Or mashed yellow (some say Swedish) turnips. It is traditional Norwegian fare, and mandatory with the dried-and-smoked lamb ribs (pinnekjøtt) that take us through the darkest nights of winter.
Your sentence is indeed stumping, and would go something like this: "so, you will be clearing cold turnip mash in the barn?"... hardly enlightening, but that's what it says. Rydde means to tidy up, clear away, put things in their places - not stuff you would normally do to mashed yellow turnips.

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Note added at 1 hr (2006-09-22 12:57:06 GMT) Post-grading
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For the record, here is what wikipedia says about kohlrabi - which is NOT the stuff from which the traditional Norwegian kålrabistappe (or even kålrotstappe) is made: http://en.wikipedia.org/wiki/Kohlrabi