The article presents the results of studies on the effects of hydrothermal conditions of the growing season on yield of green mass corn hybrids that are in different maturity groups.

In modern conditions, the significance is the increase in corn production by creating a silage pipeline of cultivation in the area of Central forest-Steppe zone of Ukraine hybrids that have different maturity groups. Proper selection of plastic hybrids of corn silage direction, with stable yields, will not only increase productivity of this culture, but also get high quality silage at content of dry substance in plants 28-30 % with part of ears 45-50%. Global and regional climate changes necessitate revision of the basic principles of growing corn for silage, including the use of new hybrids of different maturity groups.

During the growing season of maize plants within three years of research hydrothermal conditions were different, especially in the period of formation, filling and forming grain that gives an opportunity in more depth to estimate plasticity of investigational hybrids and expose their biological and agroecological features of growing.

The data of our research show that favorable conditions for normal growth and development of corn were only under moisture years (2011 and 2013) when HTC ranged from 1,03-1,88. The green mass yield formation of early hybrid Tovtryanskiy 188 SV was at level 44,0-45,4 t/ha, mid-early hybrid Bilozirskiy 295 SV – 48,3-49,7 t/ha, middle hybrid Monica 350 MV – 52,7-54,1 t/ha and middle hybrid Bystriza 400 56 MV,5-58 6 t/ha.

In droughty 2012, when the hydrothermal coefficient decreased to 0,24-0,92, yield hybrids on average diminished on 9,9-14,5 t/ha or in relative terms 18,8-25,1%. Herewith most middle-maturing forms reduced the productivity, that testifies their plants have an increase demand to moisture conditions. However, the trend of increasing the yield of early maturing forms to medium preserved in all the years of research.

In our study found a strong correlation between the hydrothermal regime during the growing season and the processes of grain formation in hybrids of different maturity groups, especially in the second half of the growing season (r = 0,72-0,86), indicating a strengthening of the role of climatic factors in forming the corn productivity in the forest-Steppe zone of Ukraine. Clear evidence of this is oscillation of the productivity of green mass of hybrids after years depending on the terms of moistening.

In years with the deficit of moisture and uneven distribution of precipitations during a vegetation period dependence between the sum of precipitations and productivity has the clearly expressed character.

All investigated hybrids of corn negatively react on worsening of moisture terms, especially middle-maturing Monica 350 MV and medium Bystrica 400 MV. Reduction HTC in July 2013 to 0.67 resulted in shortage of green mass yield of the hybrid: 1,4-2,2 t/ha compared to 2011.

Selection of corn hybrids, genetic potential of that maximally answers the agroclimatic conditions of the forest-Steppe zone of Ukraine, is one of the effective methods of modern crop that allows increasing productivity of crops by activation of biological potential of agroecosystems and their constituent elements at all levels, replacing a large part of human energy internal energy of biological processes.

The central areas of the forest-Steppe zone of Ukraine are characterized by unstable moistening, and the degree of moisture determines different levels of the productivity. In moist years the yield of green mass of corn is approached to 58.6 t/ha and in droughty to 34.5 t/ha. Middle-maturing hybrid Monica 350 MV and medium Bystrica 400 MV have the highest productivity but in unfavorable on agroclimatic indexes years, they significantly reduced productivity compared with more early maturing forms.

Key words: corn, productivity, green mass, hybrids, hydrothermal coefficient (HTC).