Does the use of digestate to replace mineral fertilizers have less emissions of N_2O and NH_3?

摘要

Digestate is considered a sustainable opportunity to reduce environmental impact from fertilization, due to high content of nitrogen easily available for plants and for the low impact of its production. We tested liquid fraction of digestate from anaerobic digestion of pig slurries and urea, to assess the emissions of nitrous oxide and ammonia from soil on silage maize (Zea mays L.). Nitrogen rate was the same for both treatments (150kg/ha) spread replacing common methods. Emissions measurements wereperformed immediately after fertilization using a static chamber method with a portable gas analyser. Measurements were performed daily during the first week, and twice per week until no emissions from the soil were observed. Cumulative nitrogen emissions show that digestate can be an efficient method to reduce nitrogen losses (2.87 kg N/ha/25 days and 3.76 kg N/ha/25 days for digestate and urea respectively). However, the two fertilizers emitted different kind of gases: compared to urea, digestate emitted the 23% of nitrous oxide more, on the other hand urea emitted 66% of ammonia more than digestate. Crop yield obtained under the two fertilization methods did not significantly differ in terms of dry matter (DM) (13.631 DM/ha and 13.241 DM/ha for digestate and urea, respectively) (significance factor a > 0.5).