Changes in Hydrothermal Conditions During the Spring Maize Growth Period in Inner Mongolia from 1961 to 2020 and Their Impact on the Meteorological Yield

Climate change has led to significant changes in water and heat conditions in crop production areas, which have in turn affected the spring maize growth and yield. This study analyzed the spatiotemporal variation characteristics of the water and heat conditions, such as the growth degree-day (GDD), killing degree-day (KDD), sunshine hours (SD), effective precipitation (Pe), and irrigation water requirement (IR), of spring maize in Inner Mongolia based on data from 50 meteorological stations. The relationship between hydrothermal conditions and yield was revealed using methods that included stepwise regression analysis. The results showed that the GDD during the spring maize growth period ranged from 513 to 2011 degrees C, with high-value areas concentrated in western and southeastern regions of Inner Mongolia. The GDD showed an increasing trend during all the growth periods. High-KDD areas were mainly distributed in the Alxa League region in western Inner Mongolia, and the KDD showed an increasing trend during all periods except the rapid fertility period. The spatial distribution of the SD was consistent with that of the GDD, and the SD values for each reproductive period showed a decreasing trend. The average Pe and IR values in the last 60 years were 111 mm and 386 mm, respectively, and showed opposite spatial distribution trends. The overall Pe trend was decreasing and that of the IR was increasing, which will aggravate future water resource consumption in the region. Stepwise regression analysis showed that the Pe was the main factor affecting the spring maize yield. Overall, the spring maize fertility period in various regions of Inner Mongolia was extremely uneven in terms of the hydrothermal conditions. This study provides a basis for the regional spatial spring maize layout and the sustainable use of water and heat resources in the region.