Nitrogen use efficiency was increased by manure combined with plastic film mulching

A better understanding of the fate of nitrogen (N) fertilizer is critical for designing appropriate N management and for evaluating the total N use efficiency under plastic mulching on farmland. A two-year field experiment was conducted to determine the effects of manure and plastic mulching on the fate of 15 N-labelled urea. Urea was applied at the same rate to spring maize (Zea mays L.) growing in soils under three different treatments (no film mulching + mineral fertilizer, CK; film mulching + mineral fertilizer, FN; and film mulching + mineral fertilizer + cow manure, FNM) in 2018 and 2019, but 15 N-labelled urea was applied in 2018 only. FN and FNM increased the maize grain yields for both years. FN increased the total N uptake in the aboveground biomass by 20% in 2018, whereas no significant difference in 15 N uptake was observed in 2018 compared with that of the CK. The residual 15 N in the 0–1 m soil layer fell within a range of 8–20% two years later and was mostly retained in the top 0.2 m. FN and FNM significantly increased the total N uptake after two years, while the opposite trend was observed for potential N loss. The decreases in potential loss were 6% under FN and 39% under FNM. Therefore, our results indicate that plastic film mulching combined with manure application could not only increase maize grain yields and N uptake but also reduce the loss of fertilizer N, affecting the fate of urea-N in maize production.