Effect of fertilising with pig slurry and chicken manure on GHG emissions from Mediterranean paddies

Soil fertilisation affects greenhouse gas emissions. The objective of this study was to compare the effect of different fertilisation strategies on N2O, CH4 emissions and on ecosystem respiration (CO2 emissions), during different periods of rice cultivation (rice crop, postharvest period, and seedling) under Mediterranean climate. Emissions were quantified weekly by the photoacoustic technique at two sites. At Site 1 (2011 and 2012), background treatments were 2 doses of chicken manure (CM): 90 and 170 kg NH4+-N ha− 1 (CM-90, CM-170), urea (U, 150 kg N ha− 1) and no-N (control). Fifty kilogram N ha− 1 ammonium sulphate (AS) were topdress applied to all of them. At Site 2 (2012), background treatments were 2 doses of pig slurry (PS): 91 and 152 kg NH4+-N ha− 1 (PS-91, PS-152) and ammonium sulphate (AS) at 120 kg NH4+-N ha− 1 and no-N (control). Sixty kilogram NH4+-N ha− 1 as AS were topdress applied to AS and PS-91. During seedling, global warming potential (GWP) was ~ 3.5–17% of that of the whole rice crop for the CM treatments. The postharvest period was a net sink for CH4, and CO2 emissions only increased for the CM-170 treatment (up to 2 Mg CO2 ha− 1). The GWP of the entire rice crop reached 17 Mg CO2-eq ha− 1 for U, and was 14 for CM-170, and 37 for CM-90. The application of PS at agronomic doses (~ 170 kg N ha− 1) allowed high yields (~ 7.4 Mg ha− 1), the control of GWP (~ 6.5 Mg CO2-eq ha− 1), and a 13% reduction in greenhouse gas intensity (GHGI) to 0.89 kg CO2-eq kg− 1 when compared to AS (1.02 kg CO2-eq kg− 1).