Soil carbon emissions from maize under different fertilization methods in an extremely dry summer in Italy

During the last decades, climate change and variability are increasingly and negatively affecting agriculture. To ensure satisfactory and stable food production, agriculture is intensifying the adoption of external input with environmental consequences such as the emission of greenhouse gases. In this experiment, we monitored CO2 and CH4 emission dynamics from cultivation of maize for silage grown under different fertilization treatments: (i) liquid fraction of digestate from pig slurries, (ii) urea, and (iii) no fertilization (control), in an extremely dry summer in Central Italy. Results show that the use of the liquid-organic fertilizer (digestate) significantly increased CO2 emissions from soil (685.29 kg-C ha-1) compared to the conventional fertilizer (urea) (391.60 kg-C ha-1). However, CH4 emissions were comparable between the two fertilizers and almost negligible compared to those of CO2. In both treatments CH4 emissions were enhanced by the only precipitation event, coupled with an increase of air temperature. Effectiveness of tested fertilizers was assessed through a yield analysis, and proved that digestate may represent a viable alternative to urea (6.97 and 6.48 t ha-1). Nevertheless, considering CO2 emissions from digestate and the numerous passes in field needed for its spreading, the use of this fertilizer in extreme dry conditions requires specific considerations.