Estimating Net Carbon and Greenhouse Gas Balances of Potato and Pea Crops on a Conventional Farm in Western Canada
Ningyu Quan, Sung‐Ching Lee, Chitra Chopra, Zoran Nesic, Paula Porto, Patrick K.C. Pow, Rachhpal S. Jassal, Sean Smukler, Maja Kržić, Sara Knox, T. Andrew Black
Abstract
Abstract Quantifying the emissions of the three main biogenic greenhouse gases (GHGs), carbon dioxide (CO 2 ), nitrous oxide (N 2 O) and methane (CH 4 ), from agroecosystems is crucial. In this study continuous measurements of N 2 O, and CH 4 emissions from potato and pea crops in southwest British Columbia, Canada were made using the eddy‐covariance (EC) technique. Flux footprint analysis, coupled with EC and manual nonsteady state chamber measurements, was used to address the spatial heterogeneity resulting from the field edge at the study site. Flux footprint corrections had a larger effect on N 2 O fluxes than CO 2 fluxes because of a more pronounced difference in N 2 O fluxes between the crop and edge areas. After flux footprint corrections, the potato and pea crops were both weak CO 2 sinks with annual net ecosystem exchange values of −57 ± 9 and −97 ± 16 g C m −2 yr −1 , respectively. However, after taking carbon (C) export via crop harvest and C import via seeding into account, the potato crop shifted to being a moderate C source of 284 ± 55 g C m −2 yr −1 , while the pea crop became near C neutral, sequestering only 30 ± 26 g C m −2 yr −1 . Annual GHG balances, quantified by converting N 2 O and CH 4 to CO 2 equivalents as pulse emissions using respective global warming potentials on a 100‐year timescale, were 417 ± 88 and 152 ± 106 g CO 2 e m −2 yr −1 for the potato and pea crops, respectively, with N 2 O contributing the largest proportion to annual total GHG balances and outweighing the CO 2 uptake from the atmosphere.