Water consumption by uneven-aged winter wheat plants in arid conditions of the Steppe

It was established that there are significant changes in hydrothermal indicators over the past thirty years in the south of the Steppe. During the growing seasons of 1963/64–1989/90, the average annual air temperature was 9.6 °С, in 1990/91–2019/20 – 11.3 °C. Average annual precipitation in 1957/58–1989/90 was 456.1 mm, 1990/91–2019/20 – 400.5 mm. Thus, the increase in climate aridity over the last thirty years is obvious: the average annual precipitation has decreased by 55.6 mm, and the average annual air temperature has increased by 1.7 °C. During the growing seasons of 1990/91–2019/20, scientific research found that water consumption by wheat plants after black fallow during the growing season decreased to 2536–2811 m3/ha in the Steppe zone. Moisture was most efficiently consumed by crops at sowing on September 25 (background N40P40K40, seed rate – 4.5 million germinable seeds/ha): total water consumption was 2605 m3/ha, water consumption coefficient – 428 m3/t, grain yield – 6,08 t/ha. According to 28-year-old data, it was found that the available moisture reserves in the 0-10 cm soil layer on black fallow, as the most stable predecessor on water availability of soil, equaled 10.2 mm and ensured almost annual obtainment of full winter wheat seedlings. It was found that the winter wheat plants did not evenly consume moisture during the growing season: in the autumn period – 8.0–19.2 % of the total water consumption, resumption of spring growing season – beginning of stem elongation – 28.3–30.9 %, stem elongation – beginning of heading – 22.1–24.2 %, heading – full ripeness – 30.0–36.9 %. According to the research results, it was proposed the measures to minimize the negative impact of further climate aridity increase by an increase in the autumn-winter precipitation absorption by soil, an improvement of the agrophysical soil properties and its water permeability, the introduction of varieties with a more pronounced xeromorphic structure and an increased level of adaptation to arid conditions of the Steppe zone and resistance to abiotic stress factors. Key words: predecessors, sowing dates, productive moisture reserves in the soil, water consumption, yield, winter wheat, water consumption coefficient.