ASSESMENT THE GROWTH DYNAMICS OF SOYBEAN YIELD AGRO-ENVIRONMENTAL CATEGORIES
Authors: Tolmachova A. V. 
Published: June 2023

In this paper a model of assessment the growth dynamics of soybean yield agro-ecological categories was proposed and a generalized characteristic of agro-climatic conditions of soya cultivation productivity in the forest-steppe zone of the Ukraine was performed. Purpose. Soybean is the most common, legume and oilseed crop of our planet. This thermopiles leguminous plant is the short-day plant of the monsoon climate. Subject of the study. Regularities of the agro-climatic conditions influence on the formation of agro-ecological levels of soybean yield. Purpose of the work is to develop a model and assess the impact of agro-climatic conditions on the soybean yield formation and modeling this influence. Methodology.  The theoretical basis of the study was to use the basic model of the assessment of agro-climatic resources of crops productivity formation by A.N. Polevoy, based on H.G.Tooming concept about the maximum crop productivity. The model is based on the concepts of four levels of agro-ecological yield categories: potential yield (PY), meteorologically possible yield (MPY), actually possible yield (APY) and yield in the production (YP). Also we will consider the generalized characteristics of cultivation agro-climatic conditions: degree of favoring meteorological conditions of crop cultivation and efficiency of agro-climatic resources use. On the basis of mean annual meteorological and agro-meteorological data, as well as using information on organic and mineral fertilizers application, the formation of different agro-ecological levels of soybean yields in the Ukraine was modeled. Finding. Calculated values allowed us to estimate the dynamics of PY, MPY, APY and YP growth and the course of decadal sums of PAR during the growing season, which were calculated for forest-steppe zone of the Ukraine. The maximum value of PY, MPY, APY, YP growth and PAR sums reached in the eighth decade and are 225.7 g/m2 ∙ dec., 208.9 g/m2 ∙ dec., 126.9 g/m2 ∙ dec., 43.4 g/m2 ∙ dec. and 11.8 kJ/ cm2 ∙ dec. respectively. By the end and PAR sums of the growing season the growths and PAR sums are reducing. Calculated values allowed us to estimate the dynamics of hydrothermal regime of soybeans. Evapotranspiration (E) and evaporation (E0) have a well-defined trend. With increasing air temperature and precipitation the evapotranspiration may increase or decrease. The ratio of evapotranspiration to evaporability (E/E0) characterizes moisture availability of crops and varies from 0.83 relative units to 0.6 relative units by the end of the growing season. On the basis of calculations made the assessment of generalized characteristics of agroclimatic conditions and productivity of soybean cultivation in the forest-steppe zone of the Ukraine. The highest values of grain MPY, grain APY, grain YP observed in forest-steppe areas, the lowest values are typical for areas of Southern Steppe. The highest degree of favoring the meteorological conditions (Km) for soybean cultivation observed in Polesye, the smallest value (Km) is in Southern Steppe. The assessment of the level of agro-climatic resources use efficiency (Kakl) for soybean cultivation showed that the highest value observed in the forest-steppe areas, the lowest value is in Northern Steppe. Conclusions. Thus, using the simulation we evaluated the impact of agro-climatic conditions on the dynamics of agro-ecological yield growth levels of soybean crop and estimated agro-ecological categories of grain yield, as well as estimated degree of favoring agro-climatic conditions for the soybean cultivation in the forest-steppe areas of the Ukraine.