Investigations were made on the seasonal water requirements of annual onion cv. Santana grown under optimal schedule of irrigation and water stress. Three variants with different irrigation rates (1.00 IR, 0.75 IR and 0.50 IR) were studied. A system for microsprinkler irrigation was used, the time of irrigation being determined by estimating soil moisture. The first irrigation was done after sowing and the last - at the lodging of onion leaves. The actual evapotranspiration for the three irrigated variants was established. Its total value in the optimal variant over the irrigation season was 337,84 mm. The evapotranspiration productivity varied in the range of 8,58 - 14,55 kg/mm. The „relative yield - relative evapotranspiration” relationship was determined.
