SEED PRODUCTIVITY OF ALFALFA VARIETIES DEPENDING ON THE CONDITIONS OF HUMIDIFICATION AND GROWTH REGULATORS IN THE SOUTHERN STEPPE OF UKRAINE

The aim of the study was to determine the effect of humidification conditions (drip irrigation and no irrigation) and growth regulators (Agrostimulin, Garth, Lucis, Emistim C) on the seed productivity of alfalfa varieties Unifro and Zoryana. The study was carried out during 2012-2015 at the experimental field of the Institute of Irrigated Agriculture of NAAS on the dark-chestnut soil in the conditions of the Steppe zone. The yield of alfalfa seeds in the conditions of natural humidification was (by the years of life) 154; 471; 235 kg/ha, and drip irrigation increased them to 207; 640; 538 kg/ha. Application of the growth regulators favored for the increase in the seed yield: 161-171; 479-492; 245-256 kg/ha without irrigation, and 217-230; 653-668; 559-583 kg/ha at drip irrigation. The highest yield of 175; 497; 261 kg/ha and 236; 674; 594 kg/ha was obtained in the variants with Garth growth regulator application. Drip irrigation increased the root mass from 1.61 to 2.03 t/ha. The preparations stimulated the root mass accumulation, mostly at drip irrigation, by the years of the crop life: Agrostimulin - 2.46; 5.36; 6.78 t/ha, Lucis - 2.50; 5.61; 7.05, Emistim C - 2.42; 5.28; 6.72 and Garth with the maximum indices - 2.53; 5.73; 7.25 t/ha. Atmospheric nitrogen fixation increased from the first to the second year of the crop life, and further decreased to the third year of the herbage life. Strong correlation ties between the seed productivity and root mass accumulation (r= 0.932-0.984), atmospheric nitrogen fixation (r= 0.960-0.975) and between the root mass accumulation and atmospheric nitrogen fixation (r= 0.990-0.996) were determined.