Ecological plasticity of winter wheat yield when cultivating on different predecessors in arid conditions of Eastern Caucasus

Relevance. The selection of the best winter wheat precursors that provide low yield variability in contrasting years is an important task of farming.Methods. Studies were carried out in 2017–2021 at the Prikumskaya Experimental Breeding Station in a 6-field crop rotation, where winter wheat was placed on bare and full fallow and semifallow. The aim of the research was to evaluate the precursors in different nutritional backgrounds from the position of low variability of yield, ecological stability and high adaptability to the conditions of the arid zone of the Stavropol Territory.Results. The hydro-thermal coefficient of summer-autumn period was 0,22 and of spring-summer period — 0,06 units drier than the average summer value. The pre-sowing period was especially unfavorable (HTC = 0.22). The stocks of productive moisture in a meter layer of soil in autumn were considerably below the norm on bare fallow in 40% of years of experiment and on other predecessors — in 80% of years. Yield of winter wheat varied from 2.43 to 4.46 t/ha on bare fallow on control, 2.86 to 4.93 t/ha — on fertilized variant, 1.98 to 4.72 and 2.15 to 5.35 t/ha— on ful fallow, 0.59 to 2.19 and 0.64 to 2.44 t/ha — on semifallow. And the environmental conditions index ranged from –0.51 to +1.52 and –0.64 to+1.43; from –0.90 to+1.84 and –1.10 to +2.10; from –0.72 to + 0.88 and –1.19 to +0.79 respectively. Maximum yields in all nutritional backgrounds were obtained on bare and full fallow. Only 1 year out of 5 was favorable as it had positive environmental conditions index values. The environmental plasticity ranged from 1.67 to 3.04. The highest yield variability (47.1%) and maximum stress tolerance (–1.6 –1.98 t/ha) was observed for the half fallow Semifallow. Bare fallow was the most flexible under stress conditions of cultivation as it had the highest yield (2.94–3.50 t/ha) and the lowest variability (26.4%) compared to other precursors. 