An example of how little good...

An example of how little good the Germans received from the Ukraine after the Nazis conquered the territory. By the first week of March, this was reported in the Time magazine.

Last week, as the Wehrmacht reeled farther & farther back into the Ukraine, the Germans were fast losing this vast (172,000 sq. mi.), heavily populated (31,000,000) territory, and the Russians were regaining one of their greatest centers of wealth.

… One of the first tasks of German engineers was to repair and restore highways and bridges, to convert railways as far as the Dnieper to the narrower European gauge. Restoration of reconquered railways is bound to be a major problem for the Russians.

(as they retreated)The Russians had destroyed 67,000 tractors, 18,500 heavy trucks, and 22,000 combines before they gave up the Ukraine. One result was that Ukrainian farmlands produced very little for the Germans. They were able to bring in about 5,000 tractors, and a few thousand plows. By forcing prisoners and peasants to work the fields 17 hours a day, the Germans were able to plant and harvest about 300,000 tons of grain, all types in 1942 (in 1937, the Ukraine produced 10,000,000 tons of wheat alone).

See:

World Battlefronts: BATTLE OF RUSSIA: What Hitler is Losing - TIME

So much for "Russian soil for the Teutonic plow". The new lebensraum gained them next to nothing.

 

It sounds like it would take a decade or longer to fully restore ag production even if victorious. The viable reasons for a German attack seem to get slimmer and slimmer.