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.

A comparison of riparian buffer designs incorporating short‐rotation Salix viminalis to mitigate surface water pollution in the Dunk River watershed on Prince Edward Island

“…Recent field studies on PEI demonstrated that cultivating shrub willow in expanded riparian buffers downslope of potato fields can significantly mitigate N 2 O emissions while increasing the effective riparian buffer width to 30 m (Wilts et al, 2022). Since REMM is unable to model soil N 2 O emissions, our study was unable to evaluate the effect of various buffer width and vegetation types on greenhouse gas mitigation.…”

“…Recent research on PEI found that cultivating shrub willow in agricultural-riparian transition areas downslope of potato fields can mitigate N 2 O emissions (by up to 90%), while increasing the effective riparian buffer width to 30 m (Wilts et al, 2022). This increased width would presumably improve stream protection from diffuse pollutants.…”

“…Furthermore, Salix cultivation produces a biomass crop that sequesters carbon and can provide a sustainable, renewable source of heat generation to offset fossil fuel use. Benefit–cost analysis revealed that such a system on PEI could be economically profitable when biomass yields exceed 5.6 ODT ha −1 year −1 (which is feasible on PEI) and harvested wood chips were used for on‐farm heat generation (Wilts et al, n.d.). This study also found that water availability was a major limiting factor on shrub willow aboveground biomass production, and thus economic viability, on PEI.…”