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

The long-term field experiment of the Global Maize Project was initiated in 2009 in Dahe station, Shijiazhuang city, Hebei Province. Summer maize and winter wheat rotation is the dominant cropping system in Hebei. Winter wheat (the 14th successive crop) was planted in October 2015 and was harvested in June 2016. Summer maize (the 15th successive crop) was planted in June 2016 and harvested in September 2016. Two fertilizer application treatments, the ecological intensification (EI) and the farmers’ practice (FP), were used to evaluate the grain yield and nitrogen (N) use efficiency in the experiment. The nutrient application rates in the EI treatment were 182-73-70 and 182-107-86 N-P₂O₅-K₂O kg/ha for summer maize and winter wheat. The corresponding rates for the FP were 225-120-50 kg/ha for both summer maize and winter wheat. The study also had three subplots that created three different N application regimes: (1) N applied in all three years, (2) N applied in two of every three years, and (3) no N applied in any year.

For summer maize, the average grain yield in the EI treatment receiving N in all years was 7.1 t/ha, and was higher than the similar treatment in FP (6.0 t/ha). The grain yield produced by the two other subplots of the EI treatment were 6.5 t/ha and 3.9 t/ha, respectively. The corresponding grain yields in the FP treatment were 6.3 t/ha and 3.9 t/ha. We calculated the agronomic efficiency (AE) and partial factor productivity (PFP) of N and the EI had a much higher AE and PFP value (17.3 kg/kg and 38.9 kg/kg) compared to FP (9.1 kg/kg and 26.7 kg/kg). Even though the subplot where N was applied in two of every three years of EI treatment did not produce as much grain yield as N applied in all years, this subplot still had a higher AE and PFP value (14.2 kg/kg and 35.9 kg/kg) than the same subplot in the FP treatment (10.5 kg/kg and 28.0 kg/kg).

For winter wheat, EI treatment with N application in all years produced 7.0 t/ha grain yield, which was lower compared to FP treatment (8.1 t/ha). There was no significant difference for either the AE and the PFP value found between the EI (19.9 kg/kg and 38.4 kg/kg) and the FP treatment (19.1 kg/kg and 36.2 kg/kg). This could be due to the lower grain yield and similarly lower fertilizer input in the EI treatment. Unstable weather conditions, especially the uncertainty of precipitation in the growth period of winter wheat should be acknowledged. The positive effects of long-term balanced fertilization on grain yield and the higher nutrient use efficiencies of the cropping system justifies continued innovation in ecological and sustainable system maintenance.