Jar - Plon niesiemy plon
“Plon niesiemy plon” (“Harvest, we are bringing harvest”) is a traditional song sung during Dożynki (Harvest Festival).
In Poland Dożynki is folk festival combined with a ceremonial thanksgiving for the completion of harvest and field work. In pre-Christian times - the ethnic Slavic festival. It’s celebrated during the autumn equinox (September 23).
People in Belarus also celebrate Dazhynki.
A list of Harvest festivals around the world: http://en.wikipedia.org/wiki/List_of_Harvest_Festivals