AUTUMN GROWTH AND DEVELOPMENT OF WINTER WHEAT PLANTS ON THE IRRIGATED LANDS DEPENDING ON HYDROTHERMAL CONDITIONS, VARIETIES AND TERMS OF SOWING

Actuality. For the last few years the instability in grain productions in the Steppe zone has been observed that is mainly connected with the fluctuations of agrometeorological conditions and global climatic change. Climate change made corrections in terms of sowing of winter crops, which are one of the main factors of technological process, which productivity of the crops depends on. Goal. To determine the influence of agrometeorological conditions, varieties and terms of sowing on the growth and development of plants during the autumn period of vegetation when cultivating winter wheat varieties on irrigated lands. Methods. The researches were conducted at the Institute of Irrigated Agriculture NAAS using the methodology of field and laboratory experiments on irrigated lands (IOZ  NAAS, 2014). Results. During the study period it was determined that the hydrothermal conditions and the duration of the autumn period for winter wheat vegetation were significantly different. When sowing on the 20th of September, on the 1st of October, and on the 10th of October, the duration of the autumn vegetation period in 2016 was 56, 46 and 36 days, in 2015 - 100, 90 and 80 days and in 2017 - 114, 104 and 94 days respectively. When sowing on the 20th of October, winter wheat plants vegetated during 26, 70 and 84 days, respectively. Sowing terms affected winter wheat sprout population in different ways - when sowing on the 20th of September, it averaged to 372 plants/m2, on the 1st of October - 407 plants/m2, on the 10th of October – 386 plants/m2 and on the 20th of October - 392 plants/m2. It was determined that at different terms of sowing the plants entered in winter period with uneven growth and development. When sowing on the 20th of September all the varieties in autumn tillered, and in average for three years they created 4.1-5.0 shoots, developed more herbage mass of 713-761 g/m2 in comparison to other terms of sowing. The later wheat was sown, the less the plant tillering was, therefore, less herbage mass was formed. Conclusions. Agrometeorological conditions of autumn period and terms of sowing significantly affect the population of sprouts and growth processes of the plants of current winter wheat varieties. The highest plant population of all the varieties was formed when sowing on the 1st of October, the least one was formed by the varieties Mariia and Kokhana at early sowing on the 20th of September, and variety Ovidii – at early sowing on the 20th of September, and at late sowing on the 20th of October. That is, the Ovid variety is more responsive to the terms of sowing and to the deviation from the optimal (October 1) and leads to a decrease in the sprouting density. When sowing on the 20th of September and on the 1st of October all the varieties tillered intensively in autumn time, and they formed 4.1-5.0 and 3.3-3.7 shoots, respectively, developed more herbage mass comparatively to other terms of sowing -  713-761 and 313-381 g/m2 respectively. Having these terms of sowing the most intensive tillering was observed on the varieties Mariia and Kokhana, and when sowing in delayed terms no one variety had an advantage over the others.