Climate and crop yields impacted by ENSO episodes on the North China Plain: 1956-2006

El Nino-Southern Oscillation (ENSO) contributes to climate anomalies, especially those related to regional rainfall, which affect crop production. Although the North China Plain (NCP) is the most important agricultural production region in China, the impact of ENSO events on local climate and crop production has received only limited attention. Therefore, the impact of different phases of ENSO on local climate and production of winter wheat and summer maize, both rain fed and irrigated, was investigated at three sites using the agricultural production systems simulator model. Data on daily temperature, precipitation, and sunshine hours for 50 years (1956-2006) were analysed to build climate scenarios for three categories of ENSO: years with El Nino events, years with La Nina events, and neutral years. The pattern of climate change was generally similar across the three sites: annual precipitation decreased slightly and annual mean sunshine hours decreased significantly, whereas annual mean minimum temperature increased significantly, leading to a significant increase in mean air temperature. Precipitation decreased and temperature and sunshine hours increased in both El Nino and La Nina years but remained stable in neutral years. Under full irrigation, the probability of exceeding distribution that crop yield would be higher was not markedly affected (P > 0.05), although the yields in both El Nino and La Nina years differed markedly from those in neutral years, especially in maize. Under rain-fed conditions, the yield of maize was decreased greatly (P < 0.05), the probability distribution of such reduction being the highest in La Nina years at all the sites (P < 0.05). At the provincial level, yields from well-managed fields differed (P[ 0.05) with the ENSO category: production of maize was more vulnerable than that of wheat in El Nino and La Nina years. El Nino and La Nina had similar effects on climatic variables across the NCP: low yields in El Nino and La Nina years due to lower precipitation and high yields in neutral years due to longer sunshine hours and additional irrigation.