Nitrogen transformations in soil under plastic film mulching

Aims Plastic film mulching induces significant shifts in soil temperature and water balance, thereby influencing microbial activities, particularly those associated with nitrogen (N) transformations. However, its effects on interactions between N fate and soil N transformations remain unclear. Methods We investigated the complex interplay of soil N transformation processes using a 15 N tracing method, N availability, and N fate under plastic film mulched ridges (PFM), in contrast to a non-mulched flat system (control). Results PFM resulted in 20–28% reduction in gross N mineralization and nitrification rates and increased rates of gross microbial N immobilization. Maize showed a 19% increase in N uptake and a 127% increase in N accumulation in the PFM-treated soil (up to 80 cm depth) compared to the control. PFM effectively inhibited N leaching, while also reducing N 2 O and NH 3 gas emissions (by 32 kg N ha -1 ). In the early stages of maize growth, PFM-treated soil showed increased N availability due to accelerated rates of gross N mineralization and nitrification, which in turn bolstered N uptake by both maize and microorganisms. Furthermore, PFM effectively mitigated gaseous N emissions and N leaching, contributing to increased soil N retention and N use efficiency. As the rates of gross N mineralization and nitrification declined in the later stages of maize growth, PFM maintained substantial N availability. This was achieved by limiting NO 3 - leaching and microbial N immobilization, resulting in heightened N uptake and increased maize yield. Conclusion Plastic film mulching produced changes in soil N transformation processes that included gross N mineralization, nitrification, and immobilization rates. These changes manifested in increased N availability, maize N uptake, soil N retention, and reduced N losses.