RESUMO
Introduction: Drip irrigation under mulch film promotes a non-uniform salinity distribution in salt fields. The effect of different N application methods on the growth and yield of cotton under drip irrigation under mulch film conditions in eastern coastal saline-alkaline soils in China remain remained unclear. Methods: A randomized complete block design was used in the experiment. Three N application methods were assigned: N applied under mulch film (low-salinity area; UM), N applied between mulch films (high-salinity area; BM), and half N applied under mulch film and half between mulch films (HUHB). Results: Plant height, photosynthesis, Chl content, boll load, biomass, boll weight and boll density under UM were all significantly higher than those under the other two treatments. The N absorption of UM was higher than in the other two treatments, which might be attributed to the expression of GHNRT1.5 and GHNRT2.1. The net NO3- influx in the roots in UM increased significantly compared with that in BM. The yield and FNRE of UM were 3.9% and 9.1%, respectively, and were 26.52% and 90.36% higher than under HUHB and BM treatments. Discussion: UM not only improved cotton yield but also alleviated the pollution of N residue on drip irrigation under mulch film conditions in salt areas.