Toward climate-smart irrigation: evaluating the sustainability of negative pressure systems through carbon-nitrogen footprint and cost-benefit analysis

In protected agriculture, irrigation methods and input structures play a critical role in shaping carbon and nitrogen footprints as well as ecological-economic performance. Using a life cycle assessment (LCA) approach, this study systematically evaluated the carbon footprint (CF), nitrogen footprint (NF), environmental damage cost (EDC), and net ecosystem economic benefit (NEEB) under conventional surface irrigation (CK) and three negative-pressure irrigation (NPI) treatments (N1, N2, N3). Compared with CK, NPI significantly reduced CF and NF by up to 74.09% and 76.45%, respectively, primarily due to reduced N2O emissions and fertilizer inputs. NPI also alleviated soil organic carbon loss by 78.85%, underscoring its strong potential for environmental sustainability. However, the high cost of ceramic emitters (accounting for 88.36%~89.80% of Costagricultural input ) and their substantial upstream emissions resulted in a significantly lower net economic benefit (NEB) for NPI compared with CK. Despite this drawback, NPI treatments demonstrated superior ecological-economic efficiency: EDC was reduced by over 85%, and the N1 treatment achieved a NEEB of -10.37 CNY ha-1, nearly reaching break-even. These results highlight a clear trade-off between environmental benefits and economic feasibility. Policy support (e.g., subsidies, carbon credits) and innovations in emitter materials (e.g., low-carbon or biodegradable alternatives) are essential to improve the overall sustainability and scalability of NPI systems.