Long-term trends in grain yield and main nutrient contents of three staple cereal crops in China (1980-2024).

BACKGROUND: Rice, wheat, and maize are China's three main staple crops and key sources of dietary energy and essential nutrients. Decades of cultivar improvement and changes in field management have been accompanied by substantial increases in grain yield, while the nutrient composition of these crops may also have changed over. However, the long-term trends of these alterations are poorly understood. Characterizing these trends is crucial for safeguarding national food security and ensuring an adequate dietary nutrient supply for the Chinese population. OBJECTIVE: To systematically characterize long-term trends in the grain yield and major nutrient contents of rice, wheat, and maize in China between 1980 and 2024. Methods: Data on rice, wheat, and maize from 1980 to 2024 were collected from publicly available food composition databases and published literature databases. Linear regression models were fitted for each crop and nutrient variable to characterize temporal trends in grain yield and nutrient concentrations. RESULTS: From 1980 to 2024, grain yield overall increased in all three crops. Grain protein concentration declined significantly in rice, wheat, and maize. Fat content decreased significantly in wheat and maize, whereas no clear trend was detected for rice. Carbohydrate content decreased significantly in wheat and increased in maize; no clear trend was detected in rice. Dietary fiber content increased significantly in rice and wheat; no clear trend was detected in maize. Furthermore, grain yield was negatively associated with protein concentration across all three crops, and with fat concentration in wheat and maize, whereas yield was positively associated with dietary fiber concentration in rice and wheat. CONCLUSION: Grain yields of rice, wheat, and maize substantially increased in China from 1980 to 2024; however, long-term trends in nutrient composition differed among the three crops. These findings highlight the need to consider nutritional quality alongside yield in crop improvement and food security strategies, and provide important empirical evidence to inform food security policy and crop breeding programs. SYSTEMATIC REVIEW REGISTRATION: https://doi.org/10.17605/OSF.IO/G3CFH, Registration identifier: 10.17605/OSF.IO/G3CFH.