The union said farmers had threshed 4.3 million hectares of wheat with an average yield of 4.0 tonnes per hectare.
The union's statement said farmers had harvested a total of 25.7 million tonnes of grains and oilseeds so far.
The agriculture ministry said in a separate statement the volume included 23.4 million tonnes of grains with an average yield of 3.82 tonne per hectare.
That included 5.3 million tonnes of barley, 243,700 tonnes of peas and 3.1 million tonnes of rapeseed, harvested from 98% of the sown area.
Ukraine, a major global grain grower and exporter, harvested a record 86 million tonnes of grain in 2021 including 42.1 million tonnes of corn and 32.2 million tonnes of wheat.
The government has said that this year's harvest could fall to about 65-67 million tonnes of grain and oilseeds.
(Reporting by Pavel Polityuk; editing by Jason Neely)
