a plain in the European part of the USSR, situated between the Central Russian and Volga uplands, extending from the Oka River in the north to the Kalach Upland in the south. The plain’s northern and central parts are called the Tambov Plain.
The plain has a flat, rolling relief consisting of watersheds with heights of 150–180 m alternating with broad terraced valleys, ravines, and sinkholes. It is composed of deeply eroded moraine overlaid by sand in the valleys and by mantle and loess-like loams in the watersheds. The Oka-Don plain is situated principally in the forest-steppe zone. Precipitation totals 450–500 mm per year. The soils are predominantly gray forest and chernozem. The plain is one of the important agricultural regions of the European part of the USSR.