Mitigation of carbon dioxide and nitrous oxide emissions from soil : Elucidating the impacts of nitrification inhibitors, environmental factors, soil characteristics and biogas residues acidification

The mineral N fertilizer (NH4+) and the organic N fertilizer (biogas residues) applied to fertilize soils may lead to higher CO2 and N2O emissions. Nitrification inhibitors (NIs) and chloride are used to curb this effect. However, their effectiveness is strongly influenced by environmental factors, soil and fertilizer properties. This study investigated how different NIs and chlorides behave under different environmental factors, soil and fertilizer properties. In an incubation experiment the efficacies of four NIs (DCD, DMPP, ENTEC and PIADIN) and two chlorides (KCl and MgCl2) under different environmental factors (two soil temperatures (15 and 25 °C), two moisture levels (60% and 80% water holding capacity)), three types of soils (clay, loam and sand) and two types of fertilizer (biogas residues and acidified biogas residues) were tested for 8 weeks. The soil received 0.5 g NH4+-N kg-1 soil and the inhibitors were applied at 5% of the applied N. KCl and MgCl2 were applied at 0.5 and 1.0 g kg-1, respectively. The results of this study show that DMPP and PIADIN were more effective than DCD and ENTEC in inhibiting nitrification in sandy soils at 15 and 25 °C and at 60% and 80% water holding capacity. The efficacy of all nitrification inhibitors improved with increasing soil moisture, while increasing temperatures had various negative effects on the sandy soil used. 1.0 g kg-1 MgCl2 reduced both CO2 and N2O emissions. The acidified biogas residues had less influence on the increased CO2 and N2O emissions compared to the unacidified biogas residues. DMPP and PIADIN were able to significantly reduce the emissions of CO2 and N2O compared to the control treatment when applied as biogas residues and acidified biogas residues. DCD reduced CO2 and N2O emissions in clay and loam soil. DMPP and PIADIN reduced N2O emissions in sandy soil. ENTEC increased N2O emissions in clay, loam and sandy soils. The NIs, MgCl2 amendment and acidification of biogas residues are useful to increase fertilizer use efficiency and to mitigate CO2 and N2O emissions. If the soil contains more clay, DCD is more efficient. If the soil contains more sand, strong inhibition occurs with DMPP. It was demonstrated in the present study that efficacy of nitrification inhibitors strongly depends on soil texture.

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