Global Maize Project in China: Dahe, Shijiazhuang, Hebei Province

This long-term field experiment was initiated in 2009 in the Dahe Experimental Station, Shijiazhuang, Hebei Province, where double cropping of summer maize in rotation with winter wheat is the main cropping system. The main plot had two treatments at this site: ecological intensification (EI) treatment with applications of 182 kg N, 107 kg P₂O₅ and 86 kg K₂O/ha in winter wheat and 182 kg N, 73 kg P₂O₅ and 70 kg K₂O/ha in summer maize; farmers’ practice (FP) treatment with applications of 225 kg N, 120 kg P₂O₅ and 55 kg K₂O/ha in winter wheat and 225 kg N, 120 kg P₂O₅ and 50 kg K₂O/ha in summer maize. Three subplots were included: N applied in all three years (N all yr), N applied in two out of every three years (N 2/3 yr), and no N applied (N 0 yr). Winter wheat (the eighth successive crop) was planted on October 5th, 2012 and harvested on June 19th, 2013, while summer maize (the ninth successive crop) was planted in the same plots on June 20, 2013 and harvested on October 4, 2013.

The EI treatment produced higher grain yields (13.8 t/ha) than the FP treatment (12.9 t/ha) in winter wheat, although less N was applied in EI treatment. Therefore, the agronomic N efficiency (kg grain yield increase per kg N applied) was higher in the EI treatment (12.8 kg/kg) than in the FP treatment (9.1 kg/kg). Similarly, partial factor productivity of N (kg grain yield per N applied) was considerably higher in the EI treatment (34.5 kg/kg) than in the FP treatment (26.0 kg/kg). For summer maize, no significant difference in grain yields was found between EI and FP treatments, although more N and P were applied in FP.