Climate change has caused significant alterations in crop cultivation patterns and has affected crop suitability as well as its production. In this study, we investigated the changes in cultivation patterns and climate suitability of spring maize in Inner Mongolia from 1959 to 2018. We used the daily meteorological data from 50 weather stations and growth period data of spring maize from nine agrometeorological stations. In addition, the quantitative and interdecadal relationship between climate suitability of regions and climate-induced crop yield was analyzed using stepwise regression and cross wavelet transform. The results show that: (1) The planting boundaries of different spring maize maturity types extend to the north and east. In the middle part, early maturity maize has been replaced by medium maturity maize. The unsuitable planting areas in Northeast Inner Mongolia are decreasing, and the early maturity areas are increasing. (2) The climate suitability for spring maize planting areas is increasing. However, variations occur between different regions; the eastern region has the highest climate suitability (S_z = 0.67), but the overall trend is decreasing in this region. Whereas the central region has moderate suitability (S_z = 0.62), with a significantly increasing trend (p < 0.05). The western region is lower (S_z = 0.60) and the trend is not significant. (3) Climate suitability and climate-induced yields are generally positively correlated. The primary factors affecting climate-induced yields are sunshine hours, followed by climate suitability, rainfall, and temperature. The cross-wavelet transform shows that climate suitability and climate-induced yield have greater periodicity in the late growth period. Appropriate expansion of the planting range of medium-late maturity spring maize can fully adapt to the impact of climate warming. Therefore, it is necessary to study suitability trends of regions to adopt comprehensive maize production measures.

Soil water and salt transport in soil profiles and capillary rise from shallow groundwater are significant seasonal responses that help determine irrigation schedules and agricultural development in arid areas. In this study the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) was modified by adding a soil salinity simulation to precisely describe the soil water and salt cycle, calculating capillary fluxes from shallow groundwater using readily available data, and simulating the effect of soil salinity on crop growth. The model combines an analytical solution of upward flux from groundwater using the Environmental Policy Integrated Climate (EPIC) crop growth model. The modified AWPM-SG was calibrated and validated with a maize field experiment run in 2016 in which predicted soil moisture, soil salinity, groundwater depth, and leaf area index were in agreement with the observations. To investigate the response of the model, various scenarios with varying groundwater depth and groundwater salinity were run. The inhibition of groundwater salinity on crop yield was slightly less than that on crop water use, while the water consumption of maize with a groundwater depth of 1 m is 3% less than that of 2 m, and the yield of maize with groundwater depth of 1 m is only 1% less than that of 2 m, under the groundwater salinity of 2.0 g/L. At the same groundwater depth, the higher the salinity, the greater the corn water productivity, and the smaller the corn irrigation water productivity. Consequently, using modified AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater.

Crop water requirements are crucial for agricultural water management and redistribution. Based on meteorological and agricultural observation data, the effective precipitation (P_e), water requirements (ET_c), and irrigation water requirements (I_r) in the maize growing areas of Inner Mongolia were calculated. Furthermore, climatic trends of these variables were analysed to reveal their temporal and spatial distributions. The research results are as follows: the average P_e of maize in Inner Mongolia during the entire growth period was 125.9 mm, with an increasing trend from west to east. The P_e in the middle growth period of maize was the highest and was small in the early and late growth stages. The P_e climate exhibited a negative slope with a decreasing trend. The average ET_c of maize during the entire growth period was 480.6 mm. The high-value areas are mainly distributed in the Wulatzhongqi and Linhe areas. The average I_r of maize during the entire growth period was 402.9 mm, and the spatial distribution is similar to that of ET_c. In each growth period, I_r showed an increasing trend. Supplemental irrigation should be added appropriately during each growth period to ensure the normal growth of maize. This study can provide an effective basis for the optimisation of irrigation and regional water conservation in the maize cultivation area of Inner Mongolia.

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 °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.

Drought is a major meteorological disaster that affects the growth of spring maize in Inner Mongolia. Understanding the spatiotemporal characteristics of drought is crucial for maintaining crop production. This study categorized Inner Mongolia into five climatic regions based on geography and climate characteristics: hyper-arid, arid, semi-arid, dry and semi-humid, and moist and semi-humid, reflecting Regions I to V, respectively. Based on data collected from 107 meteorological stations, the standardized precipitation evapotranspiration index (SPEI) was used to assess the characteristics of drought occurrence in different climatic regions during the spring maize growing season over the past 60 years, as well as the impact of drought on yield. SPEI decreased across all regions during growth periods, with mid-growth stages showing the smallest decline and a slight slowdown in drought severity. Spatially, 15 stations showed reduced drought during the early growth stage, which increased to 20 stations during the mid-growth stage. The overall drought trend of intensification was obtained across various climate regions, with Region I showing the most severe drought. The drought frequency during the growth period of spring maize ranged from 20% to 42%, and the drought frequency decreased from light drought, moderate drought, and severe drought to extreme drought. The drought range in each growth stage increased, with localized and regional drought dominating the region. The drought intensity also increased. Precipitation is the main factor affecting spring maize yield, and water replenishment during the early and middle stages of growth is crucial. These findings provide a basis for efficient water resource management in the region.