Cultivating Salix Viminalis in Agricultural-Riparian Transition Areas to Mitigate Agriculturally Derived N2O Emissions from Potato Cropping Systems on Prince Edward Island

Abstract

Cultivating shrub willow (Salix viminalis) in agricultural-riparian transition areas has been proposed as a strategy for mitigating elevated riparian nitrous oxide (N2O) emissions in agricultural regions. Nitrogen-based fertilizers are water soluble, enter riparian areas through surface runoff and subsurface lateral flow, and are converted to N2O by incomplete anaerobic denitrification. Salix buffer strips can intercept and recycle fertilizer nitrate (NO3−) into their biomass and/or promote complete denitrification, reducing N2O emissions. We investigated the impact of Salix viminalis buffers on N2O emissions relative to grassed buffers and upslope cultivated fields in potato rotations at 5 research sites across Prince Edward Island (PEI), Canada. Greenhouse gas (N2O, CO2, CH4) flux at the soil-atmosphere interface was measured using non-steady-state static chambers in 2018 and 2019. NO3− exposure, soil temperature, and soil moisture content were quantified. Agricultural-riparian Salix significantly reduced N2O emissions even when high NO3− inputs occurred and following precipitation events. Mean cumulative seasonal reductions of 1.32 kg N2O–N ha−1 (− 0.02 to 6.16 kg N2O–N ha−1) were observed in Salix relative to cultivated fields; however, they were not significantly different than grass. The mean cumulative average global warming potential of Salix was 613 kg CO2e ha−1 lower than cultivated fields, with reductions of up to 2918 kg CO2e ha−1. Differences in N2O flux between vegetation types were the greatest influencing factor. No hot moments of N2O emission were observed in Salix following high rainfall events, which coincided with up to 95% decreases in N2O emissions in Salix relative to cultivated fields.