The aim of study was to develop rational irrigation regime for bulb onion. The study was conducted according standard techniques by B. A. Dospekhov, All-Russia Research Institute of Irrigative Agriculture and All -Russian Scientific Research Institute for Feed name V. R. Williams. The investigations revealed that in Rostov region most favorable irrigation regime for bulb onion is differentiated irrigation regime (until the end of leaf apparatus formation – 80-100 % of field capacity in the layer 0.4 m, later – 70-100 % of field capacity in the layer 0.4 m). This irrigation regime ensures the minimum water consumption rate (113.4 m³/t) under the insignificant decreasing of crop yield (1.5 t/ha). For the environmental restrictions and the necessity of resource-saving using the technique by G. A. Senchukov the relation of relative crop yield increasing for bulb onion to the level of water support was obtained: y = 0.43ln(x) + 1,0 with R²= 0.96, where y – the crop yield coefficient; x – the water support ratio of the agricultural land.
