 losses from well managed PS (the highest yields) can be in between 8 and 20 kg N ha−1.
- PS applied only at tillering achieved maximum yields in dryland systems.

Anthropogenic ammonia (NH3) emissions mainly result from agricultural activities where manure spreading plays a significant role. For a Mediterranean rainfed winter cereal system there is a lack of data regarding NH3 emissions. The aim of this work is to provide field data on N losses due to NH3 volatilization as a consequence of the introduction of slurries in fertilization strategies and also, to assess the influence of environmental conditions and slurry characteristics on emissions. The fertilizing strategies include the use of slurry from fattening pigs (PS), sows (PSS) and/or mineral fertilizer (M) as ammonium nitrate. Fertilizers were spread over the calcareous soil at sowing and/or at tillering at rates from 15 to 45 kg NH4+-N ha−1 for M and from 48.8 to 250.3 kg NH4+-N ha−1 for slurries. The NH3 emissions were quantified during three cropping seasons. Average losses from the total ammonium nitrogen applied ranged from 7 to 78% for M and from 6 to 64% for slurries and they were not directly proportional to the amounts of applied ammonium. The best results on NH3 volatilization reduction were registered when soil water content (SWC, 0-30 cm) was below 56% of its field capacity and also, when slurry dry matter (DM) was in the interval of 6.1-9.3% for PS or much lower (0.8%) for PSS. High slurry DM favoured crust formation and the lower rates promoted infiltration, both of which reduced NH3 emissions. Nevertheless, at tillering, the lower DM content was the most effective in controlling emissions (<9 kg NH3-N ha−1) and equalled M fertilizer in cumulative NH3 loss (p > 0.05). A single slurry application at tillering did not negatively affect yield biomass. The combining of recommended timing of applications with slurry DM content and SWC should allow producers to minimize volatilization while maintaining financial benefits.