Optimizing nitrogen management to achieve high yield, high nitrogen efficiency and low nitrogen emission in winter...

Achieving both high yield and high nitrogen (N) use efficiency (NUE) simultaneously is a current research hotspot in crop production. To investigate approaches for achieving high yield and NUE, field experiments using N fertilizer rates of 0, 120, 180, 240, 300 and 360 kg N ha^-1 were conducted to study relationships between yield, N uptake and N efficiency during three wheat growing seasons from 2013 to 2016 in three experimental sites (Shangshui, Kaifeng and Wenxian) in the Huang-Huai Plain. Yield, biomass and N concentrations of plants and soil were determined. The results indicated that increased N application would affect soil N residue and increase N₂O emission, suitable N application rate (N240-N268) contributed to maintaining soil fertility and reducing N₂O emission for achieving high yield, high NUE and low N₂O emission. High plant N accumulation (PNA) during jointing to anthesis had the best correlation coefficient with yield and NUE compared to other growth stages, which contributed to achieving high yield and NUE simultaneously. The dry matter produced by a unit of N was defined as N productivity, such as plant N net phase productivity (PNPn) and leaf N productivity (LNP). High PNPn during jointing to anthesis was significantly related to both yield and NUE. The LNP indicator (i.e. photosynthetic N use efficiency, PNUE) in the flag showed significant correlation with both yield and NUE after booting under high PNA levels. These results suggest that PNPn and PNUE could combine high yield and high NUE under high PNA conditions. Besides, to match soil N supply to plant N demand, optimum soil nitrate N accumulation and alkali-hydrolysable N (AHN) content ranges were determined. This study provides a theoretical basis to achieve high yield, high NUE and low N₂O emission for N management in wheat field production.