The objective of the study was to investigate the impact of biologically optimal (70-80-70 % of field capacity (FC) in the soil layer of 0.5 m), water-saving (70 % FC in the soil layer of 0.5 m), and soil-protective (70 % FC in the soil layer of 0.3 m) irrigation modes, different backgrounds of mineral nutrition, and plant population for corn at the plots of hybridization. The original parent form Êðîññ 221 ÌÂ (Kross 221 MV) for hybrid F1 Ñèâàø (Sivash) has grown in a short three-field rotation (winter wheat-corn-soybean) in the southern part of the Steppe of Ukraine at the dark-brown medium loamy slightly alkaline soil with low content of nitrogen, medium content of phosphorus, and high content of potassium. Two years of the study on moisture deficit were medium dry (amount of precipitations 117.1-157.6 mm), one year – medium (amount of precipitations 129.6 mm). The largest water consumption of corn, 4370 m³/ha, was observed at the variant with biologically optimal irrigation mode. The main zone of moisture exchange was the soil layer 0-100 cm, the ratio of soil moisture use in this layer was from 24 to 29 %, the ratio of precipitation use – 31-33 %, the ratio of irrigation water use – 38-45 %. On average for years of the study, the biologically optimal irrigation mode has provided the highest seed yield of self-pollinated lines of corn. The recommended fertilizing dose is N120P90, plant population – 80 thousand plants per hectare. Fertilization has increased the seed yield of parent form at the grain moisture of 14 % by 1.30-1.41 t/ha versus to the variant without fertilization. Crop crowding from 40 to 60 and 80 thousand plants per hectare at the plots of hybridization increased the yield by 0.81-1.44 t/ha on average for the factor. The optimal watering of corn provided to obtain 7.4 t/ha of corn seeds. Irrigation at the soil moisture at 70 % FC in soil layers of 0.3 and 0.5 m decreased the yield by 0.1-0.84 t/ha on average for the factor.
