An important condition of rational usage of irrigation water is the determination and regulation of water consumption by grain maize at main growth phases providing maximum product yield per unit water supplied. The establishment of water consumption for growth periods will allow planning the irrigation regime and determining rates of water consumption and discharge. The research has shown that bioclimatic coefficients in all cases increase beginning with sprouting stage and maximize at the

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... e of paniculation, milky-wax ripeness, and then decreases again. The obtained data were used to calculate the bioclimatic coefficients of water consumption by grain maize using the interphase vegetation periods, from sprouts to ripening. Thus, the implemented calculation methods of total evaporation are local, and increased calculation accuracy requires determining them experimentally in specific climatic conditions.