The potential of carbon sequestration and N20 emissions due to different sward ages after grassland re-sowing

摘要

In order to quantify carbon (C) sequestration and nitrous oxide (N_2O) emission rates from grassland of different sward ages (2, 5 and 18 years) after grassland rc-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-fcrtilizer) and a fertilized treatment (240 kg N/ha/ycaras cattle slurry). N_2O 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 N_2O emissions per year and sward age. On average, the 18 years-old fertilized grassland showed the highest N_2O emissions compared to all other treatments in both experimental years (2.56 kg N_2O-N/ha in 2010/11 and 1.17 kg N_2O-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-cstablishment (P=<0.05). On average, the N_2O emissions were low in younger swards compared to old grassland (n.s.).