Carbon Sequestration and Fertilization Management: Effects of Different Sources on N2O and CO2 Emissions

The potential of different fertilization management to influence soil carbon sequestration and N₂O and CO₂ emissions was studied in a field experiment in the Po river valley (Italy) using a completely randomized design with 3 replications. Fertility treatments included 0 kgN/ha (0N), 130 kg urea-N/ha (TRA), Vicia Villosa as a winter cover-crop (SOV), and compost (COM). Corn for silage was planted on the same day the plots were fertilized and ploughed.

Fluxes of N₂O and CO₂ during the 2007 growing season were monitored two to five times each week following fertilization + tillage and the first irrigation. Three static chambers per plot were used and analyses were conducted using a field photoacoustic multi-gasmonitor. Soil samples (0-7.5 cm depth) were collected the day before and the day after fertilization + tillage and the first irrigation and then weekly to measure mineral nitrogen (NO₃^- + NH₄⁺), potential denitrification, potentially mineralizable nitrogen in anaerobiosis; soil moisture and soil temperature were monitored daily.

N₂O fluxes were more influenced by the tillage + fertilization and less influenced by first irrigation. COM and 0N showed significantly lower N₂O emissions than did SOV and TRA. CO₂ emissions were enhanced by tillage + fertilization and by irrigation. COM and SOV showed higher fluxes of CO₂ even if no significant differences were found on many dates.

Although not statistically significant during the fertilization + tillage, but was during the irrigation period, the mineral nitrogen content was highest in TRA. Potential denitrification was significantly greater in COM, followed by SOV and then by TRA. TRA level was similar to 0N. Potentially mineralizable nitrogen was higher in organic fertilizers (COM, SOV) even if no significant differences were found.

These preliminary results show a great potential of fertilization with compost to reduce GHG emission.