Characteristics of spatial-temporal distribution of precipitation, water requirement and drought for summer maize growth period in Heilonggang Basin

Abstract: The severe over-exploitation of groundwater led to the problems of extreme water shortage and restricted irrigation in the Heilonggang Basin. Effective use of natural precipitation was one of the key approaches to solve the problem of water requirement for maize production in the Heilonggang Basin. The objective of this study was to analyze spatial-temporal distribution characteristics of effective precipitation and water requirement for maize production and define the water deficit region. Daily meteorological data from 18 surface meteorology stations from 1966 to 2015 were collected and phenological data of summer maize in 5 typical regions of the Heilonggang Basin were observed. The calculated index included effective precipitation, water requirement, the Crop Water Deficit Index (CWDI), the frequency of drought, and the correlation between water demand and meteorological factors during the maize whole growing period and 4 important stages. The water requirement of maize was estimated by using the Penman-Monteith equation of the Food and Agriculture Organization and crop coefficient method, and the crop coefficient of summer maize was identified by previous research of Hebei Province. The spatial distribution and evolution trend of drought for summer maize in different growth stages were analyzed by using the CWDI. Furthermore, analyzing the temporal and spatial distribution characteristics of the all calculated index in the whole growing period and each growth stage of maize was drew by the Inverse Distance Weighted (IDW) method of ArcGIS. The results showed that the range of annual effective precipitation in the summer maize growth period was from 292.89 mm to 361.56 mm, an average of the whole growth period was 326.46 mm, and the spatial distribution of effective precipitation during the whole growth period was showed a trend of 'high in northeast and low in the southwest'. The annual average water requirement for maize ranged from 362.82 mm to 444.04 mm with an average of 395.45 mm during the whole growing period, and the spatial distribution of water requirement showed a trend of 'higher in the south and lower in the north'. Total effective precipitation and water requirement during the whole growth period showed a downward trend year by year, and the climate tendency rates were -11.76 mm/10a and -6.26 mm/10a, respectively. Correlation analysis showed that the reduction in water requirement was related to a significant reduction in average sunshine hours and average wind speed. In the past 50 years, the drought frequency of summer maize during the whole growth period in the Heilonggang Basin was 48.30%. Among them, the proportion of drought-prone years of all the 4 growth stages were more than 33.3% in the southern regions and more than 66.6% during the kernel formation stage and grain filling stage both in the central and northern regions. The values of CWDI were less than 0.35 from the seedling stage to the ear developing stage and the water deficit regions were mainly concentrated in the central and southern regions. The average values of CWDI during the kernel formation stage and the grain filling stage were 0.49 and 0.41 respectively. The southern region of the Heilonggang basin was prone to light drought during the kernel development stage. The kernel formation stage and the grain filling stage were prone to occur drought in central and northern regions of the Heilonggang Basin, and the highest drought level reached moderate drought. Hybrid cultivars with higher drought resistance, shortened growth period and a higher rate of grain filling were recommended in the Heilonggang Basin to improve the drought resistance of summer maize, and soil water supply capacity could be increased through techniques such as subsoiling and straw-returning. This study could provide a theoretical basis for the efficient use of precipitation resources for summer maize in the Heilonggang Basin.