Corn stands up pretty well to the Ukrainian winter although I wouldn't recommend leaving extensive areas to be harvested in the spring.
The USDA estimate for 2016 Ukraine corn is recorded as a tentative 26mmt which is up around 3mmt or 11% on 2015 but down on 2013 and 2014.
It's worth keeping in mind corn plantings in 2013 and 2014 spiked as the government policy at that time encouraged planting of corn to increase exports and to generate foreign revenue.
So if anything the hectares planted in 2015 and 2016 has probably returned to the trend before government "policy" skewed numbers upwards.