The text of Ruins of Warsaw mentions scythes as farm implements--that's a fairly labor-intensive method of harvesting the grain.
Anybody have an idea how difficult it would be to cobble together a couple of McCormick Reapers to bring the Warsaw harvest in while allowing most of the hand labor to go to shoring up the fortifications? And about how many would be needed to bring their harvest in within 2-3 days? Nothing really fancy, don't need the machines to thresh or bind the stalks just to cut them down. If the city's jackleg mechanics have been scrounging the debris for useable metal, I am sure they would have come across a few bicycle frames by now. Or perhaps Adam Rataj has some part of a consignment of bikes on board the barge from the Krakow industries. The grumpy genius ship's mechanic could use the Krolowa's machine shop to transform the bikes into harvester frames. Research at the New/Old City library could provide essential details as to how to make the frames strong enough to function correctly. Disinformation can be spread that the frames are designed to help people take their belongings out of the city when the Baron("who will surely be the victor") assaults the city. Lots of adventure potential here.
I've been toying with the idea of trying to harvest just the tops of the cereal stalks, leaving the rest of the plant upright. When the Baron's forces come a-marchin' through the rye, so to speak, lob some WP rounds into the dry stalks, creating a ring of fire around the units. Troops, by the numbers, _PANIC_!!!!!! You could probably leave the corn on the stalks--it would cook the ears and provide a meal post battle.
THen again, marching through a cornfield with lots of downed ears underfoot is like dancing on rolling pins (something we found out at the 135th Antietam ACW reenactment).