Influence of seasonal climate and water table management on corn yield and nitrous oxide emissions

Compared to regular tile drainage (FD), controlled drainage systems with sub-irrigation (CDS) can increase crop yield but could potentially heighten the production and subsequent emission of nitrous oxide (N2O). Accounting for growing season rainfall categorized under wet, dry and normal, the long-term effects of CDS on crop yield and nitrous oxide (N2O) emissions were investigated at a commercial corn farm in southwestern Quebec. Based on yield data collected over 12 years at the study site, CDS improved grain yield compared to regular tile drainage (FD), depending on the quantity and temporal distribution of rainfall during the growing season. On average, CDS positively affected grain yield by 17.7% and 3.4% in dry and normal years, but reduced yield by 25% in a wet year. The lower yield under CDS was particularly observed when excessive monthly rainfall (230 mm) occurred during the crop's vegetative period. In three of six years, N2O fluxes under CDS treatments were greater by 49% than those under FD but 45% lower in the remaining years, implying that - notwithstanding the quantity of growing season rainfall - CDS does not necessarily always produce greater fluxes than FD. N2O fluxes coincided more with fertilizer application, particularly when associated with a rainfall event. Given that CDS tends to increase crop yield and does not heighten N2O emissions, it remains a beneficial management practice to be adopted in subsurface drained croplands, where appropriate.