| Natural characteristics such as precipitation and evaporation in Liaoning have obvious spatial variability,and irrigation management of the same crop in different regions is bound to differ.In order to grasp the degree of drought in different regions of Liaoning and obtain the irrigation management patterns of spring maize in different regions,based on the day-by-day meteorological data of 24 typical meteorological stations in Liaoning from 1951 to 2018,we used R language programming to calculate the monthly time-scale SPEI during the reproductive period of spring maize and used Arc GIS natural intermittent point grading method to divide the drought in Liaoning;meanwhile,we used the spatial distribution of effective precipitation,reference crop evapotranspiration,spring maize crop coefficients,spring maize water requirements and spring maize irrigation water requirements during the whole reproductive period and each reproductive period were analyzed using Arc GIS kriging spatial interpolation method;the hydrological representative years was selected using MATLAB,the irrigation schedule of spring maize in different regions of Liaoning in different hydrological years was developed by combining the drought division of Liaoning and the irrigation water requirements of spring maize during the reproductive period.The main findings are as follows.(1)Based on the monthly time scale SPEI,the frequencies of mild drought,moderate drought,and severe drought are 12.64-22.37%,6.91-13.77%,and 5.06-7.36% during the spring maize reproductive period in Liaoning.The frequencies of mild drought and moderate drought showing an overall decreasing trend from west to east,and the frequency of severe drought or more is mainly distributed in the western part of Liaoning.Based on the mean SPEI values during the reproductive period of spring maize,spring maize drought in Liaoning can be classified as: special drought,severe drought,moderate drought and light drought.(2)The effective precipitation is 261.38-572.65 mm during the spring maize whole reproductive period in Liaoning,showing an overall increasing trend from west to east;the evapotranspiration of reference crop is 436.03-619.56 mm during the spring maize whole reproductive period in Liaoning,showing an overall decreasing trend from west to east;the crop coefficients of spring maize is 0.696-0.725 during the whole reproductive period in Liaoning,showing an overall increasing and then decreasing trend from west to east;the water requirements of spring maize is 302.13-449.69 mm during the whole reproductive period in Liaoning,showing an overall increasing and then decreasing trend from west to east;the irrigation water requirements of spring maize is 0-182.20 mm during the whole reproductive period in Liaoning,showing an overall decreasing trend from west to east,and no irrigation is needed in eastern Liaoning.The spatial distribution characteristics of irrigation management-related indexes in spring maize in Liaoning are approximately the same as those in the whole breeding period.(3)The irrigation quotas for spring maize in extra-dry areas,heavy-dry areas,medium-dry areas,and light-dry areas are 128.80-290.26 mm,53.31-266.45 mm,28.20-178.75 mm,and 0-154.56 mm in different hydrological years.In addition,in the early stage of fertility,spring maize does not need irrigation in heavy drought areas with partial and abundant water years and light drought areas with dry and flat water years;in the rapid growth period,spring maize does not need irrigation in extra dry areas with partial and abundant water years;in the middle stage of fertility,spring maize does not need irrigation in heavy drought areas with abundant water years and medium drought areas with partial,flat and abundant water years;in the late stage of fertility,spring maize in different regions of Liaoning does not need irrigation in different hydrological years.This irrigation schedule is the irrigation schedule for spring maize in different regions of Liaoning in different hydrological years.The findings of the study provide a theoretical basis for the selection of spring maize irrigation management mode in the construction of high standard farmland in Liaoning. |
