Net ecosystem carbon budget, net global warming potential and greenhouse gas intensity in intensive vegetable ecosystems in China

Abstract

The net ecosystem carbon budget (NECB), global warming potential (GWP) and greenhouse gas intensity (GHGI) of vegetable ecosystems are not well documented. The net GWP and GHGI either including the carbon emissions from agricultural management (net mGWP/mGHGI) or not were estimated from an intensive vegetable production system in Nanjing, China between 2009 and 2010. The four typical consecutive rotations included celery–tung choy–baby bok choy–amaranth (C–T–Bb–A), choy sum–celery–tung choy–bok choy (Cs–C–T–Bc), garland chrysanthemum–tung choy–bok choy (G–T–Bc), and celery–choy sum–lettuce–bok choy (C–Cs–L–Bc). A net sink was observed and estimated at crop seasonal time scale for both the NECB and the soil organic carbon change (δSOC) from the four vegetable rotation fields. The mGWP, net GWP, net mGWP, GHGI and mGHGI all showed nearly consistent changes among the rotations and among the vegetables within each rotation. The global warming potential ranged from 26MgCO2equiv.ha−1 to 109MgCO2equiv.ha−1 for net GWP and 36MgCO2equiv.ha−1 to 131MgCO2equiv.ha−1 for mGWP. The GHGI and mGHGI ranged from 0.17kgCO2equiv.kg−1vegetable to 0.41kgCO2equiv.kg−1vegetable and from 0.22kgCO2equiv.kg−1vegetable to 0.49kgCO2equiv.kg−1vegetable, respectively. The mGWP, net GWP, net mGWP, GHGI and mGHGI were dominated by the GWP resulting from N2O emissions. Annual cumulative direct N2O emissions were 374kgN2Oha−1 for G–T–Bc, 216kgN2Oha−1 for C–T–Bb–A, 159kgN2Oha−1 for Cs–C–T–Bc and 89kgN2Oha−1 for C–Cs–L–Bc, respectively. High N fertilizer input was likely responsible for the high N2O emissions. Increasing fertilizer use efficiency and adoption of best practices are effective measures for sustainable intensive vegetable production.