Agro Fossil Free - Balancing high yields and low N2O emissions from greenhouse vegetable fields with large water and fertilizer input: a case study of multiple-year irrigation and nitrogen fertilizer regimes

Algemene Beschrijving

Background and aims: Greenhouse vegetable production is commonly associated with substantial nitrous oxide (N2O) emissions, low nitrogen (N)and irrigation water use efficiency (NUE and IWUE) due to excess N input and frequent flooding irrigation, so it is crucial to develop irrigation and fertilization strategies to alleviate N2O emissions while ensuring vegetable productivity. Methods: An experiment spanning three crop rotations of cucumber and celery in a greenhouse was conducted in North China Plain (NCP). It included four treatments, i.e., no N fertilizer (CK), farmers' conventional fertilization (FP), conventional fertilization rate with drip fertigation (FPD), and reduced N fertilizer rate with drip fertigation (RFPD). Results: The mean annual area-scaled, yield-scaled N2O emissions and direct N2O emission factors (EFd) of FP were 36 kg N ha−1, 175 g N t−1 and 1.3%, respectively. FPD significantly reduced N2O emissions by over 25% (both in area- and yield-scaled), enhanced IWUE by 37%, and had no significant negative effects on vegetable yield or NUE. RFPD also significantly mitigated both area- and yield-scaled N2O emissions by about 45%, improved IWUE by 40% and NUE by 25%, while maintaining vegetable yield. Quadratic curves were fitted to the boundary points of ln-transformed N2O emissions against soil temperature and water-filled pore space (WFPS), with the maximum N2O losses occurring at 19.5 ℃ or 68%. N2O emissions responded to IWUE and NUEs following an exponential (R2 = 0.71, P < 0.001) and a linear-plateau model (R2 = 0.67, P < 0.001), respectively. Conclusions: Drip irrigation with reduced N fertilizer rate is a suitable agronomic practice to simultaneously mitigate N2O emissions and improve both IWUE and NUE while maintaining vegetable yield from typical greenhouse cucumber-celery fields in NCP.