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 170kgNH4(+)-Nha(-1) (CM-90, CM-170), urea (U, 150kgNha(-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 152kgNH4(+)-Nha(-1) (PS-91, PS-152) and ammonium sulphate (AS) at 120kgNH4(+)-Nha(-1) and no-N (control). Sixty kilogram NH4(+)-Nha(-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 2MgCO2ha(-1)). The GWP of the entire rice crop reached 17Mg CO2-eqha(-1) for U, and was 14 for CM-170, and 37 for CM-90. The application of PS at agronomic doses (~170kgNha(-1)) allowed high yields (~7.4Mgha(-1)), the control of GWP (~6.5MgCO2-eqha(-1)), and a 13% reduction in greenhouse gas intensity (GHGI) to 0.89kgCO2-eqkg(-1) when compared to AS (1.02kgCO2-eqkg(-1)).
Nitrous oxide (N2O) is a gas of environmental concern that can be emitted during nitrification and denitrification. Molecular nitrogen (N2) is the ultimate product of denitrification. The emission of both gases represents an economic loss. This study quantified daily and seasonal N2O and N2 emissions from three benchmark arable soils sown with maize (Zea mays L.) in Catalonia (northeast Spain) during the irrigation season, and identified the major factors and processes determining these emissions. The N2O was sampled using the closed chamber method, and N2 from N2O that accumulated with the acetylene inhibition method, simultaneously in the field. At water‐filled pore space (WFPS) >70%, losses amounted to 389 g of N2O‐N ha−1 d−1 from the El Pinell site, 144 g of N2O‐N ha−1 d−1 from the Barbens site, and 125 g of N2O‐N ha−1 d−1 from the Bellpuig site. Most of the N was lost through complete denitrification. Up to 640 g of N2‐N ha−1 d−1 were lost from the El Pinell site, 1438 g of N2‐N ha−1 d−1 from the Barbens site, and 233 g of N2‐N ha−1 d−1 from the Bellpuig site. Negative N2O and N2 fluxes were found. Total (N2O + N2)‐N losses represent 13.6% of the N applied at the El Pinell site, 8.6% at the Barbens site, and 1.7% at the Bellpuig site. Denitrification was the main source of emission. Significant N2O‐N losses due to nitrification were also measured. The potential for gaseous N losses from these soils at <40% WFPS is low (it averaged 0.01 g of N ha−1 d−1 from the three sites).
The intensive breeding of beef cattle in Juncosa de les Garrigues (Catalonia, Spain) leads to the production of a large volume of manure that needs appropriate management. Land application in the area at agronomic rates is not enough to ensure good management practices, making necessary extended on-farm storage and the export of part of the production to long distances. In this context, the implementation of a collective treatment based on composting could help in enhancing the handling of manure. We assessed a full-scale composting process based on turned windrows (W), and involving treatment of beef cattle manure (CM) alone (two typologies were considered according to carbon-to-nitrogen ratios of ~25 (CM1, W1) and ~14 (CM2, W2)), or mixed with bulking agent (CM2/BA, W3) and dewatered digested sewage sludge (CM2/BA/DDSS, W4). Composting significantly improved the transportability of nutrients (final volumes were 40-54% of the initial volume). Temperature >55°C was reached in all the treatments but following different time patterns. Under the applied conditions of turning and rewetting, 14 weeks of processing did not ensure the production of stable, and mature, compost. Thus, only compost from W1 attained the maximum degree of stability as well as concentration of ammonium-N < 0.01% (with ammonium-N/nitrate-N ratio of 0.2) and low phytotoxicity. However, high pH, salinity, and heavy metal contents (Cu and Zn) may limit its final use. Addition of BA was advised to be kept to minimum, whereas use of DDSS as a co-substrate was not recommended in agreement to the higher loss of N and levels of heavy metals in the final compost.
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