The Potential of Carbon Sequestration and N₂O Emissions Due to Different Sward Ages after Grassland Re-Sowing

The Potential of Carbon Sequestration and N₂O Emissions Due to Different Sward Ages after Grassland Re-Sowing

In order to quantify carbon (C) sequestration and nitrous oxide (N₂O) emission rates from grassland of different sward ages (2, 5 and 18 years) after grassland re-establishment, a 2-year field experiment was conducted on a sandy loam in 2010/2011 (2011/2012). The trial was set up in a randomized plot experiment with three replicates including a control (no N-fertilizer) and a fertilized treatment (240 kg N/ha/year as cattle slurry). N₂O emissions were measured on a weekly basis using the closed chamber method. The soil carbon content was measured twice a year from soil cores. Results showed a lower soil carbon content (0 - 30 cm) in the 2-year-old sward (63.7 t C/ha) compared to the 5-year-old (72.8 t C/ha) and 18- year-old sward (77.1 t C/ha) (P ≤ 0.05). No significant relationship could be found between the cumulative N₂O emissions per year and sward age. On average, the 18 years-old fertilized grassland showed the highest N₂O emissions compared to all other treatments in both experimental years (2.56 kg N₂O-N/ha in 2010/11 and 1.17 kg N₂O-N/ha in 2011/12).Grassland renovation leads to a decay of soil C. In our experiment, this effect was compensated within five years of grassland re-establishment (P ≤ 0.05). On average, the N₂O emissions were low in younger swards compared to old grassland (n.s.).