Improving potential of reactive nitrogen and carbon footprint of intensified greenhouse cucumber-tomato production with optimized drip irrigation with nitrogen reduction strategies

Guaranteeing a robust supply of vegetables is a significant public welfare endeavor. However, the imple-mentation of irrational water and fertilizer regimes in greenhouse vegetable fields (GVF) has resulted in adverse environmental impacts. Therefore, it is crucial to develop water and fertilizer regimes to maintain the produc-tivity of greenhouse vegetables with less carbon (C) and reactive nitrogen (Nr) footprint. A four growing seasons experiment involving the cultivation of cucumbers and tomatoes was conducted in the suburbs of Beijing. The experiment comprised three treatments: flood irrigation with a conventional urea-N application (FN), drip fer-tigation with a conventional urea-N application (DN), and drip fertigation with a 50% reduction of urea-N application (DRN). The results showed that about 70% of annual N inputs in GVF were surplus, posing a high risk of loss. For the FN treatment, the N budget, Nr loss, Nr footprint per unit of vegetable yield (NrFY), Nr footprint per unit of net return (NrFR), greenhouse gas (GHG) emissions, C footprint per unit of vegetable yield (CFY), C footprint per unit of net return (CFR) were respectively quantified as follows: 1653 kg N ha- 1 yr- 1, 776 kg N ha- 1 yr- 1, 4.39 kg N t-1 yr-1, 24.48 kg N yen 10000-1 yr-1, 46548 kg CO2-eq ha- 1 yr- 1, 262.98 kg CO2-eq t-1 yr- 1 and 1467.58 kg CO2-eq yen 10000-1 yr-1. Compared with FN, DN significantly reduced Nr loss (25%), NrFY (24%), NrFR (22%), GHG emissions (6%), CFY (4%), while it increased N surplus (9.7%) and produced lower farmers' net return ( yen 13486 ha- 1 yr-1). Concurrently, DRN significantly reduced the N surplus, Nr loss, NrFY and NrFR by-35%, decreased the GHG emissions, CFY and CFR by-20%, and improved farmers' net return by yen 674 ha- 1 yr- 1 compared to FN treatment. Therefore, this study highlighted that an integrated water and fertilizer regulation strategy (drip irrigation replacing flood irrigation coupled with a 50% reduction in chemical N application) can simultaneously achieve environmental and economic benefits in the context of high N inputs. This contributes to the sustainable development of intensive vegetable cultivation systems.