Statistical methods to study the relationship of stability of dynamics and fluctuations in winter wheat yields with solar activity

Subject. The article addresses the influence of solar activity cycles on the stability of dynamics and fluctuations of winter wheat yields, on the Orel Oblast case. Objectives. The purpose of the study is to explore the relationship of solar activity in Wolf numbers with fluctuations in winter wheat yield; provide a quantitative measure of the relationship. Methods. We employed statistical methods for measuring trends in dynamics, established indicators of stability and fluctuation of yields, used time series correlation, the M. Kendall's method by the number of turning points to determine the type of fluctuations, tabular and graphical methods. Results. We presented time series of winter wheat yields for 1954–2022 (for 69 years). They include six 11-year cycles of solar activity. Taking into account the historical, socio-economic, agrotechnological conditions of development and achievements of breeding, we examined the time series of winter wheat yields for several periods. For 1954–2022, winter wheat yields increased 3.8 times, the average annual absolute increase was 10 times. The coefficient of determination confirmed that 11.2% of fluctuations in winter wheat yield were due to the influence of solar activity. Conclusions. The study of the variability of winter wheat yields showed that for 22-year cycles of solar activity, only 2% of yield fluctuations were due to differences in deviations of annual Wolf number levels from the average annual level.