Impact of drainage type on simultaneous nitrogen losses in Atlantic Canada

Abstract

Nitrogen (N) losses from agricultural tile drainage systems are environmental and economic losses for producers. This field study quantified N losses from three reps of shallow (SD), deep/conventional (DD), and controlled drainage (CD) on farmland in Nova Scotia. Drainage systems were under corn and alfalfa–oats–clover production. Outflow water and gas samples were obtained and analyzed for nitrate and nitrous oxide. Nitrate-N loads were 5.0, 11.1, and 6.4 kg ha−1 in 2015; 1.8, 6.7, and 2.8 kg ha−1 in 2016; and 0.74, 1.8, and 1.6 kg ha−1 in 2017 for SD, DD, and CD, respectively. Controlled drainage reduced NO3−-N loading by 42.3%–58.2% when compared with the conventional/DD in 2 of 3 yr of study, whereas SD was found to reduce NO3−-N loading by 54.9%–73.1% compared with DD in all years studied. Total NO3−-N losses in this study were measured during the growing season (1 Apr. to 31 Oct.); the magnitude of NO3−-N losses and treatment effects may vary if studied year-round. Nitrous oxide fluxes were variable and low in magnitude throughout the study. Cumulated N2O losses were <1% of the applied N for all drainage types. Controlled drainage increased yields compared with SD and DD. The use of CD in the region could aid in reducing climate stresses, as well as overall NO3−-N loads exiting drainage systems and may enhance crop yields compared with conventional systems. Future studies on dissolved N2O losses from drainage water may provide important insight into whether dissolved N2O losses exceed surface emissions.