China’s nitrogen management of wheat production needs more than high nitrogen use efficiency

Abstract

Nitrogen (N) fertilizer is essential for increasing yields in intensive agricultural systems, but it also creates an environmental burden. Improving recovery efficiency of N (REN) is the key to balancing the trade-off between crop production and environmental protection. However, the current status of the REN in China and whether a high REN is sufficient for sustainable wheat production remain unclear. Here we estimated the REN of wheat production in China using N-difference method and 15N-labelled method, explored strategies to improve REN, and clarified that China’s nitrogen management of wheat production needs more than high nitrogen use efficiency. The findings of a 12-year field trial showed that the REN estimated by N-difference method was double that estimated by 15N-labelled method, and meta-analysis results showed that the national mean REN estimated by the two methods were similar, ranging from 30% to 33%. Notably, the REN was consistently lower than the global mean according to both methods; thus, exploring strategies to improve REN is vital. Results showed that reducing N fertilizer application rate and N surplus are essential for improving REN; however, indiscriminately reducing N application rate creates a great risk of reducing yields since insufficient and excessive use of N fertilizer is prevalent in wheat production of many counties. The establishment of the inherent interconnections among REN, crop yield, and N surplus showed that REN or N surplus should be used together with yield as an indicator of the sustainability of crop systems. The implementation of comprehensive N management techniques increased REN (38–104%) and yield (8–9%) while reducing N surplus (52–89%), which provides a good starting point for further discussions of N fertilizer management for sustainable wheat production.