Among the complex groups of the factors that shape the state of an agro-ecosystem and influence its functioning are the climatic conditions.The relevance of the problem is determined by the ongoing changes in certain climatic parameters, which form the functioning of the agro-ecosystems and predetermine its status, conditions and limits of organisms’ tolerance. The climatic factors determine the crop productivity. Therefore, the main issue in the study of the anthropogenically transformed systems is the determination of an agricultural ecosystem status depending on the impact of changing environmental conditions (in particular, the environmental factors).

As to this problem, Y.P. Didukh and O.G. Tarariko argue that the state of the agri-ecosystem components influenced by changing climatic parameters varies considerably. Consequently, it is possible to reach high crop capacity if the growth conditions are in accordance with the species biological requirements. And on the contrary, incompatibility between the natural conditions and the requirements of living organisms leads to low yield capacity crop production.

The aim of the article is to study the impact of climatic factors in Lubny district of Poltava region on winter wheat yield capacity as winter wheat is the main grain crop of the area.

In the research there was performed the analysis of long-term (1996-2015) data concerning winter wheat yield rates and the meteorological parameters, which characterize the temperature and moisture regimes in Lubny district of Poltava region. The study showed the interrelation between climate conditions and winter wheat productivity. Using the data collected by Lubny meteorological station we calculated the classical index of heat supply in the region during the period of 1996-2015. In the course of the research the analytical methods, long-term statistical analysis, methods of comparison and logical generalization were applied.

The analysis shows that the unevenness of the dynamic changes in winter wheat yield capacity is determined by the interrelation of the climatic territorial conditions, which considerably influence the performance of all the components in agro-ecosystems. Taking into account the significant impact of the agro-climatic factors on the crop plantings, plant heat supply index, moisture regime, crop damage with diseases, as well as weed contamination index have been analyzed over a 20-year period and showed their influence on winter wheat productivity have been shown.

Analyzing the dynamics of winter wheat capacity depending on climatic changes within a 20-year period, it has been found that it ranged from 0.8 t/ha to 4.9 t/ha. Whereas in 1997, 2000, 2003 the yield capacity dropped to 1.8, 1.0 and 0.8 t/ha, respectively, and that was presumably caused by the adverse weather behaviour during the above-mentioned years. In particular, the winter season in these years was characterized by the unstable changes in certain climatic parameters. As a result, there was observed the formation of thick ice crust. The reduction of the crop plantings comprised 25-32% in the early spring of 2000, which led to the increase in weed contamination. At the same time, heavy rains in June with strong winds and hail caused crop lodging.

Taking into consideration the low winter wheat yields in 1997, 2000, and 2003 it was necessary to analyze the disease infestation and weed contamination indexes. The statistical data showed that weed contamination of winter wheat comprised 2-3 points out of 3. Moreover, the unfavourable weather conditions of the summer season in 1997 caused a fungal disease (Septorianodorum).

The analysis of data which embraced a 20-year period (1996-2015) showed a tendency to the increase in classical index of heat supply and the reduction of annual precipitation compared to the long-term norms, which influenced the winter wheat productivity.

Further changes in climate parameters may cause the changes in the weather conditions in the cultivation area and lead to considerable reduction in the crop production. Therefore, to obtain permanent high winter wheat yields in the forest-steppe zone it is necessary to take into account the climatic resources of the region.

Key words: winter wheat, crop productivity, heat supply index, moisture content index, weed contamination, agro-climatic resources.