Mitigation of nitrous oxide emissions from an acidic soil by valorization of industrial waste

Increasing evidence suggests that alkaline mineral amendments from industrial wastes (e.g., phosphorus tailing, PT) have potential to ameliorate soil acidification and improve agriculture sustainability. However, the effects of such amendment on nitrous oxide (N₂O) production remain elusive. To fill this knowledge gap, an incubation experiments were conducted with an acidic soil of pH 4.80 treated with i) control (CK, no amendments), ii) urea at 60 mg N kg^-1 (U), iii) 10 g kg^-1 amendments (S) and iv) 10 g kg^-1 amendments plus urea at 60 mg N kg^-1 (S+U). A 184-h experiment was conducted with a robotized incubation system for monitoring real-time gases (O₂, N₂O, N₂, CO₂) dynamics. Results from this batch experiment showed that the soil pH was significantly increased with the amendment addition (S and S+U) from 4.80 to above 6.00. Meanwhile, the mineralization, nitrification and denitrification processes were stimulated with the amendment addition. The N₂O production was reduced by an average of 65.7% with the amendment addition compared to that without the amendment application. After incubation, higher N₂ productions were observed from the soil with amendment addition (S and S+U) than untreated soil (P<0.05). The findings suggest that the N₂O emissions from acidic soils can be considerably controlled by valorization of PT.