Integrated assessment of agronomic, environmental and ecosystem economic benefits of blending use of controlled-release and common urea in wheat production

Abstract Even though blending controlled-release urea (CRU) with and common urea (CU) has been shown as an effective strategy to improve grain yield and N use efficiency in wheat production, its environmental performance with a life cycle assessment (LCA) and ecosystem economic benefits remain unclear. To evaluate the agronomic, environmental and ecosystem economic performance of blending urea (BU), a field experiment with five N rates (0-300 kg N ha-1) and two N fertilizer sources (CU and BU) was carried out in the North China Plain from 2017 to 2019. The results demonstrated that, compared with CU, the one-time application BU before planting maintained the same high grain yield and N uptake in the optimal N treatment (170 kg N ha-1) and at higher N rates; and increased the grain yield by 12.6% in the sub-optimal N (Nsub) treatment. The LCA results revealed that BU significantly reduced the life-cycle reactive N (Nr) losses by 16-19% and the N footprint by 14-25%, which were mainly attributed to the reduced N losses through ammonia volatilization (17-20%) and nitrate leaching (18%). BU increased the greenhouse gas (GHG) emission by 4% from N fertilizer production and transportation process, and significantly reduced the GHG emissions generated during the on-field N fertilizer application process by 16-35%, compared to CU. As a result, the overall GHG emission and C footprint were not significantly different between the two fertilizer sources. In contrast, BU reduced the C footprint than CU when fertilizers were applied at sub-optimal N rate. According to the ecosystem economic analysis which considered the costs of both ecosystems and human health, BU improved the ecosystem economic benefit (EEB) than CU except for the farmers’ conventional level (300 kg N ha-1). The highest EEB was achieved when BU was applied at the optimal level. In summary, application of BU at optimal N rate could not only achieve a high grain yield, but also enhance EEB meanwhile mitigating the negative environmental impacts, and therefore should be considered an effective strategy for sustainable wheat production system.