Purpose: Nitrous oxide (N2O) and methane (CH4) are some of the most important greenhouse gases of the 21st century. Vegetated riparian buffers are primarily implemented for their water quality functions in agroecosystems and their location in the agricultural landscape allows them to intercept and process pollutants from immediately adjacent agricultural land. They recycle increase soil carbon (C), intercept nitrogen (N)-rich runoff from adjacent croplands, and are seasonally anoxic, promoting processes producing environmentally harmful gases including N2O and CH4. Against this context, the study quantified these atmospheric losses between a cropland and vegetated riparian buffers that serve it.
Methods: We used the static chamber to measure N2O and CH4 emissions simultaneously with soil. Gas measurements were done simulataneously with soil and environmental variables for a 6-month period in a replicated plot-scale facility comprising of maize cropping served by three vegetated riparian buffers, namely: (i) a novel grass riparian buffer; (ii) a willow riparian buffer, and; (iii) a woodland riparian buffer. These buffered treatments were compared with a no-buffer control.
Results: The no-buffer control generated the largest cumulative N2O emissions of 18 929 g ha-1 (95% confidence intervals: 524.1 - 63 643) whilst the maize crop upslope generated the largest cumulative CH4 emissions of 5 050 ± 875 g 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..
Conclusions: Our results suggest that maize production in general, and situations where such cropping is not undertaken in tandem with a riparian buffer strip, result in atmospheric CH4 and N2O concerns.