Spatial and Temporal Patterns of Maize Phenology in China From 2001 to 2020.

Climate change has significantly altered crop phenology, which has further impacted crop growth and yield. Accurate monitoring of crop phenology is essential for managing agricultural production in response. However, regional monitoring requires high spatial resolution distribution data, as medium resolution data suffers from mixed pixel issues. This study based on a long‐term high spatiotemporal resolution fusion data set of Normalized Difference Vegetation Index and an annually updated maize distribution data set, used the relative threshold method to identify the maize phenology in 22 provinces of China from 2001 to 2020. We further analyzed the trend of maize phenology and assessed its responses to climate change. The results reveal large inter‐annual fluctuations and spatial variability in maize phenology from 2001 to 2020. The length of the growth season (LOS) of spring maize has prolonged by 4.28 days in the northern maize zone and has shortened by 4.90 days in the southern maize zone. Additionally, the LOS of summer maize in the Huang‐Huai‐Hai region has shortened by 2.24 days. We also found a positive correlation between the length of the vegetative growth stage and the mean temperature and a negative correlation between the length of the reproductive growth stage and accumulated precipitation. This study utilized large‐scale, high‐resolution maize phenology data to analyze the trend of maize phenology and its response to climate change. These findings are expected to provide valuable support for assessing maize growth status and developing agricultural adaptive practices. Plain Language Summary: In recent years, climate change has had a notable impact on the crop phenology, influencing both crop growth and yield. It is crucial to accurately monitor when they grow and harvest to manage agricultural production in response to climate variations. This study used a comprehensive data set combining high spatial and temporal resolution imagery to retrieve the growth stage of maize in 22 provinces of China from 2001 to 2020. We found that maize grew differently across China during this period. The length of the growth season for maize got longer in the northern China and got shorter in the central and southern China. We also found that temperature mainly affected the length of the vegetative growth stage, while rainfall mainly affected the length of the reproductive growth stage. Understanding these changes can help farmers understand how maize is growing and adapt their farming practices to climate change. Key Points: We identified the length of growing season (LOS), vegetative growth stage (VGS) and reproductive growth stage (RGS) of maize in ChinaThe LOS of maize prolonged in northern China and shortened in southern China and the Huang‐Huai‐Hai regionPositive correlation between the length of VGS and temperature, while negative correlation between the length of RGS and precipitation [ABSTRACT FROM AUTHOR]