http://www.tomatoville.com/search.php?searchid=2532456
In the above search for RKN's you'll find a lot of information about what others have used in the past, ranging from shrimp shells to Ebon rye to solarization, and yes Marigolds,and much more.
And reports back on how effective,or not.
Good to remember that RKN's prefer sandy soils since they migrate from one sand grain to the next, via the water shell around each grain,which allows them to spread easily in such sandy soils. Then taken up by the plant roots.
Possible solution and not my own but the experiences of many others? If you have sandy soils add lots of good mulch each year so as to seperate the sand grains making RKN movement more difficult.
Carolyn