Winter wheat yield potentials and yield gaps in the North China Plain

The North China Plain (NCP) is the most important wheat production area in China, producing about two-thirds of China's total wheat output. To meet the associated increase in China's food demand with the expected growth in its already large population of 1.3 billion and diet changes, wheat production in the NCP needs to increase. Because of the farmland reduction due to urbanization, strategies for increasing wheat production in the NCP should be targeted at increasing current yields. To identify options for increasing wheat yields, we analyzed the yield potentials and yield gaps using the EPIC (Environment Policy Integrated Climate) model, Kriging interpolation techniques, GIS and average farm yields at county level. As most (ca. 82%) of the winter wheat in the NCP is irrigated, it is justified to use potential yield as the benchmark of the yield gap assessment. Wheat potential yields simulated with EPIC using daily weather data from 1960 to 2007 at 43 representative sites varied from 6.6 to 9.1 t ha−1 in the NCP, generally increasing from north to south associated with decreasing low temperature stress. Based on the county-level data (2004–2007), the actual wheat yield varied between 2.4 and 7.7 t ha−1, while the yield gap was between 0.6 and 5.3 t ha−1 (7–69% of the potential yield) across the NCP and decreased with increase of actual yields (R2 = 0.82). For the entire region, the weighted average actual yield was 5.7 t ha−1, while the yield gap was 2.7 t ha−1 or 32% of the potential yield. Using 80% of the potential yield as an exploitable level, the average actual wheat yield in the NCP could be increased by 1.0 t ha−1 or 18%. The results provide an indication of the possibilities to increase wheat yields in the NCP.