Response of spring wheat yield to changes in hydrothermal conditions expressed by drought indices

This paper examines the relationship between spring wheat yield and various moisture/drought indices. The study utilizes field data of spring wheat yield from 1986 to 2022, obtained at the research station in the central forest-steppe of the Ob region. The following indices were analyzed: Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Ped’s drought index (S) (both considering soil moisture – S _T,R,E and without it – S _T,R ), Selyaninov’s hydrothermal coefficient (HTC) and normalized HTC (HTC _norm ). Results suggest that maximum intensification levels and planting wheat as the first crop after fallow, along with moldboard tillage contribute to maximum spring wheat yield. Yield is also affected by abiotic factors, primarily the heat-moisture ratio. The relationship between yield and heat-moisture conditions from May to September varies depending on treatment levels. In May, regardless of intensification and soil treatment, the yield of the third crop after fallow shows the greatest dependence on hydrothermal conditions. In June, air temperature is a limiting yield factor, with crops placed after fallow showing higher sensitivity. In July, significant correlations were observed between yield and at least one of the hydrothermal indices. Ped’s drought index proved to be the most informative for both the entire vegetation period and individual months; instances of low yield coincided more frequently with droughts identified by Ped’s compared to other indices. Correlation coefficients between yield and Ped’s index considering soil moisture (S _T,R,E ) were higher than correlation coefficients between yield and other indices, suggesting its potential for predicting wheat yields.