Regardless of how well this works, there is some thought
that shrimp shell meal may help with nematode control.
(The idea is that something feeds on the chitin in the shrimp
shell meal, and once it runs out, its next best food is the
nematodes.)
I came across it at Peaceful Valley:
http://www.groworganic.com/item_F196...theses=3161146
Could be part of a multi-pronged approach to nematode control
(using shrimp shell meal as part of your regular soil amending).