Soil N₂O and CH₄ emissions from fodder maize production with and without riparian buffer strips of differing...

Nitrous oxide (N₂O) and methane (CH₄) are some of the most important greenhouse gases in the atmosphere of the 21st century. Vegetated riparian buffers are primarily implemented for their water quality functions in agroecosystems. Their location in agricultural landscapes allows them to intercept and process pollutants from adjacent agricultural land. They recycle organic matter, which increases soil carbon (C), intercept nitrogen (N)-rich runoff from adjacent croplands, and are seasonally anoxic. Thus processes producing environmentally harmful gases including N₂O and CH₄ are promoted. Against this context, the study quantified atmospheric losses between a cropland and vegetated riparian buffers that serve it.

Environmental variables and simultaneous N₂O and CH₄ emissions were measured for a 6-month period in a replicated plot-scale facility comprising maize (Zea mays L.). A static chamber was used to measure gas emissions. The cropping was served by three vegetated riparian buffers, namely: (i) grass riparian buffer; (ii) willow riparian buffer and; (iii) woodland riparian buffer, which were compared with a no-buffer control.

The no-buffer control generated the largest cumulative N₂O emissions of 18.9 kg ha^- 1 (95% confidence interval: 0.5-63.6) whilst the maize crop upslope generated the largest cumulative CH₄ emissions (5.1 ± 0.88 kg ha^- 1). Soil N₂O and CH₄-based global warming potential (GWP) were lower in the willow (1223.5 ± 362.0 and 134.7 ± 74.0 kg CO₂-eq. ha^- 1 year^- 1, respectively) and woodland (1771.3 ± 800.5 and 3.4 ± 35.9 kg CO₂-eq. ha^- 1 year^- 1, respectively) riparian buffers.

Our results suggest that in maize production and where no riparian buffer vegetation is introduced for water quality purposes (no buffer control), atmospheric CH₄ and N₂O concerns may result.