1. Emissions of nitrous oxide and methane after field application of liquid organic fertilizers and biochar.
- Author
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Efosa, Norah, Krause, Hans-Martin, Hüppi, Roman, Krauss, Maike, Vaucher, Nadège, Zourek, Flora, Mayer, Jochen, Six, Johan, and Bünemann, Else K.
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LIQUID fertilizers , *BIOCHAR , *NITROUS oxide , *ORGANIC fertilizers , *GREENHOUSE gases , *FERTILIZER application , *SILAGE , *SOIL amendments - Abstract
The use of anaerobic digestates as fertilizer is proposed as a means to close agricultural nutrient cycles. However, digestates have higher inorganic nitrogen contents than raw manures, which could translate into increased emissions of potent greenhouse gases such as nitrous oxide (N 2 O) and methane (CH 4). To mitigate these emissions, the addition of biochar with high nutrient absorption capacity is suggested. To quantify the effects of anaerobic digestion and biochar amendment on N 2 O and CH 4 emissions, we conducted a study over 33 months with four different crops (silage maize, winter wheat, winter barley, and forage grass). We measured soil parameters such as mineral nitrogen, moisture, and temperature. The N 2 O emissions after application of digestates were generally similar to those observed after cattle slurry or mineral fertilizer application. The highest N 2 O emissions were observed in the first year of the experiment during maize cultivation and were strongly influenced by high soil nitrate concentrations, which were likely linked to enhanced soil organic N mineralization after ley termination. The CH 4 emissions were mostly negative. The addition of biochar to co-digested manure before application at an annual rate of 2 t ha− 1 had no effect on N 2 O emissions but led to short-lived CH 4 peaks from organic fertilizers directly after spreading. We conclude that digestates do not promote larger N 2 O emissions than mineral fertilizers or cattle slurry, and that biochar addition to digestates in small application quantities does not reduce N 2 O emissions but bears the risk of CH 4 release. • N 2 O emissions were strongly affected by crop and position in the rotation. • Highest N 2 O emissions in maize after grass-clover ley. • No consistent effect of mineral vs. liquid organic fertilizers on N 2 O emissions. • Biochar amendment to digested manure did not alter field N 2 O emissions. • Short-lived CH 4 peaks after biochar amendment to digested manure at field application. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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