Epsilon Archive for Student Projects

Abstract

Drained peatlands used for agricultural purposes become greenhouse gas emission hotspots by accelerating the decomposition of organic matter. Nitrous oxide (N2O) emissions from fertilized peat soils are strongly influenced by soil moisture dynamics; however, the extent to which clay addition modifies the effectiveness of carbon and nitrogen (C/N) amendments (C:woodchips, biochar and N:fertilizer) in mitigating these emissions remains poorly understood. This study investigated the individual and interactive effects of clay addition and C/N amendments on N2O emissions from grassland peat soils under fertilization and simulated precipitation. A six-week controlled lysimeter experiment was conducted using 18 intact peat soil cores. Natural and clay-amended peat soils received no amendments, woodchips, or biochar, with three replicates per treatment. All lysimeters received calcium ammonium nitrate fertilizer and were subjected to three simulated rainfall events. Nitrous oxide emissions were measured using a closed static chamber technique and analyzed using a linear mixed-effects model. The linear mixed-effects analysis showed significant temporal variability in N2O fluxes throughout the experimental period (F₂₄ = 2.37, p < 0.05). However, the main effect of amendment type (Control, Biochar and Woodchip) was not significant (F₂ = 0.58, p = 0.57) and there was no significant main effect of soil type (natural versus clay-treated peat; F₁ = 0.36, p = 0.55). Furthermore, no significant amendment × soil type interaction was detected (F₂ = 1.36, p = 0.28), indicating that the effects of amendments did not differ significantly between natural and clay-treated peat soils. Despite the absence of significant treatment effects, descriptive comparisons showed lower cumulative N2O emissions following amendment application. In natural peat soil, biochar and woodchips reduced cumulative N2O emissions by approximately 42% and 47%, respectively, compared to the control. In clay-treated peat soil, wood chips reduced cumulative N2O emissions by approximately 39%, whereas biochar did not show a comparable reduction; instead, it resulted in a 9.6% increase relative to the control. These patterns suggest that C/N amendments have the potential to mitigate N2O emissions from peat soil. In conclusion, the results suggest that changes in soil moisture caused by precipitation may act as an important trigger for short-term N2O pulses in fertilized peat soils. Although wood chips and biochar exhibited lower N2O emissions than corresponding controls in several treatment comparisons, these differences should be interpreted with caution due to limited replication (n = 3 per treatment) and the absence of significant overall amendment effects in the mixed-effects model. The findings highlight the importance of considering interactions between amendment properties, soil conditions, and soil moisture dynamics when developing N2O mitigation strategies for cultivated peat soils. Long term field studies are needed to evaluate the persistence, and practical relevance of these potential mitigation effects under natural conditions.