Cover crops and soil tillage differently affect N2O emissions.

The case study investigated the impact of different cover crops and tillage strategies on nitrous oxide (N2O) emissions in agricultural soils. Four cover crops were studied: perennial ryegrass (RG), plantain (PL), a combination of RG and PL (RG-PL), and a mix of RG, PL, and red clover (RG-PL-RC). These cover crops were terminated either by shallow rotovation followed by deeper ploughing (ro+plou) or directly by ploughing (plou). N2O flux was continuously measured using automated chambers from March to June 2021. The study found that cumulative N2O-N emissions were generally higher for plou compared to ro+plou, with 2-to-5-fold higher emissions observed in plou for RG-PL, RG, and PL, and the smallest difference in emissions observed for RG-PL-RC. In ro+plou, the lowest and highest cumulative N2O emissions were observed in PL and RG-PL, respectively, while in plou it was RG-PL-RC and RG-PL, respectively. The average soil nitrate (NO3-N) levels increased initially, indicating mineralization and nitrification of residue-N, but gradually decreased thereafter. This decrease in NO3-N levels corresponded with an increase in N2O emissions, suggesting denitrification as the main process of N2O production.