Agroecological drivers of winter rye (Secale cereale) yield spatio-temporal variation

The study of yield-limiting factors of rye, a typical European cereal, is a crucial concern today as it significantly impacts global food safety. The objecive of the study was to determine the contribution of agroecological factors, namely bioclimatic variables, soil parameters, and landscape diversity, to the variation of rye yields in the central and northern regions of Ukraine, which is one of the world’s five largest producers of this crop. A symmetric log-logistic model was used to describe the dynamics of rye yields, and the parameters of this model can be used to analyze the spatial dynamics of yields, in particular, such characteristic points of the yield model as: the lower limit of the response (the lowest yield level); the upper limit (the highest yield level); the slope of the response curve in the vicinity of the inflection point, which shows the rate of yield change over time, ED50 – the time required to reach half of the maximum yield growth. In the preliminary principal component analysis, we identified 4 climate principal components and 6 soil principal components. Landscape diversity was assessed based on the Shannon index and distance to the protected areas. The results of the regression analysis revealed a statistically significant relationship between the parameters of rye yield and the identified environmental drivers. Among the rye yield parameters, the highest sensitivity to environmental factors was the upper yield limit (70%), and the lowest was the rate of yield increase (25%). Only the highest rate of yield growth demonstrated liner dependence on the Shannon index. Among the soil factors, the most influential for rye yields was the particle size distribution and especially the sand content. The rye yield parameters were primarily influenced by the variability of the temperature regime throughout extreme periods of the year and contrast in the temperature conditions. The yield parameters of rye were contingent upon the diversity of the landscape cover. The correlation between almost all yield characteristics and landscape-ecological diversity was not linear, leading to the identification of an optimal level of diversity in natural protected areas which results in the best rye yields.