Quantifying the yield gap in wheat–maize cropping systems of the Hebei Plain, China

Wheat–maize double cropping is the most important cropping system on the Hebei Plain and is one of the most important cropping systems in China. In a scenario of greater food demand, and increasing water and rural labour scarcity, it is critical that the annual productivity of the system is improved in water-energy-cost efficient and low carbon ways. Based on farm surveys, this paper benchmarked the performance of wheat–maize double crops on the Hebei Plain during the 2004–2005 season. These farm yields were assessed both against experimental yields collected from on-farm maximum yield trials conducted during the same 2004–2005 season and relative to simulated estimates of the climate-driven potential productivity of the region.The survey of 362 farms in six counties of the Hebei Plain during the 2004–2005 season found wheat yields ranging from 3375 kg ha−1 to 9000 kg ha−1 with an overall average yield of 6556 kg ha−1. Maize yields averaged 7549 kg ha−1 and ranged from 3375 kg ha−1 to 11,250 kg ha−1. The aggregate production for the wheat–maize double crops grown in the 2004–2005 season averaged 14,105 kg ha−1 across the six counties. This was 72% of the average production (19,586 kg ha−1) recorded from on-farm trials conducted in each of the six counties and 60% of the simulated average production potential (24,147 kg ha−1) for the Hebei Plain in the 2004–2005 season. Thus, the annual productivity of the current cropping system could be increased with currently available technologies by 28%, while a yield increase of 42% is possible if farm yields approach the simulated yield potential.Based on farmer interviews and field observations, a number of real and perceived reasons for the current yield gaps in farmers’ fields were recognised. For instance, irrigation at stem-elongation of wheat is a current recommendation, yet only a proportion of the surveyed farmers were able to follow this strategy due to lack of access to shared irrigation facilities. Improving the region's infrastructure to enable more timely irrigation of crops will be a necessary prerequisite to improved productivity.The results from the farm surveys and on-farm trials indicate that, with current recommended practices, farmers can improve their annual farm productivity and close the current yield gaps. However, the survey identified that increasing system performance and efficiency will require a focus on both agronomic and socio-economic issues.