Effects of hydrothermal conditions on agrophysical properties of typical chernozem and crop rotation productivity in the system of organic farming

Relevance of research. Having the variability of hydrothermal conditions, the rate of plant life, the intensity of photosynthesis and evaporation and the activity of plant nutrient consumption change. As a rule, the optimization of the water-air regime of the soil by conducting various types of amelioration makes it possible to significantly reduce the negative effects of adverse weather conditions and ensure high sustainability of agroecosystems. However, with regard to the requirements for organic agriculture in the regions with a shortage of water supply without sufficient water resources and without the use of fertilizers to effectively conduct agricultural production is problematic. Thus, the establishment of the patterns of the dynamics of agrophysical soil properties, taking into account their impact on the bioproductivity of agrophytocenoses under variable weather conditions is the theoretical basis for solving the problem of increasing agricultural sustainability, in particular using only natural fertility and obtaining organic crop products. Purpose and objectives of research: To establish the mechanisms of changes in the nutrient regime of typical chernozem, its agrophysical properties and crop yields in different crop rotations in relation to the dynamics of agrometeorological factors under the conditions of insufficient water supply in the eastern Forest-Steppe of Ukraine; to evaluate the productivity potential of cereals and grain crops in the system of organic farming without the use of mineral fertilizers. Research methods and techniques. Evaluation of the changes in agrometeorological resources of the territory was carried out using the method of mathematical and statistical analysis of the indicators of heat and moisture supply conditions: climatic water balance and precipitation. The data obtained from the stationary experiment were processed by the methods of system generalization, correlation, economic, calculation and comparative analyzes. Research results and main conclusions. Based on the information obtained in the course the stationary agrotechnical experiment it was established that the soil density changes over the years and depends on the hydrothermal conditions with the approximation certainity of (R2) 0.75. The inverse relationship between the specific weight of the soil and its water conductivity in terms of crop rotations with R2=0.8-0.9, by years with R2=0.6 was revealed. The variation coefficient of legumes yield was 30-33%, winter wheat – 33-37%, spring barley – 36-37%, which are the indicators of its low stability over the years. Crop yields, depending on the weather conditions of the year, also fluctuated significantly: peas between 0.8-3.2, lathyrus – 0.8-2.6, winter wheat – 0.6-6.8, buckwheat – 0.6-1.9, spring barley – 0.6-3.5 t/ha. Crop rotation with peas in terms of productivity of 2.4 t/ha of grain on average outperformed the others (2.2 and 2.0 t/ha) while maintaining the patterns of fluctuations of this indicator in relation to hydrothermal conditions. Having the average statistical selling price, the yield per 1 ha of crop rotation area of all studied crop rotations was almost the same with the fluctuations in the unfavorable years of 27-35 c. u./ha, in favorable ones – 97-104 c. u./ha, with the average value of 66-73 c. u./ha. If we assume that the selling price of organic products will be 25% higher than usual, the average annual yield will triple. Prospects for further research should correspond to the global trend of scientific research aimed at developing conceptual bases for the effects of hydrothermal conditions on agrophysical soil properties, taking into account their impact on bioproductivity of agrophytocenoses as a theoretical basis for solving the problem of increasing agricultural sustainability, in particular, using only the natural fertility of the organic-oriented model of developing the agricultural sector of the economy.